Article

The Chemical Composition of Xylem Sap in Vitis vinifera L. cv. Riesling During Vegetative Growth on Three Different Franconian Vineyard Soils and as Influenced by Nitrogen Fertilizer

January 2000
American Journal of Enology and Viticulture 51(4):329-339

DOI:10.5344/ajev.2000.51.4.329

Authors:

ADP International Plant Science Consulting

Cuttings of grapevine ( Vitis vinifera L. cv. Riesling clone B 68) grafted on SO4 (Selection Oppenheim No. 4) rootstocks were grown in pots with three different soils from Franconian vineyards derived from different geological formations (namely, Loess, Muschelkalk (shell lime), or Keuper). Additionally, the influence of N-fertilizer treatment was investigated. From the midrib of leaves six to eight of the sole shoot, xylem sap was collected simultaneously by pressurizing the rhizosphere during the vegetative growth phase. The chemical composition of xylem sap was determined and compared with that of the aqueous soil extract. In Muschelkalk soil, carbon, nitrogen, and calcium were present in the greatest concentrations. Sulfur, boron, magnesium, sodium, and potassium were greatest in Keuper, and the concentrations in Loess soil were intermediate. Aqueous extraction of the soils resulted in a two-fold greater concentration of total solutes in Keuper extract compared with Muschelkalk, and more than threefold than in Loess. The apparent volume flow was greatest in the middle leaves along the shoot and in plants grown on Keuper; additionally there was a tendency for fertilizer treatment to increase flow. The concentrations of mineral ions in xylem sap were the same in all the leaves of a shoot of grapevine. An important exception was the supply to the leaves of amino acids, which increased in concentration along the transpiration stream and were greatest in the youngest leaves (particularly in non-fertilized plants). Potassium was the dominant cation in xylem sap and was greatest in plants grown on Keuper. Concentrations of sodium and calcium were increased in non-fertilized plants, but not significantly in vines grown on Muschelkalk. In xylem sap, nitrate was the major anion, followed by malate. Nitrate concentration was greatest in plants grown on Muschelkalk, while malate was greater in plants grown on Keuper. Chloride, sulfate, and phosphate concentration in sap were increased by fertilizer treatment. Abscisic acid was markedly increased in xylem sap of non-fertilized plants grown on Loess and Muschelkalk and was discussed as a signal for nutrient limitation. If Keuper was the substrate it was also increased by fertilizer treatment. Of the organic N-compounds, glutamine was the largest fraction. On the basis of the relation of nitrate to total N in xylem sap, it could be assumed that about 40% to 75% of nitrate reduction took place in the shoots. In general, soil type had only a moderate effect on the chemical composition of the xylem sap compared with the effect of N-fertilizer.

Nutrient composition of leaves and fruit juice of grapevine as affected by soil and nitrogen fertilization

Article

Aug 2009
J PLANT NUTR SOIL SC

Andreas D Peuke

Effects of soil type and nitrogen (N) fertilizer–application rates on the nutrient composition of grapevine (Vitis vinifera L. cv. Riesling) leaves during a growing cycle were compared with the composition of the resulting grape juice. Grapevines were planted in 75 L containers that had been installed in a vineyard and filled with three different vineyard soils (loess, shell lime, and Keuper). Four typical levels of N fertilizer (40, 80, 120, and 160 kg N ha–1) were applied. Elemental composition of mature leaves sampled seven times during the growing cycle as well as of the extracted grape juice was analyzed. The time of sampling affected all measured elements (C, N, Ca, K, P, Mg, S, Fe, Zn, Mn, and B) in the leaves. Nitrogen-fertilizer rate affected the concentrations of all elements except Ca and Mg, while the soil type had significant effects on elemental composition of the leaves with the exception of N, B, and Ca. Soil type had a significant effect on K, S, Mn, and B in the grape juice. Increasing rates of N fertilizer increased C concentration in the grape juice significantly and affected its elemental composition similar to the effects in leaves. This may be explained with the role of leaves as the source for supplying the grapes during ripening via phloem transport. Cluster analysis for the elemental composition of soils, leaves, and grape juice revealed no consistent relationships indicating that other soil characteristics in addition to the mineral concentration influence the elemental composition of grapevine leaves and grape juice.

NO 3 – , K + , and chlorophyll index in fertigated grapevines in the semi-arid region of Brazil

Article

Full-text available

Jan 2023

Evaluating the effects of N and K supply on grapevines ( Vitis vinifera L.) and the techniques for nutritional diagnosis is of great importance for fertigation management of this crop. This study evaluated the effects of N and K fertigation on the soluble concentrations of NO 3 – and K ⁺ in the petiole sap and on the leaf chlorophyll index in drip irrigated ‘Syrah’ grapevine (from 17 June 2013 to 25 Nov 2014). The treatments consisted of five levels of N (0, 15, 30, 60 and 120 kg ha –1 ) and K 2 O (0, 15, 30, 60 and 120 kg ha –1 ), combined in an incomplete 5 ² factorial scheme in 13 combinations and arranged in randomized blocks with four replications. We determined NO 3 – and K ⁺ concentrations in petiole sap, leaf chlorophyll index, grapevine cluster mass and number per plant, mean grapevine cluster mass, and phenolic composition. High NO 3 – concentrations contributed positively to grapevine yield; however, increased K+ concentrations caused a negative response of sap. For 120 kg N ha –1 rate, NO 3 – in the sap and chlorophyll index showed higher values at the flowering stage, while high values for K ⁺ were observed during the grape-ripening stage. Vitis vinífera L.; fertigation; petiole

Increasing photosynthetic performance and post-silking N uptake by moderate decreasing leaf source of maize under high planting density

Article

Full-text available

Feb 2021

To date, little attention has been paid to the effects of leaf source reduction on photosynthetic matter production, root function and post-silking N uptake characteristics at different planting densities. In a 2-year field experiment, Xianyu 335, a widely released hybrid in China, was planted at 60 000 plants ha–1 (conventional planting density, CD) and 90 000 plants ha–1 (high planting density, HD), respectively. Until all the filaments protruded from the ear, at which point the plants were subjected to the removal of 1/2 (T1), 1/3 (T2) and 1/4 (T3) each leaf length per plant, no leaf removal served as the control (CK). We evaluated the leaf source reduction on canopy photosynthetic matter production and N accumulation of different planting densities. Under CD, decreasing leaf source markedly decreased photosynthetic rate (Pn), effective quantum yield of photosystem II (ΦPSII) and the maximal efficiency of photosystem II photochemistry (Fv/Fm) at grain filling stage, reduced post-silking dry matter accumulation, harvest index (HI), and the yield. Compared with the CK, the 2-year average yields of T1, T2 and T3 treatments decreased by 35.4, 23.8 and 8.3%, respectively. Meanwhile, decreasing leaf source reduced the root bleeding sap intensity, the content of soluble sugar in the bleeding sap, post-silking N uptake, and N accumulation in grain. The grain N accumulation in T1, T2 and T3 decreased by 26.7, 16.5 and 12.8% compared with CK, respectively. Under HD, compared to other treatments, excising T3 markedly improved the leaf Pn, ΦPSII and Fv/Fm at late-grain filling stage, increased the post-silking dry matter accumulation, HI and the grain yield. The yield of T3 was 9.2, 35.7 and 20.1% higher than that of CK, T1 and T2 on average, respectively. The T3 treatment also increased the root bleeding sap intensity, the content of soluble sugar in the bleeding sap and post-silking N uptake and N accumulation in grain. Compared with CK, T1 and T2 treatments, the grain N accumulation in T3 increased by 13.1, 40.9 and 25.2% on average, respectively. In addition, under the same source reduction treatment, the maize yield of HD was significantly higher than that of CD. Therefore, planting density should be increased in maize production for higher grain yield. Under HD, moderate decreasing leaf source improved photosynthetic performance and increased the post-silking dry matter accumulation and HI, and thus the grain yield. In addition, the improvement of photosynthetic performance improved the root function and promoted post-silking N uptake, which led to the increase of N accumulation in grain.

Biological and functional properties of xylem sap extracted from grapevine (cv. Rosario Bianco)

Article

Oct 2020
SCI HORTIC-AMSTERDAM

Xylem sap exudes from grapevine branches and ensures survival during the dormant period. However, the extensive analysis on the biological and functional characterization of xylem sap has not yet been carried out. Therefore, to comprehend the critical role and potential usage of the xylem sap, we identified and quantified the panel of active ingredients, such as protein, amino acids, carbohydrates, saponins, flavonoids, phenolic compounds, alkaloids, and polyphenols. Results indicates that bleeding sap is slightly acidic, with the accumulation of oxalic acid, tartaric acid, malic acid, lactic acid, and citric acid. Identification and quantification of sugars depicted that xylem sap is mainly rich in fructose, glucose, and lactose. Moreover, distinct amino acids (16), hormones (9), and mineral elements are identified in the bleeding sap. These bioactive compounds are vital for vine growth and development. In addition, xylem sap also has the growth-promoting ability and can be used as a tissue culturing medium for plants. Finally, functional studies suggested that xylem sap possesses antifungal effects that can be considered as a bacteriostatic agent against Botrytis cinerea. Overall, these findings suggested that xylem sap possesses the panel of antioxidants, protein, and growth-promoting and antifungal properties.

Single-seed sowing increased pod yield at a reduced seeding rate by improving root physiological state of Arachis hypogaea

Article

Full-text available

Apr 2020

Double-seed sowing (two seeds per hole) is the dominant pattern of peanut sowing in China, but within-hole plant competition usually limits their growth and yield formation. Besides, the traditional double-seed sowing method does not facilitate mechanization during sowing. The objective of this study was to determine if single-seed sowing at a proper seeding rate yielded better than traditional double-seed sowing pattern and the differences of physiological metabolism of roots. A field experiment was conducted in two consecutive years to compare pod yields of single-seed sowing at 180 000 (S180), 225 000 (S225), and 270 000 seeds ha⁻¹ (S270) with that of double-seed sowing at 270 000 seeds ha⁻¹ (D270) using a completely randomized block design with four replications. And the root bleeding sap rate, nutrient content, and the main hormone contents in root bleeding sap were also comparatively investigated. Although the pod yields of single-seed sowing at the three densities were higher than that of traditional double-seed sowing (D270), S225 yielded better than the other two single-seed sowing treatments (S180 and S270). The increased pod yield in single-seed sowing at 225 000 seeds ha⁻¹ was mainly due to the higher pod dry weight per plant and harvest index. The improved pod dry weight and shoot growth had closely relationship with the enhanced root physiological traits such as the increased root bleeding sap rate, content of free amino acids, soluble sugars, K⁺, Mg²⁺, Zn²⁺, and Ca²⁺ of the individual plant root. The improved activity of root reductive, nitrate reductase (NR) and ATPase and higher zeatin and zeatin riboside (Z+ZR) content of root bleeding sap were also crucial to the pod and shoot growth of peanut. Single-seed sowing at a moderate seeding rate (S225) is a potential practice to increase pod yield and to save seed cost.

Contribution of soil elemental contents and Cu and Sr isotope ratios to the understanding of pedogenetic processes and mechanisms involved in the soil-to-grape transfer (Soave vineyard, Italy)

Article

Feb 2019

The Amino Acid Distribution in Rachis Xylem Sap and Phloem Exudate of Vitis vinifera ‘Cabernet Sauvignon’ Bunches

Article

Apr 2016

Amino acids are essential to grape berry and seed development and they are transferred to the reproductive structures through the phloem and xylem from various locations within the plant. The diurnal and seasonal dynamics of xylem and phloem amino acid composition in the leaf petiole and bunch rachis of field-grown Cabernet Sauvignon are described to better understand the critical periods for amino acid import into the berry. Xylem sap was extracted by the centrifugation of excised leaf petioles and rachises, while phloem exudate was collected by immersing these structures in an ethylenediaminetetraacetic acid (EDTA) buffer. Glutamine and glutamic acid were the predominant amino acids in the xylem sap of both grapevine rachises and petioles, while arginine and glycine were the principal amino acids of the phloem exudate. The amino acid concentrations within the xylem sap and phloem exudate derived from these structures were greatest during anthesis and fruit set, and a second peak occurred within the rachis phloem at the onset of ripening. The concentrations of the amino acids within the phloem and xylem sap of the rachis were highest just prior to or after midnight while the flow of sugar through the rachis phloem was greatest during the early afternoon. Sugar exudation rates from the rachis was greater than that of the petiole phloem between anthesis and berry maturity. In summary, amino acid and sugar delivery through the vasculature to grape berries fluctuates over the course of the day as well as through the season and is not necessarily related to levels near the source.

Effects of different mineral nutrients on abscisic acid in maize (Zea mays)

Article

Full-text available

Jan 2003

The effects of different concentrations of various macroelements on growth and endogenous ABA (absisic acid) levels in root, stem, leaf and flower tissue of maize (Zea mays) were studied. Plants were cultivated in sand and supplied twice a week with a nutrient solution containing optimum, excessive or deficient concentrations of nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and iron. Plants were harvested at three different stages: vegetative (4-5 leaves), flowering, and fruiting. Fresh weight, leaf and stem size, leaf number and ABA concentrations differed remarkably between plants cultured in abnormal concentrations of macroelements compared to the controls. In general, deprivation of macroelements caused an increase in ABA levels. Deficiency of N, P, K, S and Fe in the nutrient solution resulted in marked increases in the levels of ABA extracted from root, leaf, stem and flower at the three developmental stages. Excessive concentrations of these macroelements resulted in a decrease in ABA levels in all parts of plants at all three stages as compared with their respective controls. ABA levels in roots, stems, and leaves were elevated from 3% to 159% in N, P, K, and S limited plants whereas the levels of ABA in these same organs were reduced from 1% to 98% in the presence of excessive levels of N, K, P and S.

Experimental Evidence for Diel Δ(15) n-Patterns in Different Tissues, Xylem and Phloem Saps of Castor Bean (Ricinus Communis L.).

Article

May 2013
PLANT CELL ENVIRON

Nitrogen isotope signatures in plants might give insights in the metabolism and allocation of nitrogen. To obtain a deeper understanding of the modifications of the nitrogen isotope signatures, we determined δ(15) N in transport saps and in different fractions of leaves, axis and roots during a diel course along the plant axis. The most significant diel variations were observed in xylem and phloem saps where δ(15) N was significantly higher during day compared to the night. However, in xylem saps this was observed only in the canopy but not at the hypocotyl positions. In the canopy δ(15) N was correlated fairly well between phloem and xylem saps. These variations in δ(15) N in transport saps can be attributed to nitrate reduction in leaves during the photoperiod as well as to (15) N enriched glutamine acting as transport form of N. δ(15) N of the water soluble fraction of roots and leaves partially affected δ(15) N of phloem and xylems saps. δ(15) N patterns are likely the result of a complex set of interactions and N-fluxes between plant organs. Furthermore, the natural nitrogen isotope abundance in plant tissue is not constant during the diel course - a fact that needs to be taken into account when sampling for isotopic studies.

Review of potassium nutrition in grapevines with special emphasis on berry accumulation

Article

Full-text available

Mar 2008
AUST J GRAPE WINE R

Potassium (K) is essential for vine growth and yield. Grape berries are a strong sink for K, particularly during ripening. Excess K levels in grape berries may have a negative impact on wine quality, mainly because it decreases free tartaric acid resulting in an increase in the pH of grape juice, must and wine. In Australia, high K status is common in most vineyards, which reflects the high K and high pH values of most Australian grape juice. This necessitates pH adjustment during the vinification process, and tartaric acid addition is a common practice in most Australian wineries. High K concentration may also lead to excessive loss of the additional tartaric acid by precipitation as potassium bitartrate and, as a consequence, pH adjustment becomes more difficult and expensive. Ensuring naturally low K levels in the berry will help reduce costs of input and waste management at the winery. Potential vineyard management options to manipulate berry K accumulation include selective use of rootstock/scion combination, canopy management and irrigation strategies. However, the impact of these practices on determining the optimum K concentration requires careful calibration of production parameters and the desirable grape juice and wine quality in relation to tissue K concentration. This paper reviews and discusses the possible functions of K in grape berries, translocation of K into the berry, and genetic and cultural factors that may affect the accumulation of K in the berry. This will help to identify the key research and management strategies needed for controlling K concentrations in grape berries.

Biomass distribution and nitrate assimilation in response to N supply for Vitis vinifera L. cv. Cabernet Sauvignon on five Vitis rootstock genotypes

Article

Mar 2008
AUST J GRAPE WINE R

Effects of nitrogen (N) supply on biomass distribution as well as N effects on NO3“assimilation, were examined in two-year-old graftlings of Vitis vinifera L. cv. Cabernet Sauvignon on five rootstocks. Whole-plant biomass in all graftlings more than doubled with increased N supply in solution from 0.25 to 8 mM. Whole plant biomass was also affected by rootstock genotype, but to a lesser extent than by N supply. Biomass allocation to roots declined with increased N supply for all stock-scion combinations, but the magnitude of that response varied with rootstock genotype. Nitrate reductase activity (NRA) in leaves increased with increased N supply for all stock-scion combinations, whereas root NRA increased only up to 1 mM N supply, dropping markedly with additional N. NRA in leaves was one to two orders of magnitude higher than NRA in roots - a difference that increased steadily with increased N supply. By implication, grapevine leaves have a much higher capacity for NO3-- reduction than do grapevine roots, and any contribution by roots to whole-vine NO3-- assimilation declines even further as NO3-- availability increases.

Experiments to modify grape juice potassium content and wine quality on granite derived soils near Paardenberg

Article

G. Agenbach

High potassium content in grape juice and wine are associated with low quality red wine in warm wine producing countries. In an attempt to reduce the potassium content of juice, must and wine, a field experiment was laid out on the farms Meerlus and Kersfontein in the Paardeberg area near Wellington in 1998 on granite derived soils to investigate the effect of canopy management and fertiliser applications on berry K accumulation and wine quality. Four fertiliser applications, three canopy treatments and a MgSO4 foliar spray were studied. The three fertiliser treatments being: none (control), CaSO4, Ca(OH)2, and MgSO4 applications. The canopy treatments were: thin to two shoots per bearer, tip, vertical shoot positioning (VSP) and the removal of yellow leaves and lateral shoots (canopy 1), thin to three shoots per bearer, top after véraison and VSP (canopy 2) and VSP with top after véraison (canopy 3/control). Magnesium sulfate sprays were applied at véraison for two seasons (1999/00 and 2000/01). Seasonal effects produced the most significant differences in this experiment. Canopy treatments did not affect juice K concentration at harvest. Canopy 1 and 2 produced significantly lower wine pH values at Kersfontein. Fertiliser treatments had no effect on juice K concentration nor did it affect wine quality. Magnesium sulphate foliar sprays did not affect juice K concentration at harvest but significantly lowered juice and wine pH, improved wine colour density and total phenolic content. It appears for this experiment that soil K content before véraison, shoot growth at and after véraison and water stress after véraison were the main factors determining juice K concentration at harvest. Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2006.

Insights into the Uptake, Distribution, and Metabolism of 3-Isobutyl-2-hydroxypyrazine in Grapevine Using a Stable Isotope Tracer

Article

Apr 2023
J AGR FOOD CHEM

Methoxypyrazines (MPs) are potent aroma compounds that have been predominately studied in grape berries but can also be detected in other vine tissues. The synthesis of MPs in berries from hydroxypyrazines by VvOMT3 is well established, but the origin of MPs in vine tissues that have negligible VvOMT3 gene expression is unknown. This research gap was addressed through the application of stable isotope tracer 3-isobutyl-2-hydroxy-[2H2]-pyrazine (d2-IBHP) to the roots of Pinot Meunier L1 microvines and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) quantification of HPs from grapevine tissues following a novel solid-phase extraction method. Four weeks post-application, d2-IBHP and its O-methylated product 3-isobutyl-2-methoxy-[2H2]-pyrazine (d2-IBMP) were present in excised cane, berry, leaf, root, and rachis material. Translocation of d2-IBHP and d2-IBMP was investigated, but results were inconclusive. Nonetheless, knowledge that d2-IBHP, and potentially d2-IBMP, are translocated from roots to other vine organs, including the berries, could provide opportunities for controlling MP accumulation in grapevine tissues pertinent to winemaking.

Effects of Carbon-Based Fertilizer on Maize Root Morphology, Root Bleeding Rate and Components in Northeast China

Article

Full-text available

Mar 2023

Maize (Zea mays L.) is the largest grain crop in Heilongjiang Province. Carbon-based fertilizer is a mixed fertilizer produced by adding a certain proportion of chemical fertilizer with biochar as the loading substrate. In this study, the effects of carbon-based fertilizer on the rhizosphere soil microenvironment and maize root system were discussed. Two maize varieties, Xianyu 335 and Jingke 968, were selected and six treatments were set as follows, including no fertilization (CK1), conventional fertilizer (CK2) and the amount of carbon-based fertilizer, which were 3 t/hm2, 3.75 t/hm2, 4.5 t/hm2 and 5.25 t/hm2, respectively. The results showed that carbon-based fertilizer increased the total root length, root volume, root area and root tip number of maize, and the root length, root volume, root area and root tip number of 4.5 t treatment performed better at all stages, which was significantly higher than that of chemical fertilizer. On 16 August (early filling stage), most of the root color changed from milky white to dark brown, the root clarity decreased, the number of roots decreased, the root volume significantly decreased and the root began to age, while the number and volume of roots treated with the carbon-based fertilizer remained stable, the root color was milky white, the morphological structure was clear and there was basically no aging. The carbon-based fertilizer treatment significantly increased the root biomass of 0–15 cm above the plant, 15–30 cm and 30–45 cm between the plants and 0–15 cm between the ridges, forming a wide and deep high-yield root system. The carbon-based fertilizer significantly increased the bleeding rate. On 8 July (jointing stage), Xianyu 335 and Jingke 968 reached the maximum value at the 3 t and 3.75 t treatments, respectively. The carbon-based fertilizer treatment had no significant effect on the amino acid content, but significantly increased the amino acid transport rate on 8 July (jointing stage) and 16 August (early filling stage). The transport rate of inorganic phosphorus gradually decreased with the advancement of the growth process. On 8 July (jointing stage), the ammonium nitrogen content and transport rate of the two varieties reached the maximum value at the treatment of 4.5 t and 3.75 t, which was significantly higher than the treatment of chemical fertilizer and no fertilizer, and showed a gradual downward trend with the advancement of the growth process. The soluble sugar content was relatively low in the early stage and increased rapidly on 4 September (waxy ripening stage). Both varieties reached the maximum value at 4.5 t treatment, and the transport rate reached the maximum value at 3.75 t treatment, which was significantly higher than that of the chemical fertilizer treatment. In conclusion, the carbon-based fertilizer significantly increased the yield of maize, and the yield of maize under the 4.5 t treatment reached the maximum, which was 15.02% and 18.24% higher than that of the chemical fertilizer treatment, respectively.

Exogenous Spermidine Optimizes Nitrogen Metabolism and Improves Maize Yield under Drought Stress Conditions

Article

Full-text available

Aug 2022

This study was to explore the nitrogen metabolism and transcriptome mechanism of spermidine (Spd) under drought stress conditions. Firstly, maize variety Xianyu 335 (drought insensitive type) and Fenghe 1 (drought sensitive type) were chosen as experimental materials under hydroponic conditions. The effects of PEG-6000 combined with Spd application on nitrogen metabolism were studied. Secondly, we chose maize variety Xianyu 335 for the field experiment. At the flowering stage, normal water treatment and moderate drought stress were carried out, respectively. The results showed that: (1) Hydroponics experiment showed that the content of NH4+ in the leaves of maize seedlings under drought stress increased significantly, while the content of NO3− and nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamine dehydrogenase (GDH), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) increased significantly. Spd can promote the assimilation of excess ammonia by enhancing the activities of ammonia assimilating enzymes GS/GOGAT and GDH, and transaminase (GOT and GPT), effectively alleviate the ammonia toxicity and nitrogen metabolism disorder induced by drought stress. (2) Pot experiment showed that Spd significantly promoted the root growth of maize under drought stress, so as to improve the absorption and utilization of water and nutrients. In addition, Spd can improve the chlorophyll content and photosynthetic rate of maize leaves under drought stress. After the application of exogenous Spd, the photosynthetic green leaf area increased, the leaf senescence rate slowed down, and the dry matter accumulation increased after anthesis, resulting in the increase of grain weight and grain number per ear, and finally improve the maize yield.

Conservation tillage and nutrient management practices in summer rice (Oryza sativa L.) favoured root growth and phenotypic plasticity of succeeding winter pea (Pisum sativumL.) under eastern Himalayas, India

Article

Full-text available

May 2021

Low soil moisture during dry season, poor soil properties and lack of adequate crop varieties are the major constraints for sustainable intensification of eastern Himalayas in changing climate. Suitable varieties, tillage alteration and integrated nutrient management with emphasis on locally available crop residues/plant biomass may help addressing these issues. The role of minimum tillage (MT) and no-till (NT), and organic matter substitution on conferring of favourable root environment, improvement in morpho-physiology and subsequent productivity of the crops are not objectively studied in Himalayan ecosystems. Thus, a six year field study was conducted for examining the residual effect of tillage and nutrient management (NM) practices applied to summer (rainy) rice (Oryza sativa L) on root growth-attributes and impact on morpho-physiology of succeeding winter pea (Pisums ativum L.) grown uniformly under NT. Higher root surface area, total root length, root volume, root length ratio (RLR) and root tissue densityin pea crop were observed under residual effect of conventional tillage (CT) relative to NT and MT. In addition, significantly higher values of functional root traits viz., root length ratio (RLR), root mass ratio and root finenessin pea were observed under CT and application of 50% NPK and 100% NPK relative to other tillage and NM practices. However, increased root exudation was observed under NT and MTalong with organic residue addition. Noticeable changes in stress responsive morpho-physiological traits like enhanced chlorophyll pigmentation and favourable leaf characteristics were observed in pea crop grown under NT with 50% NPK+weed biomass (WB)/green leaf manure (GLM) applications. Higher leaf area expansion and thickness were recorded with optimum turgidity under NT and MT than that under CT. Comparative increase in green pod and stover yield of pea with enhanced partition efficiency and harvest index were recorded under MT/NT along with 50% NPK+WB/GLM application than that under CT and other NM practices. Thus, adoption of MT/NT along with 50% NPK+WB/GLM in summer rice is recommended for inducing favourable root environment and optimised pea production in succeeding winter season in study region of the Eastern Himalayas, India and other similar agro-ecosystems.

Grapevine phenolic compounds influence cell surface adhesion of Xylella fastidiosa and bind to lipopolysaccharide

Article

Full-text available

Oct 2020
PLOS ONE

Bacterial phytopathogen Xylella fastidiosa specifically colonizes the plant vascular tissue through a complex process of cell adhesion, biofilm formation, and dispersive movement. Adaptation to the chemical environment of the xylem is essential for bacterial growth and progression of infection. Grapevine xylem sap contains a range of plant secondary metabolites such as phenolics, which fluctuate in response to pathogen infection and plant physiological state. Phenolic compounds are often involved in host-pathogen interactions and influence infection dynamics through signaling activity, antimicrobial properties, and alteration of bacterial phenotypes. The effect of biologically relevant concentrations of phenolic compounds coumaric acid, gallic acid, epicatechin, and resveratrol on growth of X. fastidiosa was assessed in vitro. None of these compounds inhibited bacterial growth, but epicatechin and gallic acid reduced cell-surface adhesion. Cell-cell aggregation decreased with resveratrol treatment, but the other phenolic compounds tested had minimal effect on aggregation. Expression of attachment (xadA) and aggregation (fimA) related genes were altered by presence of the phenolic compounds, consistent with observed phenotypes. All four of the phenolic compounds bound to purified X. fastidiosa lipopolysaccharide (LPS), a major cell-surface component. Information regarding the impact of chemical environment on pathogen colonization in plants is important for understanding the infection process and factors associated with host susceptibility.

The effects of fall fertilization on the growth of Chinese pine and Prince Rupprecht’s larch seedlings

Article

Full-text available

Oct 2019

Nutrient loading in the fall is a practical way to improve seedling quality and has been proven to increase nutrient accumulation, translocation and utilization. Few studies have reported on the variation in free amino acids as a result of fall fertilization, especially for different seasonal needle habits (evergreen, deciduous). Therefore, a balanced two-factor factorial design with one fall fertilization treatment (10 mg N/seedling) and Chinese pine (Pinus tabulaeformis Carr.) and Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr.) seedlings was used to examine growth response over one nursery season. Associated changes between fall fertilization, N storage and free amino acids were analyzed. Results showed that: (1) stem height, diameter and biomass for both species were similar between controls and fall fertilization treatments; (2) compared to controls, fall fertilization increased Chinese pine needle and root N by 17.7% and 36.9%, respectively. For Prince Rupprecht’s larch, fall fertilization resulted in 26.3% and 34.54% more N in stem and roots, respectively, than controls; (3) the three main amino acids in control and fertilization treatments in Prince Rupprecht’s larch seedlings were glutamine, arginine and proline, and in Chinese pine seedlings were glutamine, arginine and γ-amino butyric acid; (4) total amino acid contents were not significantly increased by fall fertilization, but glutamine in Chinese pine and Prince Rupprecht’s larch increased by 64.2% and 35.2%, respectively. Aboveground biomass of Prince Rupprecht’s larch had higher proline contents than Chinese pine, which suggests that the stress resistance of the aboveground tissue may be higher for Prince Rupprecht’s larch. The results indicate that different plant organs with various response are well adapted to nitrogen loading for nutrient storage in evergreen and deciduous conifer seedlings.

Temporal Dynamics of the Sap Microbiome of Grapevine Under High Pierce’s Disease Pressure

Article

Full-text available

Oct 2019

Grapevine is a pillar of the California state economy and agricultural identity. This study provides a comprehensive culture-independent microbiome analysis from the sap of grapevine overtime and in a context of a vascular disease. The vascular system plays a key role by transporting nutrient, water and signals throughout the plant. The negative pressure in the xylem conduits, and low oxygen and nutrient content of its sap make it a unique and underexplored microbial environment. We hypothesized that grapevine hosts in its sap, microbes that have a beneficial impact on plant health by protecting against pathogen attack and supporting key biological processes. To address this hypothesis, we chose a vineyard under high Pierce’s disease (PD). PD is caused by the xylem-dwelling pathogenic bacterium Xylella fastidiosa. We selected ten grapevines within this vineyard with a range of disease phenotypes, and monitored them over 2 growing seasons. We sampled each vines at key phenological stages (bloom, veraison, and post-harvest) and used an amplicon metagenomics approach to profile the bacterial (16S -V4) and fungal (ITS) communities of the sap. We identified a core microbiome of the sap composed of seven bacterial (Streptococcus, Micrococcus, Pseudomonas, Bacteroides, Massilia, Acinetobacter and Bacillus) and five fungal (Cladosporium, Mycosphaerella, Alternaria, Aureobasidium, and Filobasidium) taxa that were present throughout the growing season. Overall, the sap microbial makeup collected from canes was more similar to the root microbial profile. Alpha diversity metrics indicated a microbial enrichment at bloom and in vines with moderate PD severity suggesting a host-driven microbial response to environmental cues. Beta diversity metrics demonstrated that disease condition and plant phenology impacted microbial community profiles. Our study identified several potential taxonomic targets with antimicrobial and plant growth promoting capabilities that inhabit the grapevine sap and that should be further tested as potential biological control or biofertilizer agents.

Dynamiques saisonnières des réserves carbonées et azotées chez le chêne sessile (Quercus petraea) et le hêtre (Fagus sylvatica) adultes

Thesis

Jan 2011

Rana el Zein

Le chêne sessile et le hêtre sont deux espèces feuillues décidues tempérées, caractérisées par des phénologies foliaires et cambiales contrastées. Afin de progresser dans la compréhension de la gestion des réserves qui sont des composantes importantes des cycles internes du carbone et de l'azote, nous avons étudié la dynamique saisonnière des réserves carbonées (C) et azotées (N) chez des arbres adultes des deux espèces dans leur environnement naturel. Afin de répondre à nos objectifs, nous avons développé une approche pluridisciplinaire associant écophysiologie, biochimie et isotopie. Le suivi mensuel des variations saisonnières des réserves C et N dans le tronc a révélé chez le chêne une forte remobilisation de l'amidon à partir des cernes les plus récents au printemps pour fournir le carbone nécessaire pour la croissance du bois initial du nouveau cerne qui est concomitante à l'expansion foliaire. Chez le hêtre, la croissance printanière ne semble pas dépendante des réserves C du tronc. Chez les deux espèces, deux polypeptides de 13 et de 26 kDa s'accumulent avec la sénescence foliaire en automne, sont très abondants en période hivernale froide et sont remobilisés avec le débourrement au printemps. Cette cinétique saisonnière leur confère un rôle dans le stockage de l'azote (protéines végétatives de réserve, VSP), mais n'exclut pas un rôle dans la tolérance au froid. Chez le chêne sessile, l'étude de la source d'azote pour la croissance des feuilles et des pousses par marquage isotopique au 15N a montré que les réserves N contribuent jusqu'à 90% de l'azote total des nouveaux organes aux premiers stades de développement. La contribution de l'azote nouvellement assimilé ne devient significative que quand le débourrement est achevé. L'étude de la répartition et des quantités des composés C et N non-structuraux à l'échelle de l'arbre a été réalisée par un échantillonnage destructif d'arbres des deux espèces en hiver (Janvier) et à l'étalement complet des feuilles (Juin). Cette étude a montré i) une distribution des concentrations entre organes dépendante de leur fonction physiologique, de l'anatomie du bois et de la distance aux organes puits, ii) l'importance du tronc et des racines dans le stockage des réserves en hiver, iii) l'importance des quantités d'azote non-structural des feuilles et des pousses malgré leur faible biomasse, iv) des quantités de C et N non-structuraux plus importants chez le chêne par rapport au hêtre, pouvant refléter des besoins contrastés pour la croissance et l'entretien des tissus en hiver

Metabolomic Study of Chardonnay Grapevines Double Stressed with Esca-Associated Fungi and Drought

Article

Jun 2017
PHYTOPATHOLOGY

Esca is a complex grapevine trunk disease associated with fungal infection of the xylem. However, the inconstancy of external symptoms and the ability of esca-associated fungi to inhabit grapevines without causing apparent disease, suggests that abiotic factors might be involved in the disease. Water stress has been proposed to be one of the factors influencing esca symptom manifestation, but the specific role played by water stress on esca development is unknown. We conducted a 1H-NMR spectroscopy-based metabolomic study aiming at unveiling drought-induced modifications in xylem sap composition that could contribute to esca-related infection progression. Vitis vinifera cv. Chardonnay plants were inoculated with Phaeomoniella chlamydospora or Phaeoacremonium minimum and exposed to water stress. Using this approach, 28 metabolites were identified in xylem sap. The results show water stress induces a concentration increase of most metabolites in xylem sap. Average increase above 100% was found for asparagine, isoleucine, leucine, methionine, phenylalanine, proline, tyrosine, valine, sarcosine and trigonelline. The increase of these compounds seems to be also modulated by fungal infection. This study offers further support to the putative role of drought in esca expression, and opens new avenues of research by extending the current knowledge about metabolites possibly involved in esca disease.

Characterization and expression of cytokinin signalling genes in sulfur deficient grapevine (Vitis vinifera L.)

Article

Jan 2009

João Carlos Martins Fernandes

Effects of root restriction on nitrogen and gene expression levels in nitrogen metabolism in Jumeigui grapevines (Vitis vinifera L.×Vitis labrusca L.)

Article

Full-text available

Jan 2015

To decipher the relationship between the inhibited shoot growth and expression pattern of key enzymes in nitrogen metabolism under root restriction, the effects of root restriction on diurnal variation of expression of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS1-1, GS1-2, GS2) and glutamate synthase (Fd-GOGAT, NADH-GOGAT) genes and nitrogen levels were evaluated in two-year-old Jumeigui grapevines (Vitis vinifera L.×Vitis labrusca L.) when significant differences in shoot growth were observed between treatments at expansion stage (22 days after anthesis). Grapevines were planted in root-restricting pits as root restriction and in an unrestricted field as the control. Results showed that root restriction significantly reduced shoot growth, but promoted the growth of white roots and fibrous brown roots and improved the fruit quality. (NO3−+NO2−)-N concentration in all plant parts, NH4+-N concentration in white roots and total N concentration in leaves and brown roots were significantly reduced under root restriction. Gene expression analysis revealed that mRNA levels of genes related to the GS1/NADH-GOGAT pathway were lower in root-restricted than in control petioles, whereas genes involved in the GS2/Fd-GOGAT pathway were up-regulated under root restriction. Root restriction also resulted in down-regulation of genes involved in nitrogen metabolism in leaves, especially at 10:00, while transcript levels of all these genes were enhanced in root-restricted white and brown roots at most time points. This organ-dependent response contributed to the alteration in NO3− reduction and NH4+ assimilation under root restriction, leading to less NO3− transported from roots and then assimilated in root-restricted leaves. Therefore, this study implied that shoot growth inhibition in grapevines under root restriction is closely associated with down-regulation of gene expression in nitrogen metabolism in leaves.

N and K translocation in the xylem sap of Ligustrum ovalifolium L. during spring growth

Article

Full-text available

Jan 2005

Stored organic and mineral nutrients are essential for the spring growth of ligneous woody plants. The nitrogen (N) and potassium (K) dynamics were studied on Ligustrum ovalifolium grown in container for two years (2000 and 2001) with or without fertilizer application during the second spring. Allocation of nutrient elements towards new shoots was determined. Nutrient transport in the xylem sap was qualified and quantified by a mathematical coupling between sap flow velocity and sap composition. Sap nutrient concentrations increased after bud break, corresponding to an accumulation of mobilized elements before their use for shoot growth. Glutamine and K were identified as the main compounds translocated in the xylem sap and are a consequence of both mobilization and uptake by roots of fertilised plants. They were mobilized from storage throughout spring although uptake by roots started just after the beginning of shoot growth. In plants not applied with fertilizers, N amounts in shoots were close to that of total N which circulated in xylem sap. On the other hand, total N and K circulating in the xylem sap of plants supplied with fertilizer, and K of plants not supplied with fertilizer, were higher than the amounts accumulated in shoots. The differences were attributed to the nutrient replenishment of perennial organs and to the internal N and K recirculating between shoots and roots. The roles of the internal N and K recirculating are discussed.

Tillage practices affect biomass and grain yield through regulating root growth, root-bleeding sap and nutrients uptake in summer maize

Article

Feb 2014
FIELD CROP RES

Members of the NPF3 Transporter Subfamily Encode Pathogen-Inducible Nitrate/Nitrite Transporters in Grapevine and Arabidopsis

Article

Full-text available

Nov 2013
PLANT CELL PHYSIOL

Vitis vinifera, the major grapevine species cultivated for wine production, is very susceptible to Erysiphe necator, the causal agent of powdery mildew (PM). This obligate biotrophic fungal pathogen attacks both leaf and berry, greatly affecting yield and quality. To investigate possible mechanisms of nutrient acquisition by successful biotrophs, we characterized a candidate NITRATE TRANSPORTER1/PEPTIDE TRANSPORTER FAMILY (NPF, formerly NRT1/PTR) member, grapevine NFP3.2, that was up-regulated in E. necator-inoculated susceptible V. vinifera Cabernet Sauvignon leaves, but not in resistant V. aestivalis Norton. Expression in Xenopus laevis oocytes and two-electrode voltage clamp measurements showed that VvNPF3.2 is a low-affinity transporter for both nitrate and nitrite and displays characteristics of NPF members from other plants. We also cloned the Arabidopsis ortholog, AtNPF3.1, and showed that AtNPF3.1 similarly transported nitrate and nitrite with low affinity. With an Arabidopsis triple mutant that is susceptible to E. necator, we found that AtNPF3.1 is up-regulated in the leaves of infected Arabidopsis similarly to VvNPF3.2 in susceptible grapevine leaves. Expression of the reporter β-glucuronidase (GUS) driven by the promoter of VvNPF3.2 or AtNPF3.1 in Arabidopsis indicated that both transporters are expressed in vascular tissue, with expression in major and minor veins, respectively. Interestingly, the promoter of VvNPF3.2 allowed induced expression of GUS in minor veins in PM-infected leaves. Our experiments lay the groundwork for investigating the manipulation of host nutrient distribution by biotrophic pathogens and characterizing physiological variables in the pathogenesis of this difficult to study grapevine disease.

Grapevine & Sulfur: Old Partners, New Achievements

Article

Full-text available

Jan 2009

The central role of sulfur in biological functions Sulfur (S) is the 14th more abundant element on earth crust (Charlson et al. 1992), the 9th and least abundant essential macronutrient in plants (Saito 2004) and the 6th element in the cytoplasm (Xavier and LeGall 2007). The interconversion of oxidized and reduced sulfur states, the biogeochemical sulfur cycle, depends mainly on microorganisms (Falkowski et al. 2008) and plants. The inorganic forms of S in soil consist mainly of sulfates (SO4 2-) (Mengel and Kirkby 1982).

UNDERSTANDING XYLELLA FASTIDIOSA COLONIZATION AND COMMUNICATION IN XYLEM LUMINA Project Leaders

Article

Full-text available

Flow cells that emulate xylem vessels have been microfabricated in silicon and in polydimethylsiloxane. Xylella cells in these artificial vessels are being studied for colonization and biofilm development.

Heavy traffic in the fast lane: long-distance signalling by macromolecules

Article

Full-text available

Feb 2013
NEW PHYTOL

The two major vascular conduits in plants, the xylem and phloem, theoretically provide opportunities for the long‐distance translocation of almost any type of water‐borne molecule. This review focuses on the signalling functions conveyed by the movement of macromolecules. Here, a signal is defined as the communication of information from source to destination, where it modifies development, physiology or defence through altered gene expression or by direct influences on other cellular processes. Xylem and phloem sap both contain diverse classes of proteins; in addition, phloem contains many full‐length and small RNA species. Only a few of these mobile molecules have proven functions in signalling. The transduction of signals typically depends on connection to appropriate signalling pathways. Incoming protein signals require specific detection systems, generally via receptors. Mobile RNA s require either the translation or presence of a homologous target. Given that phloem sieve elements are enucleate and lack translation machinery, RNA function requires subsequent unloading at least into adjacent companion cells. The binding of RNA by proteins in ribonucleoprotein complexes enables the translocation of some signals, with evidence for both sequence‐specific and size‐specific binding. Several examples of long‐distance macromolecular signalling are highlighted, including the FT protein signal which regulates flowering time and other developmental switches. Contents Summary 33 I. Introduction – plant communication systems 33 II. The importance of method selection and experimental design 34 III. Macromolecules in xylem and phloem 37 IV. Plasmodesmata – complex intercellular exchange junctions enabling short‐ and long‐range signalling 39 V. Phloem signalling: regulation 40 VI. Phloem signalling: specific examples 43 VII. Conclusions and prospects 45 Acknowledgements 46 References 46

Nitrogen nutrition of poplar trees

Article

Mar 2010
PLANT BIOLOGY

Many forest ecosystems have evolved at sites with growth-limiting nitrogen (N) availability, low N input from external sources and high ecosystem internal cycling of N. By contrast, many poplar species are frequent constituents of floodplain forests where they are exposed to a significant ecosystem external supply of N, mainly nitrate, in the moving water table. Therefore, nitrate is much more important for N nutrition of these poplar species than for many other tree species. We summarise current knowledge of nitrate uptake and its regulation by tree internal signals, as well as acquisition of ammonium and organic N from the soil. Unlike herbaceous plants, N nutrition of trees is sustained by seasonal, tree internal cycling. Recent advances in the understanding of seasonal storage and mobilisation in poplar bark and regulation of these processes by temperature and daylength are addressed. To explore consequences of global climate change on N nutrition of poplar trees, responses of N uptake and metabolism to increased atmospheric CO(2) and O(3) concentrations, increased air and soil temperatures, drought and salt stress are highlighted.

Cellular and subcellular localisation of glutamine synthetase and glutamate dehydrogenase in grapes gives new insights on the regulation of carbon and nitrogen metabolism

Article

Full-text available

Jan 2003

The subcellular localisation of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in grapevine (Vitis vinifera L.) leaves and flowers was investigated using immunogold-labelling experiments. In mature leaf tissue or fully developed flowers, GS was visualised both in the cytosol and in the chloroplasts, a high proportion of the protein being present in the phloem companion cells. GDH was preferentially located in the mitochondria of the phloem companion cells in both leaves and flowers. This observation suggests that, in conjunction with GS, GDH plays a major role in controlling the translocation of organic carbon and nitrogen metabolites in both vegetative and reproductive organs. Significant amounts of GDH protein were also visualised in multivesicular bodies within the flower receptacle. Although the function of such organelles is still unknown, its is possible that the presence of GDH in such cellular structures is important for the recycling of carbon and nitrogen molecules in senescing tissues in which the enzyme is generally induced.

Upstream Migration of Xylella fastidiosa via Pilus-Driven Twitching Motility

Article

Full-text available

Jan 2005
J BACTERIOL

Xylella fastidiosa is a xylem-limited nonflagellated bacterium that causes economically important diseases of plants by developing biofilms that block xylem sap flow. How the bacterium is translocated downward in the host plant's vascular system against the direction of the transpiration stream has long been a puzzling phenomenon. Using microfabricated chambers designed to mimic some of the features of xylem vessels, we discovered that X. fastidiosa migrates via type IV-pilus-mediated twitching motility at speeds up to 5 μm min−1 against a rapidly flowing medium (20,000 μm min−1). Electron microscopy revealed that there are two length classes of pili, long type IV pili (1.0 to 5.8 μm) and short type I pili (0.4 to 1.0 μm). We further demonstrated that two knockout mutants (pilB and pilQ mutants) that are deficient in type IV pili do not twitch and are inhibited from colonizing upstream vascular regions in planta. In addition, mutants with insertions in pilB or pilQ (possessing type I pili only) express enhanced biofilm formation, whereas a mutant with an insertion in fimA (possessing only type IV pili) is biofilm deficient.

Oxygen isotope enrichment of organic matter in Ricinus communis during the diel course and as affected by assimilate transport

Article

Feb 2007

The oxygen isotope composition in leaf water and organic compounds in different plant tissues is useful for assessing the physiological performance of plants in their environment, but more information is needed on Delta(18)O variation during a diel course. Here, we assessed Delta(18)O of the organic matter in leaves, phloem and xylem in stem segments, and fine roots of Ricinus communis during a full diel cycle. Enrichment of newly assimilated organic matter in equilibrium with leaf water was calculated by applying a nonsteady-state evaporative enrichment model. During the light period, Delta(18)O of the water soluble organic matter pool in leaves and phloem could be explained by a 27 per thousand enrichment compared with leaf water enrichment. Leaf water enrichment influenced Delta(18)O of phloem organic matter during the night via daytime starch synthesis and night-time starch remobilization. Phloem transport did not affect Delta(18)O of phloem organic matter. Diel variation in Delta(18)O in organic matter pools can be modeled, and oxygen isotopic information is not biased during transport through the plant. These findings will aid field studies that characterize environmental influences on plant water balance using Delta(18)O in phloem organic matter or tree rings.

Long-term excessive nitrogen application decreases spring maize nitrogen use efficiency via suppressing root physiological characteristics

Article

May 2024

Understanding physiological mechanisms of variation in grain filling of maize under high planting density and varying nitrogen applicate rate

Article

Full-text available

Aug 2022

Grain filling is a critical process for achieving a high grain yield in maize (Zea mays L.), which can be improved by optimal combination with genotype and nitrogen (N) fertilization. However, the physiological processes of variation in grain filling in hybrids and the underlying mechanisms of carbon (C) and N translocation, particularly under various N fertilizations, remain poorly understood. The field experiment was conducted at Gongzhuling Farm in Jilin, China. In this study, two maize hybrids, i.e., Xianyu 335 (XY335) and Zhengdan958 (ZD958) were grown with N inputs of 0, 150, and 300 kg N ha–1 (N0, N150, and N300) in 2015 and 2016. Results showed that the N application significantly optimized grain-filling parameters for both maize hybrids. In particular, there was an increase in the maximum filling rate (Gmax) and the mean grain-filling rate (Gmean) in XY335 by 8.1 and 7.1% compared to ZD958 under the N300 kg ha–1 (N300) condition, respectively. Simultaneously, N300 increased the small and big vascular bundles area of phloem, and the number of small vascular bundles in peduncle and cob at the milking stage for XY335. XY335 had higher root bleeding sap (10.4%) and matter transport efficiency (8.4%) of maize under N300 conditions, which greatly enhanced the ¹³C assimilates and higher C and N in grains to facilitate grain filling compared to ZD958. As a result, the grain yield and the sink capacity for XY335 significantly increased by 6.9 and 6.4% compared to ZD958 under N300 conditions. These findings might provide physiological information on appropriate agronomy practices in enhancing the grain-filling rate and grain yield for maize under different N applications, namely the optimization variety and N condition noticeably increased grain filling rate after silking by improving ear vascular structure, matter transport efficiency, and enhancing C and N assimilation translocation to grain, eventually a distinct improvement in the grain sink and the grain yield.

Exogenous Hemin Optimized Maize Leaf Photosynthesis, Root Development, Grain Filling, and Resource Utilization on Alleviating Cadmium Stress Under Field Condition

Article

Nov 2021

The purpose of this study was to analyze the response and mitigation mechanism of hemin to maize under cadmium stress. Maize variety Xianyu 335 was exposed to cadmium stress (100 mg kg−1) and was sprayed different concentrations of hemin (150, 250, and 300 μmol L−1) at the flowering stage. The photosynthetic characteristics, leaf senescence characteristics, root activity, bleeding, and other parameters were determined by analyzing the maize leaves and roots at 10, 20, 30, 40, and 50 days after flowering. Hemin enhanced the chlorophyll content and net photosynthetic rate of leaves; delayed leaf senescence; improved the accumulation and distribution of photosynthetic products; optimized the parameters of maize root growth characteristics, root activity, and bleeding rate; and optimized the mineral elements and amino acid contents in root bleeding under cadmium stress in field. Furthermore, hemin improved the starch characteristics of maize grain filling, promoted the activity and gene expression of key enzymes in starch synthesis, and increased maize yield and the radiation, heat, and water use efficiency of plants, which realized the synergistic improvement of maize yield and efficiency under cadmium stress. Hemin promoted the growth and development of maize leaves and roots under cadmium stress in field. The maize yield and radiation, heat, and water use efficiency were also improved synergistically, which provided technical methods for the maize production of stress resistance.

Cultivation models and mulching strategies to improve root-bleeding sap, nutrients uptake and wheat production in semi-arid regions

Article

Feb 2022
AGR WATER MANAGE

The application of mulching materials has significantly improved the production of wheat in semi-arid regions. However, various mulching applications under different tillage practices, whether it can improve the root growth, spatial distribution of root, nutrients uptake and grain yield of wheat is not clear. Therefore, a two years ﬁeld study was carried out during 2016–17 and 2017–18 to evaluate root growth, nutrients uptake, and wheat production under six treatments: CT: conventional planting; SM: wheat stalk mulching; FM: plastic mulching; RT: without plastic mulching with furrow and ridge planting; RP: plastic mulching with furrow and ridge planting; RPS: plastic mulching on ridges and stalk mulching on furrows. Under the RPS treatment, root biomass, soil moisture, soil enzymatic activity, and microbial abundance can be significantly improved, thus promoting root growth, nutrient absorption, and wheat production. The RPS treatment significantly improved the rooting system in the upper soil profile of 50 cm, which helped increase the yield of wheat. At various wheat growth stages, the RPS and RT treatment at the depth of 10–50 cm significantly increased root bleeding saps, and RLD, and reached up to the highest value at 125 DAP. However, there were no differences in RLD between the six different treatment methods in deeper soil profiles below 60 cm. In addition, during 2016–17 and 2017–18, the NH4⁺ and NO3⁻ delivery rates under the RPS were significantly higher than that of FM and RT, while the delivery rates of NH4⁺ and NO3⁻ under the RP treatment were maximum compared with FM practice. Under the RPS and RT treatments, the Fe, Ca, P, Zn, K, and Mg delivery rates were significantly maximum. In summary, RPS farming practices have been great potential to improve the rhizosphere environment, root biomass, and wheat yield in semi-arid regions.

Nitrogen fertilization and planting models regulate maize productivity, nitrate and root distributions in semi-arid regions

Article

Jun 2020
SOIL TILL RES

Shortages in soil water and nutrients resources, and low water productivity, are convincing growers to implement a sustainable water saving technology. Production of maize is greatly affected by nitrogen fertilization and planting models strategies through regulating root and (NO3⁻-N) distributions. In this study, we established two planting models, i.e. furrow planting with ridges film mulching (PN); traditional flat cultivation (TN), with four 0, 150, 250 and 350 kg N ha⁻¹ fertilization levels. The results indicated that the effect of planting models in combination of N fertilization levels on soil moisture, root distribution and maize production were significant. The total root length (TRL), total root dry weight (TRDW) and average root diameter (ARD) under the TN occurred the appearance peak time (te) and maximum growth rate (tm) more earlier, whereas those in PN treatments delayed under various N levels. The average growth rate (Ć), maximum growth rage (cm) and maximum values (Wmax) of ARD, TRDW and TRL were significantly higher under the PN350 and PN250 than that of TN treatments. The gray correlation coefficients in the middle and lower depths of soil among ARD, RDWD and RLD under the PN were remarkably maximum then those in TN under various N levels. These gray coefficients in the top soil profile of 0−40 cm were significantly lower under the PN, whereas these coefficients above 60 cm soil depths were clearly greater compared with TN. The increased RDWD, RLD and ARD under the PN350 treatment help to develop the root system, improve the water and nutrient absorption ability in deeper depths of soil, as a result significantly improve grain yield (58 %), RUE (49 %) and AEN (38 %) of maize than that of TN350 treatment. In the upper-most (0−10 cm) depth of soil the RLD was significantly higher at flowering and maturity stage under PN350 compared with TN350 treatment. In addition, at the deeper soil layer below 40 cm, there were no significant variations in RLD. Under PN treatment significantly improved, the root bleeding sap at jointing and flowering stage. In addition, the NO3⁻-N contents under PN350 were significantly higher than those under TN treatments. The above results indicated that PN350 and PN250 improve RUE, AEN and maize production by regulating root and (NO3⁻-N) distribution.

Absorción de nutrientes por las raíces y transporte dentro de la planta

Chapter

Full-text available

Nov 2014

Francisco Albornoz

Las raíces son los órganos de las plantas encargados de la absorción de agua y nutrientes desde el suelo. Tanto la absorción como el posterior transporte de los nutrientes dentro de la planta están altamente regulados a nivel celular y molecular, con el fin de satisfacer los requerimientos para la producción de nueva materia vegetal, lo que en el caso de árboles frutales, representa la producción de madera del año, hojas, raíces y, principalmente, frutos. Existen 17 nutrientes requeridos para el crecimiento y normal funcionamiento de las plantas, de los cuales tres son obtenidos desde la atmósfera y el agua: carbono (C), hidrógeno (H) y oxígeno (O). Los restantes elementos han sido divididos en tres grupos, según la cantidad relativa absorbida por las plantas. En el primer grupo, conocido como macronutrientes primarios, se encuentran el nitrógeno (N), fósforo (P) y potasio (K). Luego están los macronutrientes secundarios, donde se incluyen el calcio (Ca), magnesio (Mg) y azufre (S). Finalmente se encuentran los micronutrientes, donde se agrupan el hierro (Fe), boro (B), cobre (Cu), manganeso (Mn), molibdeno (Mo), zinc (Zn), níquel (Ni) y cloro (Cl). Cada uno de estos elementos cumple una función única e irremplazable en el metabolismo y desarrollo de las plantas, razón por la cual son conocidos como elementos esenciales (Marschner, 2012). En el presente capítulo se detallarán los mecanismos de absorción de los macro y micronutrientes en las raíces y los sistemas de transporte dentro de las plantas.

Application of paclobutrazol affect maize grain yield by regulating root morphological and physiological characteristics under a semi-arid region

Article

Full-text available

Mar 2018

A field experiment was conducted to investigate the effects of paclobutrazol on ear characteristics and grain yield by regulating root growth and root-bleeding sap of maize crop. Seed-soaking at rate of 0 (CK1), 200 (S1), 300 (S2), and 400 (S3) mg L-1, and seed-dressing at rate of 0 (CK2), 1.5 (D1), 2.5 (D2), and 3.5 (D3) g kg-1were used. Our results showed that paclobutrazol improved the ear characteristics and grain yield, and were consistently higher than control during 2015-2016. The average grain yield of S1, S2 and S3 were 18.9%, 61.3%, and 45.9% higher, while for D1, D2 and D3 were 20.2%, 33.3%, and 45.2%, compared to CK, respectively. Moreover, paclobutrazol-treated maize had improved root-length density (RLD), root-surface area density (RSD) and root-weight density (RWD) at most of the soil profiles (0-70 cm for seed-soaking, 0-60 cm for seed-dressing) and was attributed to enhancing the grain yield. In addition, root-activity, root-bleeding sap, root dry weight, diameter and root/shoot ratio increased by paclobutrazol, with highest values achieved in S2 and D3 treatments, across the whole growth stages in 2015-2016. Our results suggested that paclobutrazol could efficiently be used to enhance root-physiological and morphological characteristics, resulting in higher grain yield.

Effects of K-Mg Ratio on Growth and Cation Nutrition of Vitis vinifera L. cv. “Dattier de Beiruth” Grafted on SO 4 Rootstock

Article

Sep 2015

The area of planting of Vitis vinifera L. cv. Dattier de Beiruth (DB) grafted on the SO4 (Selection OPPENHEIM 4) rootstock is significant and constantly growing in Northern Algeria. A hydroponic culture was carried out with DB to investigate the effects of potassium-magnesium (K-Mg) ratio on plant growth and mineral nutrition. Four nutrient solutions were tested on which the K-Mg ratio is variable (nutritive solution (NS)1 = 0.3K: 3.8Mg, NS2 = 2.1K: 2Mg, NS3 = 2.6K: 1.5Mg and NS4 = 3.8K: 0.3Mg). The results showed that DB was characterized by a high capacity for K uptake. No significant differences among the treatments were detected in the leaf concentrations of calcium (Ca), however Mg uptake was inhibited by increase of K: Mg in the nutrient solution. Results showed that DB is sensitive to the variation of the cation composition in the nutrient solution. Antagonism between K-Mg was apparent.

The PhoP/Q two-component regulatory system is essential for Xylella fastidiosa survival in Vitis vinifera grapevines

Article

Dec 2014

Xylella fastidiosa is a gram-negative, xylem-limited plant pathogenic bacterium that causes disease in a variety of economically important agricultural crops including Pierce’s disease of grapevines. Quorum sensing is essential for Xylella fastidiosa to mediate pathogenicity in Vitis vinifera grapevines and subsequent transmission to other grapevines. Quorum sensing processes are regulated, to varying extent, by two-component regulatory systems. Here, we investigate the role of the PhoP/PhoQ two-component regulatory system, which is known to be involved in pathogenicity and survival of gram-negative bacterial pathogens of plants, humans and animals. Using insertional mutagenesis, we demonstrate that the PhoP/PhoQ two-component regulatory system is essential for Xylella fastidiosa survival in Vitis vinifera grapevines. Furthermore, we show PhoP/PhoQ is involved in regulation of density-dependent processes in vitro such as cell-cell aggregation and biofilm formation. We attempted to complement phoP and phoQ using the Pax1CM vector but were unsuccessful in generating a phoQ complement. The phoP complement we generated did not completely restore the wild-type phenotype although it did restore wild-type levels of phoP expression when the complement was grown on PD3 media. Our findings presented here demonstrate PhoP/PhoQ is responsible for regulating processes essential for Xylella fastidiosa survival in Vitis vinifera grapevines.

Effect of root restriction on nitrogen levels and glutamine synthetase activity in ‘Kyoho’ grapevines

Article

Apr 2012
SCI HORTIC-AMSTERDAM

To unravel the inhibition of root restriction on shoot growth, the changes of nitrogen levels and glutamine synthetase (GS, EC 6.3.1.2) activity were investigated in four-year-old root-restricted ‘Kyoho’ grapevines (Vitis vinifera × Vitis labrusca) in greenhouse from veraison up until 62 days after harvest. ‘Kyoho’ grapevines were planted in buried bed as root restriction and in raised bed (unrestricted rooting zone) as the control. Results showed that root restriction significantly decreased the total amount of N in leaves, berry flesh, white and brown roots, (NO3− + NO2−)–N content in leaves, white and brown roots, and NH4+–N content in brown roots. In addition, root restriction reduced not only N remobilization and recycling from leaves to roots after harvest, but also the total GS activity in both leaves and roots, suggesting that root restriction has a negative influence on glutamine synthesis in grapevines. However, soluble protein content in both leaves and white roots significantly increased under root restriction from 118 to 180 days after anthesis (DAA). It can be attributed to the increased synthesis of polypeptides and/or the enhanced de novo synthesis of proteins in root-restricted vines. In summary, the results illustrated less N reserve in root-restricted vines, which might be responsible for shoot growth inhibition under root restriction.

Measurement of xylem sap amino acid concentrations in conjunction with whole tree transpiration estimates spring N remobilization by cherry (Prunus avium L.) trees

Article

Dec 2002
PLANT CELL ENVIRON

Prunus avium trees were grown in sand culture for one vegetative season with contrasting N supplies, in order to precondition their N storage capacities. During the spring of the second year a constant amount of 15N was supplied to all the trees, and the recovery of unlabelled N in the new biomass production was used as a direct measure of N remobilization. Destructive harvests were taken during spring to determine the pattern of N remobilization and uptake. Measurements of both xylem sap amino acid profiles and whole tree transpiration rates were taken, to determine whether specific amino acids are translocated as a consequence of N remobilization and if remobilization can be quantified by calculating the flux of these amino acids in the xylem. Whereas remobilization started immediately after bud burst, N derived from uptake by root appeared in the leaves only 3 weeks later. The tree internal N status affected both the amount of N remobilization and its dynamics. The concentration of xylem sap amino acids peaked shortly after bud burst, concurrently with the period of fastest remobilization. Few amino acids and amides (Gln, Asn and Asp) were responsible for most of N translocated through the xylem; however, their relative concentration varied over spring, demonstrating that the transport of remobilized N occurred mainly with Gln whereas transport of N taken up from roots occurred mainly with Asn. Coupling measurements of amino acid N in the xylem sap with transpiration values was well correlated with the recovery of unlabelled N in the new biomass production. These results are discussed in relation to the possibility of measuring the spring remobilization of N in field-grown trees by calculating the flux of N translocation in the xylem.

Calcium Increases Xylella fastidiosa Surface Attachment, Biofilm Formation, and Twitching Motility

Article

Full-text available

Dec 2011
APPL ENVIRON MICROB

Xylella fastidiosa is a plant-pathogenic bacterium that forms biofilms inside xylem vessels, a process thought to be influenced by the chemical composition of xylem sap. In this work, the effect of calcium on the production of X. fastidiosa biofilm and movement was analyzed under in vitro conditions. After a dose-response study with 96-well plates using eight metals, the strongest increase of biofilm formation was observed when medium was supplemented with at least 1.0 mM CaCl2. The removal of Ca by extracellular (EGTA, 1.5 mM) and intracellular [1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester (BAPTA/AM), 75 μM] chelators reduced biofilm formation without compromising planktonic growth. The concentration of Ca influenced the force of adhesion to the substrate, biofilm thickness, cell-to-cell aggregation, and twitching motility, as shown by assays with microfluidic chambers and other assays. The effect of Ca on attachment was lost when cells were treated with tetracycline, suggesting that Ca has a metabolic or regulatory role in cell adhesion. A double mutant (fimA pilO) lacking type I and type IV pili did not improve biofilm formation or attachment when Ca was added to the medium, while single mutants of type I (fimA) or type IV (pilB) pili formed more biofilm under conditions of higher Ca concentrations. The concentration of Ca in the medium did not significantly influence the levels of exopolysaccharide produced. Our findings indicate that the role of Ca in biofilm formation may be related to the initial surface and cell-to-cell attachment and colonization stages of biofilm establishment, which rely on critical functions by fimbrial structures.

Soil microbial activities and carbon and nitrogen fixation

Article

Jul 2003
RES MICROBIOL

Soil microbial activity that reflects microbiological processes of soil microorganisms is the potential indicator of soil quality, as plants rely on soil microorganisms to mineralize organic nutrients for growth and development. Soil microorganisms also process plant litter and residues into soil organic matter, a direct and stable reservoir of carbon and nitrogen that consists of living and dead organic materials subject to rapid biological decomposition. In natural systems, the action of soil microorganisms is a major determinant of efficient nutrient cycling. This paper reviews the current state of knowledge on the fate of soil microorganisms in terms of carbon and nitrogen fixation.

Carbon and nitrogen partitioning in Vitis vinifera L.: Responses to nitrogen supply and limiting irradiance

Article

Full-text available

Jan 1995
VITIS

Ammonium Nutrition in Ricinus communis : Its Effect on Plant Growth and the Chemical Composition of the Whole Plant, Xylem and Phloem Saps

Article

Full-text available

Nov 1986

Allen, S. and Smith, J A. C. 1986. Ammonium nutrition in Ricinus communis: its effect on plantgrowth and the chemical composition of the whole plant, xylem and phloem saps.—J. exp. Bot. 37: 1599–1610. The growth and chemical composition of Ricinus communis cultivated hydroponically on 12 mol m − 3 NO3⁻-N were compared with plants raised on a range of NH4⁺-N concentrations. At NH4⁺-N concentrations between 0·5 and 4·0 mol m⁻³, fresh- and dry-weight yields of 62-d-old plants were not significantly different from those of the NO3⁻-N controls. Growth was reduced at 0·2 mol m⁻³ NH4⁺-N and was associated with increased root. shoot and C: organic N ratios, suggesting that the plants were N-limited. At 8·0 mol m⁻³ NH4⁺-N, growth was greatly restricted and the plants exhibited symptoms of severe ‘NH4⁺ toxicity’. Plants growing on NH4⁺-N showed marked acidification of the rooting medium, this effect being greatest on media supporting the highest growth rates. Shoot carboxylate content per unit dry weight was lower at most NH4⁺-N concentrations than in the NO3⁻-N controls, although it increased at the lowest NH4⁺-N levels. Root carboxylate content was comparable on the two N sources, but also increased substantially at the lowest NH4⁺-N levels. N source had little effect on inorganic-cation content at the whole-plant level, while NO3⁻ and carboxylate were replaced by Cl⊸ as the dominant anion in the NH4⁺-N plants. This was reflected in the ionic composition of the xylem and leaf-cell saps, the latter containing about 100 mol m⁻³ Cl⁻ in plants on 8·0 mol m⁻³ NH4⁺. Xylem-sap organic-N concentration increased more than threefold with NH4⁺-N (with glutamine being the dominant compound irrespective of N source) while in leaf-cell sap it increased more than 12-fold on NH4⁺-N media (with arginine becoming the dominant species). In the phloem, N source had little or no effect on inorganic-cation, sucrose or organic-N concentrations or sap pH, but sap from NH4⁺-N plants contained high levels of Cl⁻ and serine. Collectively, the results suggested that the toxic effects of high NH4⁺ concentrations were not the result of medium acidification, reduced inorganic-cation or carboxylate levels, or restricted carbohydrate availability, as is commonly supposed. Rather, NH4⁺ toxicity in R. communis is probably the result of changes in protein N turnover and impairment of the photorespiratory N cycle.

Physiological processes limiting plant growth in saline soils: Some dogmas and hypotheses

Article

Full-text available

Jan 1993
PLANT CELL ENVIRON

Rana Munns

Recent progress in improving the salt tolerance of cultivated plants has been slow. Physiologists have been unable to define single genes or even specific metabolic processes that molecular biologists could target, or pinpoint the part of the plant in which such genes for salt tolerance might be expressed. While the physiological might be expressed. While the physiological processes are undoubtedly complex, faster progress on unraveling mechanisms of salt tolerance might be made if there were more effort to test hypotheses rather than to accumulate data, and to integrate cellular and whole plant responses. This article argues that salts taken up by the plant do not directly control plant growth by affecting turgor, photosynthesis or the activity of any one enzyme. Rather, the build-up of salt in old leaves hasten their death, and the loss of these leaves affects the supply of assimilates or hormones to the growing regions and thereby affects growth.

Effects of P deficiency on the uptake, flows and utilization of C, N and H 2 O within intact plants of Ricinus communis L

Article

Full-text available

Nov 1996

The influence of P deficiency on the uptake, flow and utilization of C, N and H 2 0 by intact NO 3 -fed castor bean plants { Ricinus communis L.) was studied over a 9 d period in the middle of their vegetative growth. The modelling techniques incorporated data on net increments or losses of C, N and H 2 O in plant parts, photosynthetic gains in and respiratory losses of C, molar C:N ratios of solutes in phloem and xylem sap and transpirational losses of H 2 0. Plant growth was inhibited within 3 d of withholding P supply and dry matter production was less than one-third of the controls. Leaf growth was particularly depressed, while root growth was much less affected than that of the shoot. Shoot:root ratio of low-P plants was 1.5 compared with 2.6 under P supply. Over the 9 d study period total plant C and N increased by 560 and 47 mmol, respectively, in the controls, but by only 113 and 6.9 mmol in the low-P treatment. The particularly low increment of N in P-deficient plants was due principally to decreased N0 3 - uptake. Flows of C and N during the study period were markedly different between control and P-deficient plants. The partitioning profile for C in P-deficient plants showed a dramatic inhibition of net photosynthesis and attendant photoassimilate flow. Proportional downward to upward allocation of carbon increased with increase in sink size of the root relative to shoot. This was reflected in greater relative allocation of C to root dry matter and root respiration than in P-sufficient plants, and suppressed cycling of C from root to shoot via xylem. Nitrogen intake and xylem transport to the shoot of P-deficient plants were only 15% of the control and, as in the case of C, downward allocation of N predominated over upward phloem translocation. Apart from these severe changes, however, the basic patterns of N flows including xylem-to-phloem and xylem-to-xylem transfer of N were not changed, a feature highlighting the vital nature of these transfer processes even under deficiency conditions. The alterations in flows and partitioning of C, N and H 2 O in response to low-P conditions are discussed in relation to the corresponding effects of moderate salt stress in Ricinus and the conclusion is reached that changes in nutrient flows under P deficiency were more highly co-ordinated than when plants experience salt stress. Flow profiles under P deficiency which favour root growth and activity are viewed as a means for increasing the potential capability of the plant to acquire P from the nutrient medium.

Concentrations and Transport of Solutes in Xylem and Phloem along the Leaf Axis of NaCl-treated Hordeum vulgare

Article

Full-text available

Sep 1990

Hordeum vulgare cv. California Mariout was established in sand culture at two different NaCl concentrations (0.5 mol m⁻³ ‘control’ and 100 mol m⁻³) in the presence of 6.5 mol m⁻³ K ⁺. Between 16 and 31 d after germination, before stem elongation started, xylem sap was collected by use of a pressure chamber. Collections were made at three different sites on leaves 1 and 3: at the base of the sheath, at the base of the blade, i.e. above the ligule, and at the tip of the blade. Phloem sap was collected from leaf 3 at similar sites through aphid stylets. The concentrations of K ⁺, Na⁺, Mg2⁺ and Ca²⁺ were measured. Ion concentrations in xylem sap collected at the base of leaves 1 and 3 were identical, indicating there was no preferential delivery of specific ions to older leaves. All ion concentrations in the xylem decreased from the base of the leaf towards the tip; these gradients were remarkably steep for young leaves, indicating high rates of ion uptake from the xylem. The gradients decreased with leaf age, but did not disappear completely. In phloem sap, concentrations of K⁺ and total osmolality declined slightly from the tip to the base of leaves of both control and salt-treated plants. By contrast, Na⁺ concentrations in phloem sap collected from salt-treated plants decreased drastically from 21 mol m⁻³ at the tip to 7.5 mol m⁻³ at the base. Data of K/Na ratios in xylem and phloem sap were used to construct an empirical model of Na⁺ and K⁺ flows within xylem and phloem during the life cycle of a leaf, indicating recirculation of Na⁺ within the leaf.

Effects of P deficiency on assimilation and transport of nitrate and phosphate in intact plants of castor bean (Ricinus communis L.)

Article

Full-text available

Jan 1997

An experimentally-based modelling technique was applied to describe quantitatively the uptake, translocation, storage, and assimilation of NO3- and H2PO4- over a 9 d period in mid-vegetative growth of sandcultured castor bean (Ricinus communis L.) which was fed 12 mM NO3- and either 0.5 or a severely limiting 0.005 mM H2PO4⁻. Model calculations were based on increments or losses of NO3- and reduced N or of H2PO4- and organic P in plant parts over the study period, on the concentrations of the above compounds in xylem and phloem sap, and on the previously determined flows of C and N in the same plants (Jeschke et al., 1996). Modelling allowed quantitative assessments of distribution of NO3- reduction and H2PO4- assimilation within the plant. In control plants 58% of total NO3- reduction occurred in leaf laminae, 40% in the root and 2% in stem and apical tissues. Averaged over all leaves more than half of the amino acids synthesized in laminae were exported via phloem, while the root provided 2.5-fold more amino acids than required for root growth. P deficiency led to severe inhibition of NO3- uptake and transport in xylem and even greater depression of NO3- reduction in the root but not in the shoot. Accentuated downward phloem translocation of amino acids favoured root growth and some cycling of N back to the shoot. In control plants H2PO4- was the principal form of P transported in xylem with young laminae acting as major sinks. At the stem base retranslocation of P in the phloem amounted to 30% of xylem transport. H2PO4- assimilation was more evenly distributed than NO3- reduction with 54% occurring in leaf laminae, 6% in the apical bud, 19% in stem tissues, 20% in the root; young tissues were more active than mature ones. In P-deficient plants H2PO4- uptake was severely decreased to 1.8% of the control. Young laminae were the major sink for H2PO4- . Considerable remobilization of P from older leaves led to substantial shoot to root translocation via phloem (50% of xylem transport). Young leaf laminae were major sites of H2PO4- assimilation (50%), followed by roots (26%) and the apical bud (10%). The remaining H2PO4- was assimilated in stem and mature leaf tissues. Old leaves exhibited ‘negative’ net assimilation of H2PO4-, i.e. hydrolysis of organic P exceeded phosphorylation. In young laminae of low P plants, however, rates of H2PO4- assimilation per unit fresh weight were comparable to those of the controls.

The uptake and flow of C, N and ions between roots and shoots in Ricinus communis L. IV. Flow and metabolism of inorganic nitrogen and malate depending on nitrogen nutrition and salt treatment

Article

Full-text available

Mar 1996

Ricinus plants were supplied with nutrient solutions containing different N-sources or different nitrate concentrations and were also exposed to mild salinity. Between 41 and 51 d after sowing, the ratio of inorganic to total nitrogen in xylem and phloem saps, the content of inorganic nitrogen and malate in tissues, and nitrate reductase activities were determined. The flows of nitrate, ammonium, and malate between root and shoot were modelled to identify the site(s) of inorganic nitrogen assimilation and to show the possible role of malate in a pH-stat mechanism. Only in the xylem of nitrate-fed plants did inorganic nitrogen, in the form of nitrate, play a role as the transport solute. The nitrate percentage of total nitrogen in the xylem sap generally increased in parallel with the external nitrate concentration. The contribution of the shoot to nitrate reduction increased with higher nitrate supply. Under salt treatment relatively more nitrate was reduced in the root as compared with non-treated plants. Ammonium was almost totally assimilated in the root, with only a minor recycling via the phloem. Nitrate reductase activities measured in vitro roughly matched, or were somewhat lower than, calculated rates of nitrate reduction. From the rates of nitrate reduction (OH -production) and rates of malate synthesis (2H+-production) it was calculated that malate accumulation contributed 76, 45, or 39% to the pH-stat system during nitrate reduction in plants fed with 0.2, 1.0 or 4.0 mM nitrate, malate flow in the phloem played no role. In tissues of ammonium-fed plants no malate accumulation was found and malate flows in xylem and phloem were also relative low.

The Transport of Water from Soil to Shoot in Wheat Seedlings

Article

Full-text available

Feb 1980

JB Passioura

A technique is described for precisely measuring the drop in water potential, Δψ, between the soil and the leaf xylem of wheat seedlings. The technique was used to explore the relation between transpiration rate and Δψ at various times during the monotonic drying of the soil in which the plants were growing. When the soil was wet, the relation was linear, but, as the soil dried, nonlinearities appeared which were, in the main, explicable in terms of simple soil physical models describing the flow of water through the soil to the roots. There was no sign of the major hydraulic resistance at the root: soil interface that other people have recently found.

Influence of Nitrate and Ammonium Nutrition on the Uptake, Assimilation, and Distribution of Nutrients in Ricinus communis

Article

Full-text available

Apr 1988
PLANT PHYSIOL

Ricinus communis L. plants were grown in nutrient solutions in which N was supplied as NO(3) (-) or NH(4) (+), the solutions being maintained at pH 5.5. In NO(3) (-)-fed plants excess nutrient anion over cation uptake was equivalent to net OH(-) efflux, and the total charge from NO(3) (-) and SO(4) (2-) reduction equated to the sum of organic anion accumulation plus net OH(-) efflux. In NH(4) (+)-fed plants a large H(+) efflux was recorded in close agreement with excess cation over anion uptake. This H(+) efflux equated to the sum of net cation (NH(4) (+) minus SO(4) (2-)) assimilation plus organic anion accumulation. In vivo nitrate reductase assays revealed that the roots may have the capacity to reduce just under half of the total NO(3) (-) that is taken up and reduced in NO(3) (-)-fed plants. Organic anion concentration in these plants was much higher in the shoots than in the roots. In NH(4) (+)-fed plants absorbed NH(4) (+) was almost exclusively assimilated in the roots. These plants were considerably lower in organic anions than NO(3) (-)-fed plants, but had equal concentrations in shoots and roots. Xylem and phloem saps were collected from plants exposed to both N sources and analyzed for all major contributing ionic and nitrogenous compounds. The results obtained were used to assist in interpreting the ion uptake, assimilation, and accumulation data in terms of shoot/root pH regulation and cycling of nutrients.

Effects of nitrogen source, nitrate concentration and salt stress on element and ion concentrations in transport fluids and on C and N flows in Ricinus communis L.

Chapter

Jan 1995

Ricinus communis L. was supplied with 0.2, 1.0, 4.0 mM nitrate or 1.0 mM ammonium and treated with a mild salt stress 40 mM NaCl (1.0 mM nitrate or ammonium). Between 41 and 52 days after sowing, element and ion concentrations in xylem and phloem sap were determined, and flows of C and N were modelled. Nutritional conditions particularly affected anion concentrations in the root-pressure xylem sap. Nitrate was the major N-compound in xylem sap of nitrate-fed, and amino acids in that of ammonium-fed plants. Lower nitrate was compensated mainly by chloride as an anion and by amino acids as a N-solute. Under salt treatment, Na+ and Cl-levels increased, but a high selectivity ofion uptake into the xylem was observed. The phloem sap was less affected by nutritional conditions; only under stress conditions higher ion concentrations in the xylem, i.e. mainly of Na+ and Cl-, reflected in the phloem sap. Most of the N taken up was first transported to the shoot. In plants provided with adequate N, 70 -77% of the N was incorporated into the shoot. This partitioning was shifted in favour of the shoot in salt-stressed, and in favour of the root, in N-limited plants, in which a net export of N from the shoot occurred. Salt stress and N-limitation decreased the photosynthetic and respiratory rates in Ricinus shoots, root respiration was stimulated by ammonium assimilation. Higher N assimilation in the root increased the proportion of C transported to the root, which was used there for respiration. Concomitantly more amino acids were translocated and led to higher recycling of carbon to the shoot via the xylem.

Abscisic Acid—A Hormonal Long-Distance Stress Signal in Plants Under Drought and Salt Stress

Chapter

May 1999

When Abscisic Acid (ABA) is applied externally to plants, their water relations are improved. ABA reduces water loss by promoting stomatal closure and can increase water uptake into roots. ABA application also promotes characteristic developmental changes that can help the plant cope with a range of environmental stresses. Examples of such changes are the restricted growth of shoots, the reduction in leaf surface area, a stimulation of root extension, lateral root growth, and root hair development. All these effects of ABA application, together with the observation that environmental stress stimulates ABA biosynthesis and ABA release from sites of synthesis to the sites of action, suggest a role for ABA as a stress hormone in plants.

Effect of soil type on nitrate uptake by wheat shoots characterized using 15N-labelled NH4 NO3-fertilizer and in vitro, leaf nitrate reductase activity

Article

Jan 1998

Wheat plants grown in a greenhouse in containers filled with chalky (CP) or loamy (LP) soil were fertilized with NH415NO3 or 15NH4 NO3 (5 atom% 15N), initial soil nitrate levels being lower in chalky soil. Both the total amount of nitrate and the proportion derived from fertilizer were higher in leaves of plants grown on chalky soil, however, increased inorganic N was not paralleled by a higher organic N content in the CP leaves. In vitro NR activity of the youngest fully expanded leaves confirmed that NO3 flux into the shoot was higher for CP than for LP. The ratio of the ‘proportion of fertilizer in the flag leaf NO3 pool divided by the proportion of fertilizer in the soil total N pool’ reached a maximum (0.8) at the onset of the flag leaves for CP but decreased to 0.5 at the time of flowering because stored NO3 from fertilizer was predominantly re-used to feed other parts of the plants. In LP, NO3 was not remobilized and the ratio remained at 0.8. Higher in vitro NR activity in the CP flag leaf confirmed that release and re-use of stored nitrate occurred and that plants grown on chalky soils appear to have an enhanced ability to utilise nitrate.

Modelling of the Uptake, Flow and Utilization of C, N and H2O within Whole Plants of Ricinus communis L. Based On Empirical Data

Article

Feb 1991
J PLANT PHYSIOL

An empirically based modelling technique was used to quantitatively depict uptake, flow and utilization of C, N and H2O for a 9 day period in mid vegetative growth of NO3-fed castor bean (Ricinus communis L.) exposed to a mean salinity stress of 128 mol m-3 NaCl. The models incorporated data on C : N weight ratios of solutes of phloem sap and pressure-induced xylem exudates of leaves, stem internodes and petioles, net increments or losses of C, N and H2O in plant parts, transpirational losses of shoot organs and respiratory losses of C from shoot parts and root. A computational technique was developed to assess the extent of xylem to phloem transfer of C and N within internally sited organs (stem segments and petioles) in addition to traffic of C and N through these organs to terminal organs (root, shoot apex and leaves). Molar ratios of inputs of H2O: C : N were 4803: 22: 1. Half of the net daytime photosynthetic gain of C by the shoot was translocated initially to the root, 33 % was lost in root respiration, 17% in shoot night respiration, 8% cycled through the root system and 40% was finally incorporated into shoot dry matter, 10% into root dry matter. The corresponding N budget showed 93% initial transfer in xylem from root to leaf laminae, 32% backflow in phloem from shoot to root and 15 % cycled through the root. The water budget involved a 98% loss in transpiration, 2% incorporation into tissues and 2% commitment to phloem transport. Xylem to phloem exchanges of C and N in shoot mostly involved transfer from xylem to phloem. The models predicted a steep upward gradient in decreasing water use efficiency with leaf age, due principally to poor CO2 fixation in relation to water loss by youngest leaves. Comparison of fluxes of N and H2O between stem internode segments with those passing out to leaves indicated progressive lateral abstraction of N from leaf traces serving lower leaves and subsequent passage of this N to the xylem of cauline traces serving upper regions of the shoot. Data were compared with earlier obtained information on C, N and H2O partitioning in nodulated white lupin (Lupinus albus L.).

The uptake and flow of C, N and ions between roots and shoots in Ricinus communis L. III. Long-distance transport of abscisic acid depending on nitrogen nutrition and salt stress

Article

Jun 1994

Seedlings of Ricinus communis L. were cultivated in quartz sand and supplied with media which contained either different concentrations of nitrate or ammonium nitrogen and were treated with a low salt stress. The concentration of ABA was determined in tissues and in xylem and phloem saps. Between 41 and 51 day after sowing, abscisic acid (ABA) flows between roots and shoots were modelled. Long-distance transport of ABA was not stimulated under conditions of nitrate deficiency (0.2 mol m−3). However, when ammonium was given as the only N source (1.0 mol m−3), ABA transport in both xylem and phloem was increased significantly. Mild salt stress (40 mol m−3 NaCl) increased ABA transport in nitrate-fed plants, but not in ammonium-fed plants. The leaf conductance was lowered by salt treatment with both nitrogen sources, but it was always lower in ammonium-fed compared to nitrate-fed plants. A negative correlation of leaf conductance to ABA levels in leaves or flow in xylem was found only in comparison of ammonium-fed to nitrate-fed plants.

The Uptake and Flow of C, N and lons between Roots and Shoots in Ricinus communis L

Article

Jul 1993

Seedlings of Ricinus communis L. cultivated in quartz sand were supplied with a nutrient solution containing either 1 mol m⁻³ NO⁻3 or 1 mol m⁻³ NH⁺4 as the nitrogen source. During the period between 41 and 51 d after sowing, the flows of N, C and inorganic ions between root and shoot were modelled and expressed on a fresh weight basis. Plant growth was clearly inhibited in the presence of NH⁺4. In the xylem sap the major nitrogenous solutes were nitrate (74%) or glutamine (78%) in nitrate or ammonium-fed plants, respectively. The pattern of amino acids was not markedly influenced by nitrogen nutrition; glutamine was the dominant compound in both cases. NH⁺4 was not transported in significant amounts in both treatments. In the phloem, nitrogen was transported almost exclusively in organic form, glutamine being the dominant nitrogenous solute, but the N-source affected the amino acids transported. Uptake of nitrogen and carbon per unit fresh weight was only slightly decreased by ammonium. The partitioning of nitrogen was independent of the form of N-nutrition, although the flow of nitrogen and carbon in the phloem was enhanced in ammonium-fed plants. Cation uptake rates were halved in the presence of ammonium and lower quantities of K⁺, Na⁺ and Ca²⁺ but not of Mg²⁺ were transported to the shoot. As NH⁺4 was balanced by a 30-fold increase in chloride in the solution, chloride uptake was increased 6-fold under ammonium nutrition. We concluded that ammonium was predominantly assimilated in the root. Nitrate reduction and assimilation occurred in both shoot and root. The assimilation of ammonium in roots of ammonium-fed plants was associated with a higher respiration rate.

Partitioning Control by Water Potential Gradient: Evidence for Compartmentation Breakdown in Grape Berries

Article

Sep 1991

Alexander Lang

Xylem exudate was obtained from berries of Riesling grapes at different stages of development after the onset of ripening using a pressure bomb technique. The osmotic potential of the exudate bore a 1:1 relationship to that of juice from the same berries which were afterwards crushed and centrifuged. This result provides the first direct evidence of compartmentation breakdown in grape berries after the onset of ripening. Changes in berry deformability which occur at the same time and measurements of the dynamics of exudation flow lead to the same conclusion regarding compartmentation breakdown. The breakdown in compartmentation occurs at the same time as the rate of phloem translocation to the fruit suddenly increases. A mechanism was recently proposed to account for this increase. It required the existence of a water potential difference between source and sink such as would result from compartmentation breakdown in the sink tissues. The results, therefore, may be taken to indicate that this mechanism is indeed involved in the control of assimilate partitioning in Vitis. Evidence in other publications suggests that the mechanism may be reasonably widespread in plants.

Cation and Chloride Partitioning through Xylem and Phloem within the Whole Plant of Ricinus communis L. under Conditions of Salt Stress

Article

Sep 1991

Uptake and partitioning through the xylem and phloem of K+, Na+, Mg2+ , Ca2+ and Cl− were studied over a 9 d interval during late vegetative growth of castor bean (Ricinus communis L.) plants exposed to a mean salinity stress of 128 mol m−3 NaCl. Empirically based models of flow and utilization of each ion within the whole plant were constructed using information on ion increments of plant parts, molar ratios of ions to carbon in phloem sap sampled from petioles and stem internodes and previously derived information on carbon flow between plants parts in xylem and phloem in identical plant material. Salient features of the plant budget for K+ were prominent deposition in leaves, high mobility of K+ in phloem, high rates of cycling through leaves and downward translocation of K+ providing the root with a large excess of K+ . Corresponding data for Na+ showed marked retention in the root, lateral uptake from xylem by hypocotyl, stem internodes and petioles leading to low intake by young leaf laminae and substantial cycling from older leaves back to the root. The partitioning of the anionic component of NaCl salinity, Cl−, contrasted to that of Na+ in that it was not substantially retained in the root, but deposited more or less uniformly in stem, petiole and leaf lamina tissues. The flow pattern for Mg2+ showed relatively even deposition through the plant but some preferential uptake by young leaves, generally lesser export than import by leaf laminae, and a return flow of Mg2+ from shoot to root considerably less than the recorded increment of the root. Ca2+ partitioning contrasted with that of the other ions in showing extremely poor phloem mobility, leading to progressive preferential accumulation in leaf laminae and negligible cycling of the element through leaves or root. Features of the response of Ricinus to salinity shown in the present study were discussed with data from similar modelling studies on white lupin (Lupinus albus L.) and barley (Hordeum vulgare L.)

Modelling of the Partitioning, Assimilation and Storage of Nitrate within Root and Shoot Organs of Castor Bean ( Ricinus communis L.)

Article

Sep 1991

An experimentally-based modelling technique was developed to describe quantitatively the uptake, flow, storage and utilization of NO3-N over a 9 d period in mid-vegetative growth of sand cultured castor bean (Ricinus communis L.) fed 12 mol m⁻³ nitrate and exposed to a mean salinity stress of 128 mol m⁻³ NaCl. Model construction used information on increments or losses of NO3-N or total reduced N in plant parts over the study period and concentration data for NO3-N and reduced (amino acid) N in phloem sap and pressure-induced xylem exudates obtained from stem, petiole and leaf lamina tissue at various levels up a shoot. The resulting models indicated that the bulk (87%) of incoming nitrate was reduced, 51% of this in the root, the remainder principally in the laminae of leaves. The shoot was 60% autotrophic for N through its own nitrate assimilation, but was oversupplied with surplus reduced N generated by the root and fed to the shoot through the xylem. The equivalent of over half (53%) of this N returned to the root as phloem translocate and, mostly, then cycled back to the shoot via xylem. Nitrate comprised almost half of the N of most xylem samples, but less than 1% of phloem sap N. Laminae of leaves of different age varied greatly in N balance. The fully grown lower three leaves generated a surplus of reduced N by nitrate assimilation and this, accompanied by reduced N cycling by xylem to phloem exchange, was exported from the leaf. Leaf 4 was gauged to be just self-sufficient in terms of nitrate reduction, while also cycling reduced N. The three upper leaves (5–7) met their N balance to varying extents by xylem import, phloem import (leaves 6 and 7 only) and assimilation of nitrate. Petioles and stem tissue generally showed low reductase activities, but obtained most of their N by abstraction from xylem and phloem streams. The models predicted that nodal tissue of lower parts of the stem abstracted reduced N from the departing leaf traces and transferred this, but not nitrate, to xylem streams passing further up the shoot. As a result, xylem sap was predicted to become more concentrated in N as it passed up the shoot, and to decrease the ratio of NO3-N to reduced N from 0·45 to 0·21 from the base to the top of the shoot. These changes were reflected in the measured N values for pressure-induced xylem exudates from different sites on the shoot. Transfer cells, observed in the xylem of leaf traces exiting from nodal tissue, were suggested to be involved in the abstraction process.

Crop Salt Tolerance-Current Assessment

Article

Jun 1977

An extensive literature review of all available salt tolerance data was undertaken to evaluate the current status of our knowledge of the salt tolerance of agricultural crops. In general, crops tolerate salinity up to a threshold level above which yields decrease approximately linearly as salt concentrations increase. Our best estimate of the threshold salinity level and yield decrease per unit salinity increase is presented for a large number of agricultural crops. The methods of measuring appropriate salinity and plant parameters to obtain meaningful salt tolerance data and the many plant, soil, water, and environmental factors influencing the plant's ability to tolerate salt are examined.

The uptake and flow of C, N and ions between roots and shoots in Ricinus communis L. II. Grown with low or high nitrate supply

Article

Jun 1994

Seedlings of Ricinus communis L. cultivated in quartz sand were supplied with a nutrient solution containing either 0.2 mol m(-3) NO3- or 4.0 mol m(-3) NO3- as the nitrogen source to obtain insufficiently (low supply, nitrogen-limited) or well-fed plants (high supply, control). During the period between 41 and 51 d after sowing, the flows of C, N and inorganic ions between root and shoot were modelled on the basis of empirical observation and expressed on a fresh weight basis. With a low nitrate supply the biomass production was decreased while the root/shoot ratio was drastically increased and the water content in the shoot was slightly reduced. Nitrogen was transported in the xylem mainly in the form of nitrate in both treatments. However, in nitrate-limited plants the ratio of nitrate to total nitrogen was lower, indicating a higher fraction of whole-plant nitrate reduction occurring in the root. The spectrum of amino acids in phloem sap was changed due to N-limitation. Nitrate and cation uptake, as well as photosynthesis was strongly decreased in nitrate-limited plants. The partitioning of C, N and ions was shifted in favour of the root compared to well-fed plants. Transport of C, N, and cations in the xylem was decreased. Flows of ions and elements in the phloem were increased relative to uptake and xylem transport. In contrast, the chloride flows were nearly the same in low- and well-fed plants, pointing to a role of chloride as a compensating ion for nitrate.

The Composition of Phloem Exudate and Xylem Sap from Broccoli ( Brassica oleracea var. italica) Supplied with NH 4 + , NO ⊟ 3 or NH 4 NO 3

Article

Oct 1987

Barry J Shelp

Shelp, B. J. 1987. The composition of phloem exudate and xylem sap from broccoli (Brassica oleracea var. italica) supplied with NH⁺4, NO⊟3 or NH4NO3.—J. exp. Bot. 38: 1619–1636. The detailed composition of xylem sap and exudate from stem incisions of attached inflorescences of broccoli (Brassica oleracea var. italica) was compared in plants supplied with NH⁺4, NO⊟3 or NH4NO3. A phloem origin for the exudate was suggested from the high levels of sugars (71–133 mg cm⁻³), amino acids (8·1-26·7 mg cm⊟3) and K. (2·3–3·8 mg cm⊟3), the low levels of NO⊟3 and Ca, the high C: N (w/w) ratios (8·3–33), and the alkaline pH (7·2–7·3). In contrast, the xylem sap was mildly acidic (pH 5·6–6·0), and possessed lower levels of all organic and inorganic solutes but NO⊟3 and Ca, and lower ratios of K: Ca, Mg: Ca and C: N (0·6–4·4). Glutamine was the predominant o-phthalaldehyde-reactive amino compound in both transport fluids with the next most abundant amino acids dependent on sap type and N-form. Together with arginine, γ-aminobutyric acid, which was found only in the xylem stream, was enhanced by NH⁺4compared to NO⊟3 -nutrition suggesting that glutamate metabolism was stimulated in the roots. Under limiting N the amino acid concentrations in the transport fluids were greater with NH⁺4 than with NO3⊟. NO3⊟ reduction occurred in both the root and shoot with the latter site predominating over the entire N range (0-300 mol m⊟3). Even though the composition of nitrogenous solutes in the xylem was dependent on cultivar and N source, the composition of the phloem streams supplying the developing inflorescence was relatively unaffected. The data on the element composition of organs and phloem sap are interpreted to suggest that, in spite of the restricted mobility of some elements such as B and Mn, a significant proportion of their total supply to developing sinks is carried in the phloem stream.

The concentration of xylem sap constituents in root exudate, and in sap from intact, transpiring castor bean plants (Ricinus communis L.)

Article

Apr 2006
PLANT CELL ENVIRON

Root exudates were sampled from detopped root systems of castor bean (Ricinus communis). Different volume flux rates were imposed by changing the pneumatic pressure around the root system using a Passioura-type pressure chamber. The concentrations of cations, anions, amino acids, organic acids and abscisic acid decreased hyperbolically when flux rates increased from pure root exudation up to values typical for transpiring plants. Concentrations at low and high fluxes differed by up to 40 times (phosphate) and the ratio of substances changed by factors of up to 10. During the subsequent reduction of flux produced by lowering the pneumatic pressure in the root pressure chamber, the concentrations and ratios of substances deviated (at a given flux rate) from those found when flux was increased. The flux dependence of exudate composition cannot therefore be explained by a simple dilution mechanism. Xylem sap samples from intact, transpiring plants were collected using a Passioura-type root pressure chamber. The concentrations of the xylem sap changed diurnally. Substances could be separated into three groups: (1) calcium, magnesium and amino acid concentrations correlated well with the values expected from their concentration-flux relationships, whereas (2) the concentrations of sulphate and phosphate deviated from the expected relationships during the light phase, and (3) nitrate and potassium concentrations in intact plants varied in completely the opposite manner from those in isolated root systems. Abscisic acid concentrations in the root exudate were dependent on the extent of water use and showed strong diurnal variations in the xylem sap of intact plants even in droughtstressed plants. Calculations using root exudates overestimated export from the root system in intact plants, with the largest deviation found for proton flux (a factor of 10). We conclude that root exudate studies cannot be used as the sole basis for estimating fluxes of substances in the xylem of intact plants. Consequences for studying and modelling xylem transport in whole plants are discussed.

Uptake, assimilation and transport of nitrogen compounds by plants

Article

Jan 1973
SOIL BIOL BIOCHEM

J. S. Pate

This paper reviews current knowledge and presents some new information on the metabolism of nitrogen in various species of higher plants.The role of the root system is considered. It is shown that the roots of many herbaceous and woody plants can manufacture organic compounds of nitrogen from the nitrate or other forms of inorganic nitrogen they absorb from the medium. The extent to which they do this varies greatly with the age and nutrition of the plant and with the environmental conditions under which it is growing. The relationship is examined between the synthetic activities of the root and its activity in upward transport of nitrogen to the shoot. The latter process takes place predominantly, if not exclusively, in the xylem, and in each species one or more nitrogen-rich compounds, e.g., amides, ureides and amino acids, carry the bulk of the nitrogen leaving the root. A second group of plants is described in which roots do not function to any extent in the reduction of nitrate.Consideration is given to the fate of recently absorbed nitrogen once it reaches the shoot system. An inorganic source such as nitrate, or molecules such as amides containing surplus amino groupings, are shown to serve as nitrogen sources for synthesis of amino acids required for protein synthesis. Some of these amino acids arise directly from the photosynthetic apparatus. Alternatively, surplus nitrogen arriving from the root may be stored in the shoot, from where it is drawn upon extensively if uptake by the root fails to keep pace with the shoot's demands for nitrogen.The transport system for nitrogen is examined for the whole plant. The classes of sources and sinks for nitrogen are described, and information presented on the types of nitrogenous solutes they receive from the xylem and phloem.

Monoclonal antibodies for the detection and quantitation of the endogenous plant growth regulator, abscisic acid

Article

Aug 1983

Monoclonal antibodies (mAB) have been produced which recognize the physiologically active 2-cis-(S-form of the endogenous plant growth regulator, abscisic acid (ABA). Cross-reaction with the ABA-catabolites, phaseic and dihydrophaseic acid, is negligible, and (R)-ABA, 2-trans-ABA, the ABA-conjugate, ABA-β-D-glucopyranosyl ester, as well as the putative ABA precursor, xanthoxin, are totally unreactive. In addition to being very specific, the mAB exhibit high affinites for 2-cis-(S)-ABA: the K values were 7.9 × 109 l/mol and 3.7 × 109 l/mol for antibodies from two different clones. By mAB-radioimmunoassay (RIA), 4 pg 2-cis-(S)-ABA (99.5% confidence level) can be detected. mAB-RIA can be used to quantitate ABA directly in unprocessed plant extracts.

Electrical Charge Balance in the Xylem Sap of Beet and Sorghum Plants grown with either NO3 or NH4 Nitrogen

Article

Nov 1986
J PLANT PHYSIOL

Beet (Beta vulgaris L. cv. Groeninga) and sorghum [Sorghum bicolor (L.) Moench cv. Bogor] seedlings were grown for 15-20 days in nutrient solution at a constant pH of 6.0 and with either NH4 or NO3 as nitrogen source. As compared with NO3-grown beet plants NH4-grown beet plants contained lower levels of cations (Ca, Mg, K) and higher levels of anions (H2PO4, Cl) in their shoots. In the roots of beet plants smaller differences in ionic composition were found between the two nitrogen sources. Mineral content of roots and shoots of sorghum plants was little affected by the external nitrogen source.In NO3-grown plants of both species, NO3 ions represented the main nitrogen component found in the xylem exudate, while NH4-grown plants transferred about 90% of the nitrogen in the xylem sap as electroneutral amides (mainly glutamine) and amino acids, and the rest in the form of NH4 ions. The absence of the negative charge of NO3 in the xylem sap of NH4-grown plants was compensated in both plant species by higher concentrations of malate and citrate, and in the case of beet plants also by an increase of the Ntot/total cation concentration ratio.Results are discussed in connection with electrical charge compensation, the (re-)distribution of cations and anions, and the control of internal pH during NO3- and NH4-nutrition.

Influence of the Form of Nitrogen Supply on Root Uptake and Translocation of Cations in the Xylem Exudate of Maize (Zea mays L)

Article

Nov 1993

Concentrations of inorganic cations are often lower in plants supplied with NH4⁺ as compared with NO3⁻. To examine whether this is attributable to impaired root uptake of cations or lower internal demand, the rates of uptake and translocation of K, Mg, and Ca were compared in maize plants (Zea mays L.) with different growth-related nutrient demands. Plants were grown in nutrient solution with either 1·0 mol m⁻³ NO3⁻ or NH4⁺ and the shoot growth rate per unit weight of roots was modified by varying the temperature of the shoot base (SBT) including the apical shoot meristem. The shoot growth rate per unit weight of roots, which was taken as the parameter for the nutrient demand imposed on the root system, was markedly lower at 12°C than at 24°C SBT. As a consequence of the lower nutrient demand at 12°C SBT, uptake rates of NO3⁻ and NH4⁺ declined by more than 50% Compared with NO3⁻ supply, NH4⁺ nutrition depressed the concentrations of K and particularly of Ca in the shoot, both in plants with high and with low nutrient demand. This indicates a control of cation concentration by internal demand rather than by uptake capacity of the roots. Translocation rates of K, Mg and Ca in the xylem exudate were lower in NH4⁺- than in NO3⁻-fed plants. Net accumulation rates of Ca in the shoot were also decreased, whereas net accumulation rates of K in the shoot were even higher in NH4⁺-fed plants. It is concluded that reduced cation concentrations in the xylem sap of plants supplied with NH4⁺ are due to the lower demand of cations for charge balance. The lower K translocation to the shoot is compensated by reduced retranslocation to the roots. For Ca, in contrast, decreased translocation rates in NH4⁺-fed plants result in lower shoot concentration.

Ion Channels in the Xylem Parenchyma of Barley Roots (A Procedure to Isolate Protoplasts from This Tissue and a Patch-Clamp Exploration of Salt Passageways into Xylem Vessels

Article

Aug 1994

To identify mechanisms for the simultaneous release of anions and cations into the xylem sap in roots, we investigated voltage-dependent ion conductances in the plasmalemma of xylem parenchyma cells. We applied the patch-clamp technique to protoplasts isolated from the xylem parenchyma by differential enzymic digestion of steles of barley roots (Hordeum vulgare L. cv Apex). In the whole-cell configuration, three types of cation-selective rectifiers could be identified: (a) one activated at membrane potentials above about -50 mV; (b) a second type of outward current appeared at membrane potentials above +20 to +40 mV; (c) below a membrane potential of approximately -110 mV, an inward rectifier could be distinguished. In addition, an anion-specific conductance manifested itself in single-channel activity in a voltage range extending from about -100 to +30 mV, with remarkably slow gating. In excised patches, K+ channels activated at hyperpolarization as well as at depolarization. We suggest that salt is released from the xylem parenchyma into the xylem apoplast by simultaneous flow of cations and anions through channels, following electrochemical gradients set up by the ion uptake processes in the cortex and, possibly, the release and reabsorption of ions on their way to the xylem.

Der Stickstoffexport der Wurzel und die Zusammensetzung des Xylemexsudats. Teil 1: Der Einfluß einer zunehmenden Stickstoffdüngung

Jan 1992
VITIS
121-130

G Alleweldt
N Merkt

Alleweldt, G., and N. Merkt. Der Stickstoffexport der Wurzel und die Zusammensetzung des Xylemexsudats. Teil 1: Der Einfluß einer zunehmenden Stickstoffdüngung. Vitis 31:121-130 (1992).

The nitrogen output of the root and the nitrogenous compounds in the xylem exudate. Part 2: The influence of grafting

Jan 1993
55-60

G Alleweldt
N Merkt

Alleweldt, G., and N. Merkt The nitrogen output of the root and the nitrogenous compounds in the xylem exudate. Part 2: The influence of grafting. Vitic. Enol. Sci. 48:55-60 (1993).

Solute exchange from xylem to phloem in the leaf and from phloem to xylem in the root. In: Recent Advances in Phloem Transport and Assimilate Compartimentation

Jan 1991
96-104

W D Jeschke
O Wolf
J S Pate

Jeschke, W. D., O. Wolf, and J. S. Pate. Solute exchange from xylem to phloem in the leaf and from phloem to xylem in the root. In: Recent Advances in Phloem Transport and Assimilate Compartimentation. J. L. Bonnemain et al. (Eds.) pp 96-104. Ouest Editions, Nantes (1991).

Jan 1991
1117-1122

Exp. Botany 42:1117-1122 (1991).

Die Mineralisation des organisch gebundenen Stickstoffs in Weinbergsböden. Teil I: Die N min -Dynamik

Jan 1991
VITIS
151-166

K Müller

Müller, K. Die Mineralisation des organisch gebundenen Stickstoffs in Weinbergsböden. Teil I: Die N min -Dynamik. Vitis 30:151-166 (1991).

Long distance transport of abscisic acid depending on nitrogen nutrition and salt stress

Jan 1994
741-747

Long distance transport of abscisic acid depending on nitrogen nutrition and salt stress. J. Exp. Botany 45:741-747 (1994).

Effect of K + supply on ion uptake and concentration in expressed root sap and xylem sap of several grapevine rootstock varieties

Jan 1993
61-68

E H Rühl

27. Rühl, E. H. Effect of K + supply on ion uptake and concentration in expressed root sap and xylem sap of several grapevine rootstock varieties. Viticulture Enol. Sci. 48:61-68 (1993).

Jan 1997
304-309

K Wahl
W Patzwahl

Wahl, K., and W. Patzwahl. Beziehungen zwischen Boden und Wein. Rebe und Wein 9:304-309 (1997).

The composition of phloem exudate and xylem sap from broccoli (Brassica oleracea var. italica) supplied with NH 4 + , NO 3-or NH 4 NO 3 Influence of nitrate and ammonium on the uptake, assimilation, and distribution of nutrients in Ricinus communis

Jan 1987
1619-1636914

B J M L Shelp
E A Kirkby
R Baas

Shelp, B.J. The composition of phloem exudate and xylem sap from broccoli (Brassica oleracea var. italica) supplied with NH 4 +, NO 3-or NH 4 NO 3. J. Exp. Botany 38:1619-1636 (1987). 30. van Beusichem, M. L., E. A. Kirkby, and R. Baas. Influence of nitrate and ammonium on the uptake, assimilation, and distribution of nutrients in Ricinus communis. Plant Physiol. 86:914-921 (1988).

Jan 1996
1737-1754

J Exp

J. Exp. Botany 47:1737-1754 (1996).

The Chemical Composition of Xylem Sap in Vitis vinifera L. cv. Riesling During Vegetative Growth on Three Different Franconian Vineyard Soils and as Influenced by Nitrogen Fertilizer

Abstract

No full-text available

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