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Relationship between potassium fertilisation and nitrate assimilation in leaves and fruits of cucumber (Cucumis sativus) plants
Abstract
The effect of application of different potassium rates on some parameters of nitrate metabolism and yield in cucumber plants (Cucumis sativus) was studied. All plants were grown under controlled conditions in an experimental greenhouse. The treatments consisted of applications of K+ at three rates in the form of K2SO4 (Kl: 0.075 mg ml−1, K2: 0.15 mg ml−1, and K3: 0.30 mg ml−1). The results showed a positive effect of higher K+ fertilisation (0.30 mg ml−1) on uptake, translocation and reduction of NO3− in leaves compared with the lowest K+ rate. In addition, the higher K+ rates strengthened the translocation of organic nitrogenous compounds (amino acids) towards the fruit, thereby perhaps also enhancing the maximal commercial yield. In conclusion, for improved cucumber cultivation under greenhouse conditions, 0.15 mg ml−1 of K+ gave maximal yield, while the application of 0.30 mg ml−1 increased the metabolism and efficient utilisation of NO3−.
... It was observed that K + has a close relationship with NO 3 − -N uptake by roots and affects photosynthetic production, thus affecting the NO 3 − -N active absorption process (Wang et al., 2016b). Moreover, in the xylem, K is transported with NO 3 − -N together and affects NO 3 − -N distribution between roots and leaves (Ruiz and Romero, 2002;Hu et al., 2016). NH 4 + -N could affect root NO 3 − -N transport and thus play a main role in the regulation of N absorption by the crops (Nacry et al., 2013). ...
... K deficiency significantly increased AA and soluble protein in cotton leaves (Wang et al., 2012). In contrast, AA and protein were reduced in leaves of cucumber (Cucumis sativus) and corn (Zea mays L.) (Ruiz and Romero, 2002;Qu et al., 2011) or had an opposite trend in the subtending leaf to cotton boll (Hu et al., 2016). Under K deficiency, AA and protein differ between crop species and varieties. ...
... Oven-dried samples (roots and leaves) of 0.2 g were mixed with distilled water (10 mL) at 100°C for 1 h to analyze NO 3 − -N and NH 4 + -N. NO 3 − -N was measured using a salicylic acid method (Ruiz and Romero, 2002). NH 4 + -N was measured using a colorimetric method (Weatherburn, 1967;Xia et al., 2020). ...
In order to explore the effect of potassium (K) deficiency on nitrogen (N) metabolism in sweet potato ( Ipomoea batatas L.), a hydroponic experiment was conducted with two genotypes (Xushu 32, low-K-tolerant; Ningzishu 1, low-K-sensitive) under two K treatments (−K, <0.03 mM of K ⁺ ; +K, 5 mM of K ⁺ ) in the greenhouse of Jiangsu Normal University. The results showed that K deficiency decreased root, stem, and leaf biomass by 13%–58% and reduced whole plant biomass by 24%–35%. Compared to +K, the amount of K and K accumulation in sweet potato leaves and roots was significantly decreased by increasing root K ⁺ efflux in K-deficiency-treated plants. In addition, leaf K, N, ammonium nitrogen (NH 4 ⁺ –N), or nitrate nitrogen (NO 3 ⁻ –N) in leaves and roots significantly reduced under K deficiency, and leaf K content had a significant quadratic relationship with soluble protein, NO 3 ⁻ –N, or NH 4 ⁺ –N in leaves and roots. Under K deficiency, higher glutamate synthase (GOGAT) activity did not increase amino acid synthesis in roots; however, the range of variation in leaves was larger than that in roots with increased amino acid in roots, indicating that the transformation of amino acids into proteins in roots and the amino acid export from roots to leaves were not inhibited. K deficiency decreased the activity of nitrate reductase (NR) and nitrite reductase (NiR), even if the transcription level of NR and NiR increased, decreased, or remained unchanged. The NO 3 ⁻ /NH 4 ⁺ ratio in leaves and roots under K deficiency decreased, except in Ningzishu 1 leaves. These results indicated that for Ningzishu 1, more NO 3 ⁻ was stored under K deficiency in leaves, and the NR and NiR determined the response to K deficiency in leaves. Therefore, the resistance of NR and NiR activities to K deficiency may be a dominant factor that ameliorates the growth between Xushu 32 and Ningzishu 1 with different low-K sensitivities.
... No entanto, plantas de rabanete fertilizadas com N amoniacal apresentam menor quantidade de nitrato em comparação às supridas com fontes nítricas [13]. Além disso, trabalhos sugerem que o aumento na taxa de aplicação de potássio facilita a absorção e o transporte para a parte aérea da planta, promovendo o metabolismo e a utilização de nitrato [14,15]. ...
... Nas folhas, a redução de nitrato em nitrito seguida de redução de nitrito em amônio é catalisada respectivamente pelas enzimas, nitrato redutase e nitrito redutase [45]. Como a aplicação de K potencializa a atividade da RN, sua aplicação é desejável para reduzir os riscos à saúde relacionados à toxicidade do nitrato [11,15]. ...
... Estes resultados corroboram com os achados de Ahmed et al. (2000) [14] e Ruiz e Romero (2002) [15], que relataram que o aumento na taxa de aplicação de potássio facilita a absorção e o transporte de nitrato para a parte aérea da planta, promovendo o metabolismo e a utilização de nitrato. ...
Nitrogênio e potássio são os nutrientes mais extraídos e exportados pela cultura do rabanete, sendo imprescindíveis para a produtividade e qualidade das raízes produzidas. Desta forma, o presente estudo foi desenvolvido com o objetivo de avaliar alterações no crescimento de plantas e qualidade de raízes de rabanete em função de doses de potássio e fontes de nitrogênio. O experimento foi conduzido em delineamento inteiramente casualizado, com tratamentos arranjados em esquema fatorial 4 x 2, sendo quatro doses de potássio (K), 0, 70, 140 e 210 kg ha-1 de K2O e duas fontes de nitrogênio (N), sulfato de amônio e nitrato de cálcio, com quatro repetições. As plantas foram avaliadas quanto ao crescimento, rendimento, qualidade bioquímica das raízes e atividade da redutase do nitrato nas folhas. Os tratamentos não influenciaram as características de crescimento e rendimento: massa fresca de folhas, massa seca de folhas, área foliar total, comprimento e diâmetro de raiz. A adubação potássica aumentou o conteúdo de vitamina C nas raízes de rabanete e a atividade da redutase do nitrato nas folhas, principalmente quando a fonte de N utilizada foi o nitrato de cálcio. O maior valor de índice SPAD foi obtido na dose de 51 kg ha-1 de K2O. A utilização do sulfato de amônio propiciou maior teor de sólidos solúveis nas raízes.
... Some studies evaluated the relationship between K and N metabolism. In contrast to the antagonistic relationship between K + and NH 4 + nutrition, the acquisition rates of K + and NO 3 − are often found to be positively correlated (Rufty et al., 1981;Coskun et al., 2016), and sufficient K supply can promote N metabolism and enhance the synthesis of amino acids and proteins (Ruan et al., 1998;Ruiz and Romero, 2002). Hu et al. (2016b) found that K deficiency could reduce Nitrate reductase (NR), Glutamine synthetase (GS), and Glutamate synthase (GOGAT) activities and inhibit nitrate absorption in cotton, whereas Armengaud et al. (2009) found that K deficiency could up-regulate the activities of GS and Glu dehydrogenase (GDH) in Arabidopsis. ...
... As a result, a higher 15 N absorption content appeared under appropriate K supply conditions (Figure 8). In addition, K also affected the distribution of NO 3 − between root and shoot (Ruiz and Romero, 2002). Our results show that higher 15 N distribution ratio in roots were found in K deficient or excess treatments, while the highest 15 N distribution ratio in leaves appeared under appropriate K supply treatments. ...
... NO 3 − will be transformed into NH 4 + in plants, and NH 4 + will be converted mainly through the GS/GOGAT pathway. Thus the activity of NR and GS will affect the absorption and assimilation of N. The inhibition of K deficiency on NR activity has been verified in cotton, cucumber, and Arabidopsis (Ruiz and Romero, 2002;Balkos et al., 2010;Hu et al., 2016b). Generally, with high external K + supply, the co-translocation of K + and NO 3 − to the shoot increases (Ben Zioni et al., 1971;Blevins et al., 1978), and both storage of NO 3 − and NR activity increases in leaves, while less N assimilation is found in roots (Blevins et al., 1978;Rufty et al., 1981). ...
Nitrogen (N) is one of the most required mineral elements for plant growth, and potassium (K) plays a vital role in nitrogen metabolism, both elements being widely applied as fertilizers in agricultural production. However, the exact relationship between K and nitrogen use efficiency (NUE) remains unclear. Apple dwarf rootstock seedlings (M9T337) were used to study the impacts of different K levels on plant growth, nitrogen metabolism, and carbon (C) assimilation in water culture experiments for 2 years. The results showed that both deficiency and excess K inhibited the growth and root development of M9T337 seedlings. When the K supply concentration was 0 mM and 12 mM, the biomass of each organ, root-shoot ratio, root activity and NO3– ion flow rate decreased significantly, net photosynthetic rate (Pn) and photochemical efficiency (Fv/Fm) being lower. Meanwhile, seedlings treated with 6 mM K+ had higher N and C metabolizing enzyme activities and higher nitrate transporter gene expression levels (NRT1.1; NRT2.1). 13C and 15N labeling results showed that deficiency and excess K could not only reduce 15N absorption and 13C assimilation accumulation of M9T337 seedlings, but also reduced the 15N distribution ratio in leaves and 13C distribution ratio in roots. These results suggest that appropriate K supply (6 mM) was optimal as it enhanced photoassimilate transport from leaves to roots and increased NUE by influencing photosynthesis, C and N metabolizing enzyme activities, nitrate assimilation gene activities, and nitrate transport.
... Free amino acid and soluble protein contents. Free amino acids were first extracted using the method of Ruiz and Romero [2002]. Briefly, a 0.5 g fresh leaf sample was crushed in 5 mL of cold phosphate buffer (50 mM KH 2 PO 4 , pH 7), and centrifuged at 12,000 × g for 15 min. ...
... This is a possible explanation for the reduction in growth characters and yield under K deficiency (T1) (Tables 1 and 2). Ruiz and Romero [2002], Salim et al. [2014] and Hu et al. [2016] reported similar reductions in free amino acid content and increases in protein content as a result of K application. Our results suggest that the distribution of nitrogenous compounds (between amino acids and protein) and their transformation changed due to K supply. ...
... Among primary nutrients, potassium plays significant role in plant growth and development as well as in product quality attributes (Tohidloo, Souri, and Eskandarpour 2018;Mardanluo, Souri, and Ahmadi 2018). It is also associated with carbon assimilation, sugar translocation, nitrogen assimilation, stomatal conductance, cell elongation, enzyme activation and other important physiological processes (Ruiz and Romero 2002;Oosterhuis et al. 2014). Potassium is highly mobile in plant system and involves in the regulation of cell osmotic pressure and ionic exchange (Hu et al. 2016). ...
... Potassium also influences ascorbic acid content and accumulation of soluble carbohydrates (Lester, Jifon, and Rogers 2005;Malvi 2011). Increase in protein content could be attributed to the involvement of potassium in biosynthesis of enzymes, amino acids and proteins during fruit development (Ruiz and Romero 2002). The bioactive compounds of fruits such as betacyanin (pulp pigment), phenol, flavonoid and FRAP activity also increased with K application ( Table 6). ...
Production of quality fruits has always been the priority for ensuring better nutrition and market value. Considering the role of potassium in fruit quality improvement a study was carried out in dragon fruit under open field condition during 2020 and 2021 in the eastern tropical climatic condition of India. The treatments comprised viz., K-absentia as control (T1), K 50 g hill−1 year⁻¹ (T2), K 100 g hill−1 year⁻¹ (T3), K 200 g hill−1 year⁻¹ (T4), K 300 g hill−1 year⁻¹ (T5), K 400 g hill−1 year⁻¹ (T6) and K 500 g hill−1 year⁻¹ (T7). Application of K @300 g hill−1 year⁻¹ exhibited the maximal acquisition of minerals such as N, P, K, Mg, Fe, Mn, Zn, Cu in shoot and fruit pulp of dragon fruit. However, calcium did not exhibit a discernible trend. However, excessive dose of K (500 g hill⁻¹year⁻¹) resulted in declination in mineral acquisition. K 300 g hill−1 year⁻¹ (T5) also demonstrated enhanced absolute fruit growth rate, maximal yield, marketable yield, fruit weight, color attributes, bio-chemical attributes such as TSS, carbohydrate, reducing sugar (∼20%), protein, citric acid, ascorbic acid content (∼2 times). Additionally, the same treatment also manifested an enhancement in biochemical attributes such as betacyanin (∼2.2 times), total phenol (∼55%), total flavonoid (∼2.7 times), α-amylase and sucrose synthase activities, and antioxidative property (FRAP activity). Principal component analysis (PCA) illustrated the maximal proximity of most of the variables (quality attributes and mineral nutrient contents) with T5 (K 300 g hill−1 year⁻¹), exemplifying it as the best representative of all the studied variables.
... Free amino acid and soluble protein contents. Free amino acids were first extracted using the method of Ruiz and Romero [2002]. Briefly, a 0.5 g fresh leaf sample was crushed in 5 mL of cold phosphate buffer (50 mM KH 2 PO 4 , pH 7), and centrifuged at 12,000 × g for 15 min. ...
... This is a possible explanation for the reduction in growth characters and yield under K deficiency (T1) (Tables 1 and 2). Ruiz and Romero [2002], Salim et al. [2014] and Hu et al. [2016] reported similar reductions in free amino acid content and increases in protein content as a result of K application. Our results suggest that the distribution of nitrogenous compounds (between amino acids and protein) and their transformation changed due to K supply. ...
Potassium (K) levels are decreasing worldwide in agricultural soils, and K deficiency is becoming a major issue.
Study on damask rose response to K application is scarce. Furthermore, despite its importance in the cell
division, photosynthesis and protein synthesis, there is a lack of published reports on plant responses to zinc
(Zn) application. Further research is required to understand the damask rose’s response to both elements. This
study investigated the effects of K and Zn foliar application on the vegetative growth, flower yield, and volatile
oil content and composition of damask rose. K and Zn nutrition was applied either individually or combined
as K2SO4 and ZnSO4 at 0.5 or 1.0%. Foliar application of K2SO4 and ZnSO4 was applied with a manual
pump four times in each growing season, the first at the beginning of stem elongation and leaf formation, and
then at two-weekly intervals. Results showed that K and/or Zn treatments significantly improved the growth
characters, flower yield, relative water content (RWC), stomatal conductance, and essential oil content and
composition such as linalool, nerol, citronellol, geraniol, and nonadecane. The chlorophyll content, total soluble
sugars (TSS), and protein content also increased, but free amino acid content decreased, suggesting that
the distribution of nitrogenous compounds (between amino acids and proteins) and their transformation were
influenced by K and Zn supply. Individual applications of K or Zn increased the N, P, K, and Zn contents in
damask rose leaves, relative to the control, which increased further with combined applications of K and Zn.
Results suggest that foliar application of K and/or Zn could be part of the damask rose fertilization program
to provide plants with the optimum level of nutrition for improving the quantity and quality of flowers and
essential oil yields.
... Free amino acid and soluble protein contents. Free amino acids were first extracted using the method of Ruiz and Romero [2002]. Briefly, a 0.5 g fresh leaf sample was crushed in 5 mL of cold phosphate buffer (50 mM KH 2 PO 4 , pH 7), and centrifuged at 12,000 × g for 15 min. ...
... This is a possible explanation for the reduction in growth characters and yield under K deficiency (T1) (Tables 1 and 2). Ruiz and Romero [2002], Salim et al. [2014] and Hu et al. [2016] reported similar reductions in free amino acid content and increases in protein content as a result of K application. Our results suggest that the distribution of nitrogenous compounds (between amino acids and protein) and their transformation changed due to K supply. ...
Potassium (K) levels are decreasing worldwide in agricultural soils, and K deficiency is becoming a major issue. Study on damask rose response to K application is scarce. Furthermore, despite its importance in the cell division, photosynthesis and protein synthesis, there is a lack of published reports on plant responses to zinc (Zn) application. Further research is required to understand the damask rose's response to both elements. This study investigated the effects of K and Zn foliar application on the vegetative growth, flower yield, and volatile oil content and composition of damask rose. K and Zn nutrition was applied either individually or combined as K2SO4 and ZnSO4 at 0.5 or 1.0%. Foliar application of K2SO4 and ZnSO4 was applied with a manual pump four times in each growing season, the first at the beginning of stem elongation and leaf formation, and then at two-weekly intervals. Results showed that K and/or Zn treatments significantly improved the growth characters, flower yield, relative water content (RWC), stomatal conductance, and essential oil content and composition such as linalool, nerol, citronellol, geraniol, and nonadecane. The chlorophyll content, total soluble sugars (TSS), and protein content also increased, but free amino acid content decreased, suggesting that the distribution of nitrogenous compounds (between amino acids and proteins) and their transformation were influenced by K and Zn supply. Individual applications of K or Zn increased the N, P, K, and Zn contents in damask rose leaves, relative to the control, which increased further with combined applications of K and Zn. Results suggest that foliar application of K and/or Zn could be part of the damask rose fertilization program to provide plants with the optimum level of nutrition for improving the quantity and quality of flowers and essential oil yields.
... In recent decades, nitrate applied as a nitrogen source has been realized to frequently accumulate in leafy vegetables, yet controlling its accumulation has proved challenging (Santamaria et al., 2001). Various nutritional approaches have been suggested to reduce nitrate accumulation in lettuce, including ending the crop N supply some few days before harvesting (Santamaria et al., 2001), replacing nitrate N with chloride or sulphate a few days prior to harvesting (Inal & Tarakcioglu, 2001), and increasing the potassium concentration in the nutrient solution (Ruiz & Romero, 2002). However, these methods have been utilized with varying success. ...
... Some earlier studies have also shown potassium applications to have little effect in reducing nitrate accumulation in plants (Drlik & Rogl, 1992). In contrast, potassium application may reportedly increase the uptake and transport of nitrates to the shoots, thus promoting the metabolism and utilization of nitrate, resulting in reduced nitrate accumulation in the leaves (Ruiz & Romero, 2002). ...
Leafy vegetables like lettuce (Lactuca sativa L.) naturally have high nitrate content and the European Commission has set maximum level for nitrate in lettuce. Glycinebetaine is an organic osmolyte alleviating plant stress, but its role in leaf nitrate accumulation remains unknown. The uptake of glycinebetaine by lettuce roots, and its potential to regulate lettuce nitrate content and improve plant quality were investigated. Two hydroponic lettuce experiments were conducted with different glycinebetaine application rates (Exp1: 0, 1, 7.5, and 15 mM; Exp2: 0, 1+1+1, 1+10, and 4 mM). Plants were analyzed at varying time points. Root application resulted in glycinebetaine uptake and translocation to the leaves. Glycinebetaine concentrations >7.5 mM reduced leaf nitrate up to 40% and increased leaf dry matter content. Glycinebetaine showed a positive effect on leaf mineral and amino acid composition. Thus, glycinebetaine could be a novel strategy to reduce the nitrate content in hydroponic lettuce.
... Balanced K nutrition is indispensable for uptake of other essential nutrients from the soil, transportation to the areal part, and ultimate use in metabolism. Nitrate in the xylem sap, for example, moves along with the K ion (Dong et al., 2012) and is disseminated into different plant parts (Ruiz and Romero, 2002) with an adequate K supply. Similarly, amino acids synthesis and protein formation in cotton leaves are strictly K dependent, and K deficiency at a particular crop stage leads to an imbalance in the amino acids (Wang et al., 2012), which impairs protein synthesis as well as amino acids transportation to other parts of the plant. ...
... understanding to dependency on K availability. These results were also supported by previous findings on cucumber (Cucumis sativus L.) (Ruiz and Romero, 2002), barley (Hordeum vulgare L.) (Blevins, 1985), and cotton (Hu et al., 2016;Zahoor et al., 2017), where K application evidently enhanced NR activity. The enzymes (GS and GOGAT) work side by side for amino acids synthesis. ...
2: 1)] were applied in a randomized complete block design, in 2016 and 2017. Results revealed that increasing the K fertilization ratio exerted a significant effect on leaf area, fresh and dry weight of functional leaf, chlorophyll content, and N metabolism, as well as yield and yield indices in both cropping years. Higher lint yield was obtained with the application of K 2 and K 3 rather than K 1. Similarly, K 2 and K 3 treatments evidently improved the activity of N metabolizing enzymes such as NR (nitrate reductase), NiR (nitrite reductase), GS (glutamine synthetase), GOGAT (glutamate synthase), GPT (glutamic-pyruvic transaminase), and GOT (glutamic oxaloacetic transaminase). Moreover, leaf nitrogen, nitrate-N, free amino acids, and soluble protein contents were efficiently balanced in K 2 and K 3 treatments over K 1. The findings of this study suggest that the application of K ratio must be equivalent to N to achieve an acceptable yield and profitable return in late-planted high-density cotton.
... Balanced K nutrition is indispensable for uptake of other essential nutrients from the soil, transportation to the areal part, and ultimate use in metabolism. Nitrate in the xylem sap, for example, moves along with the K ion (Dong et al., 2012) and is disseminated into different plant parts (Ruiz and Romero, 2002) with an adequate K supply. Similarly, amino acids synthesis and protein formation in cotton leaves are strictly K dependent, and K deficiency at a particular crop stage leads to an imbalance in the amino acids (Wang et al., 2012), which impairs protein synthesis as well as amino acids transportation to other parts of the plant. ...
... understanding to dependency on K availability. These results were also supported by previous findings on cucumber (Cucumis sativus L.) (Ruiz and Romero, 2002), barley (Hordeum vulgare L.) (Blevins, 1985), and cotton (Hu et al., 2016;Zahoor et al., 2017), where K application evidently enhanced NR activity. The enzymes (GS and GOGAT) work side by side for amino acids synthesis. ...
2: 1)] were applied in a randomized complete block design, in 2016 and 2017. Results revealed that increasing the K fertilization ratio exerted a significant effect on leaf area, fresh and dry weight of functional leaf, chlorophyll content, and N metabolism, as well as yield and yield indices in both cropping years. Higher lint yield was obtained with the application of K 2 and K 3 rather than K 1. Similarly, K 2 and K 3 treatments evidently improved the activity of N metabolizing enzymes such as NR (nitrate reductase), NiR (nitrite reductase), GS (glutamine synthetase), GOGAT (glutamate synthase), GPT (glutamic-pyruvic transaminase), and GOT (glutamic oxaloacetic transaminase). Moreover, leaf nitrogen, nitrate-N, free amino acids, and soluble protein contents were efficiently balanced in K 2 and K 3 treatments over K 1. The findings of this study suggest that the application of K ratio must be equivalent to N to achieve an acceptable yield and profitable return in late-planted high-density cotton.
... Zhang et al. [3] reported that rapid nitrate uptake depends upon adequate K in the soil solution. The significance of potassium in affecting the uptake, translocation and reduction of NO 3 − is well documented by Ruiz and Romero [22]. Shrotriya [23] reported that balanced application of N, P and K might cause up to 122% increase in sorghum yield in India. ...
... This study as indicated in Figures 5 and 6 also suggests that potassium application reduced the nitrate accumulation in leaves, which is in accordance with the findings of Ahmed et al. [48] and Ruiz and Romero [22]. They reported that increase in the rate of potassium application facilitated the uptake and transport of nitrate towards the aerial parts of the plant, promoted the metabolism and utilization of nitrate and ultimately, reduced the nitrate accumulation in plants. ...
... Through these processes, K is involved in regulating stomatal opening, cell elongation, and other important physiological processes. Also adequate K supply can promote N metabolism and enhance the synthesis of amino acids and proteins (Ruan et al., 1998;Ruiz and Romero, 2002). Also, PBZ influences the isoprenoid pathway and changes the status of phytohormones by inhibiting gibberellin synthesis, decreasing ethylene production, and enhancing cytokinin and ABA contents (Kamountsis and Sereli 1999). ...
A field trial was led at the Centre of Date Palm Researches, Basrah University, to investigate the effect of Paclobutrazol) PBZ) at 0, 100 and 200 mg. L-1 and Potassium Sulfate)K 2 SO 4) at 0, 2.5, and 5 g. L-1 on growth characteristics of Phoenix dactylifera L. plants grown from seeds in a factorial experiment designed with R.C.B.D. Most growth parameters recorded were affected by the application of Paclobutrazol and/ or potassium sulfate. Results showed a significant decrease in the number of leaves, leaf length, leaf width, leaf area, and shoot height when applying PBZ. In contrast, shoot dry weight, root length, and root dry weight was increased. Whereas the application of Potassium significantly improved all the previous parameters. On the other hand, total chlorophyll content, dry matter, total soluble carbohydrates, protein content, potassium content in leaves, and C/N ratio in leaves showed a significant increase in PBZ and K 2 SO 4 treatments. The interaction between the two factors in this trial was found significantly effective in some growth parameters.
... The largest K concentration was measured in the leaves and stems, but it was almost absent in the roots [31]. The interaction between K and N is an important determinant of plant growth; K can promote N metabolism and enhance the synthesis of amino acids and proteins [32]. Sodium (Na) was also highly represented in the aboveground tissues of L. discolor. ...
Ludisia discolor is commonly known as a jewel orchid due to its variegated leaves. Easy maintenance of the orchid allows it to be used as a test system for various fertilizers and nutrient sources, including aquaponic water (AW). First, we applied DNA barcoding to assess the taxonomic identity of this terrestrial orchid and to construct phylogenetic trees. Next, the vegetative organs (leaf, stem, and root) were compared in terms of the level of metabolites (reducing sugars, proteins, anthocyanins, plastid pigments, phenolics, and antioxidant activity) and nutrient elements (carbon, nitrogen, sodium, and potassium), which highlighted the leaves as most functionally active organ. Subsequently, AW was used as a natural source of fish-derived nutrients, and the orchid growth was tested in hydroponics, in irrigated soil, and in an aquaponic system. Plant physiological status was evaluated by analyzing leaf anatomy and measuring chlorophyll content and chlorophyll fluorescence parameters. These results provided evidence of the beneficial effects of AW on the jewel orchid, including increased leaf formation, enhanced chlorophyll content and photosystems’ productivity, and stimulated and prolonged flowering. The information acquired in the present study could be used in addressing additional aspects of the growth and development of the jewel orchid, which is also known for its medicinal value.
... Artificial fertilizers with a base of ammonia or a mixture of nitrate and ammonium when applied to the soil can affect the nitrate content in plants (Inal and Tarakcioglu, 2001;Santamaria et al., 2001) Nutrient balance plays an important role in affecting the nutrient status of plants (Ahmed et al., 2000). Increase rate of potassium when applied allows the uptake and transportation of nitrate towards leaves and apex of the plant facilitates the metabolism and utilization of nitrate thereby reducing nitrate accumulation in some vegetable crops (Ahmed et al., 2000;Zhou et al., 2000;Ruiz and Romero, 2002). Application of other nutrients such as salicylic acid, molybdenum, and calcium through leaves can reduce the nitrate content of plants (Xu et al., 2005;Tzung et al., 1995). ...
... Balanced N nutrition allows plants to absorb other essential nutrients from the soil and transport them to other tissues to ultimately act on the metabolic network. For example, nitrates in the xylem of wheat move together with potassium ions and diffuse into speci c tissues 10,11 , Earlier studies have found that the accumulation of amino acids and proteins in C. tinctoria leaves depends heavily on the N concentration. When plants are under low N stress, protein synthesis and amino acid transport systems are hindered 12 . ...
Coreopsis tinctoria , as a medicinal plant, has become popular in China in the past decade. However, basic data on NO 3 ⁻ supply related to its production and nitrogen (N) metabolism are lacking. In this study, all plants were grown to four leaves in substrate (vermiculite:perlite = 2:1), which were subsequently transferred to different reducing NO 3 ⁻ solutions. Appropriate N fertilizer application reductions (1/8N-1/2N) maintained the flower number and biomass of Coreopsis tinctoria during 2020–2021. N fertilizer reduction maintained the N assimilation levels of C. tinctoria and increased N use efficiency (NUE), one of the important reasons was that the reduction of N fertilizer did not damage the chlorophyll fluorescence system and photosynthetic system. 1/2N-1/8N treatment also maintained the activities nitrate reductase (NR), nitrite reductase (NIR), glutamine synthase (GS) and glutamate synthase (GOGAT) and the content of total amino acid and soluble protein in leaves. N reduction treatment also increased the levels of tyrosine (Thr), serine (Ser), leucine (Leu), isoleucine (Ile), lysine (Lys) and arginine (Arg) of leaves in C. tinctoria , and further enhances N assimilation ability. Leaf N content was significantly correlated with the activities of NR, NIR, GS, GOGAT and GDH, indicating that N metabolism was effectively regulated by N levels. In conclusion, the 1/8 N level prior to harvest could be one of the strategies for C. tinctoria cultivation because it minimizes planting costs and maintains nitrogen assimilation capacity and productivity.
... Similar increases in protein content of forage sorghum and maize due to foliar spray of urea (Kheirabadi et al., 2012) support the increases in N concentration of forage sorghum. Ruiz and Romero (2002) reported that increase in the rate of potassium application facilitated the uptake and transport of nitrate towards the aerial parts of the plant, promoted the metabolism and utilization of nitrate and ultimately, reduced the nitrate accumulation in plants. Shrotriya (1998) reported that balanced application of N, P and K might cause up to 122% increase in sorghum yield in India. ...
A field experiment was conducted during 2019 and 2020 to evaluate the effect of plant bio-regulators on forage productivity and quality of sorghum grown as rainfed crop. Foliar application of plant bio-regulators included 2% urea, 2% NPK (18-18-18), 2% potassium nitrate (KNO3), 1 and 2 ppm silicic acid and 100 ppm salicylic acid at panicle initiation and flag leaf emergence stage compared with no spray as well as water spray. The application of PBRs increased green fodder yield by 7.4–22.4% over control. On pooled mean basis, the highest green and dry fodder yield of 68.35 and 20.54 t/ha, respectively was recorded with application of 2% KNO3. Application of urea and KNO3 recorded significantly higher crude protein content of the fodder over other foliar sprays. Besides, there was substantial reduction in the HCN content due to KNO3 spray over control. Foliar application of KNO3 presents a viable option for improving sorghum fodder productivity and its quality under rainfed situation.
... ha-1 for traditional CORNE 1 variety. Nitrogen uptake is a function of potassium [37,38,39] and the correlation that allows for a good fruit characteristic is a function of variety [40,41,42]. Fruits in the T5 treatment were more acidic during ripening compared to those of T2 treatment while fruits in the T2 and T4 treatments recorded the highest pH. ...
This study was undertaken to measure the impact of fertilizers (nitrogen-potassium) on plantain fruits during ripening. Based on nitrogen and potassium content, different doses of fertilizers (T2, T3, T4, T5 and T6) were applied to two hybrid varieties (PITA 3 and FHIA 21) and a traditional variety (CORNE 1) on an experimental split plot plan with a planting density of 2500 plants per hectare. Results showed that total soluble solids (from 0.1° to 1.9 – hybrids and 2.14 – CORNE 1) and moisture content (PITA 3: 67.64 ± 0.06% – 74.63 ± 1.02%; FHIA 21: 67.81 ± 0.89% – 72.19 ± 2.10% and CORNE 1: 61.71 ± 0.23% - 67.78 ± 1.11%) increased significantly during ripening, while firmness (33.93 ± 1.00 N – 1.78 ± 0.76 N), pH (22.90 ± 1.01% - 24.18 ± 2.00%) and hue angle values for peel (27.03% - 31.02%) and pulp (0.05% - 3.66%) decreased considerably. Fruit grown without fertilizer T1 had the lowest moisture (PITA 3: 65.07 ± 1.09% - 68.08 ± 2.00%; FHIA 21: 65.35 ± 3.09% - 69.95 ± 0.09% and CORNE 1: 59.00 ± 1.23% - 65.15 ± 0.67%) content and firmness reducing (72.83 ± 0.24% PITA 3 and 79.49 ± 1.87% CORNE 1). In contrast, PITA 3 (92.14 ± 2.01%) and CORNE 1 (86.84 ± 1.03%) fruits from T4 treatment with high nitrogen content (360 kg/ha) had the highest firmness drop at yellow stage of ripening. Firmness of hybrid PITA 3 and FHIA 21 yellow fruits were twice (3.22 ± 0.03 N; 3.08 ± 0.12 N) smaller than CORNE 1 fruits (7.74 ± 1.02 N). The CORNE 1 fruits were the least humid and the firmer.
... It is well known that the uptake and transport of NO 3 − is largely determined by nitrate transporters (NRT) and the NO 3 − can be further transported and utilized by the catalysis of a series of N-metabolizing enzymes (Teng et al., 2017;Morales de Los Rios et al., 2021). K promoted the activities of nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT) and other nitrogen metabolism enzymes, which were verified in cotton (Hu et al., 2016) and cucumber (Ruiz and Romero, 2002). K can provide energy and facilitate N assimilation by increasing photosynthetic C metabolism, promoting protein synthesis and improving NUE (Hu et al., 2017). ...
Potassium (K) is an indispensable nutrient element in the development of fruit trees in terms of yield and quality. It is unclear how a stable or unstable supply of K affects plant growth. We studied the root morphology and physiological and molecular changes in the carbon and nitrogen metabolism of M9T337 apple rootstock under different K levels and supply methods using hydroponics. Five K supply treatments were implemented: continuous low K (K L ), initial low and then high K (K LH ), appropriate and constant K (K AC ), initial high and then low K (K HL ), and continuous high K (K H ). The results showed that the biomass, root activity, photosynthesis, and carbon and nitrogen metabolism of the M9T337 rootstocks were inhibited under K L , K H , K LH and K HL conditions. The K AC treatment promoted root growth by optimizing endogenous hormone content, enhancing carbon and nitrogen metabolism enzyme activities, improving photosynthesis, optimizing the distribution of carbon and nitrogen, and upregulating the transcription levels of nitrogen assimilation-related genes (nitrate reductase, glutamine synthetase, glutamate synthase, MdNRT1.1, MdNRT1.2, MdNRT1.5, MdNRT2.4 ). These results suggest that an appropriate and constant K supply ensures the efficient assimilation and utilization of nitrogen and carbon.
... Generally, K supply promotes the incorporation of N into proteins leading to higher levels of proteins and lower concentrations of amino acids in K-sufficient plants (in cotton (Hu et al., 2016b), in tobacco (Koch & Mengel, 1974), in rice (Mengel et al., 1976) and in barley (Helal & Mengel, 1979)). However, an increase of both protein and amino acid levels with increased K supply was found for tea leaves (Ruan et al., 1998) and cucumber (Ruiz & Romero, 2002), while in several other studies, no effect of K on protein and/or amino acid levels was detected (Amtmann & Rubio, 2001). Moreover, K deficiency increases the content in several free amino acids in oil palm (Ollagnier & Ochs, 1973) as well as Arabidopsis (Armengaud et al., 2009). ...
Oil palm (Elaeis guineensis Jacq.) is one of the most productive oil crop in the world. Unfortunately, positive effect of K fertilization on fruit development with increasing in bunch weight and number, remain rather difficult to predict because of the lack of knowledge of underlying metabolic mechanisms. The objective of this thesis was precisely to assess the effect of K availability on oil palm metabolic pathways and determine if metabolic changes could be related to oil production. In addition to expected effects of potassium on vegetative traits and bunches, our results show that K availability affected carbon and nitrogen primary metabolism in both leaflets and developing fruits.This thesis presents, for the first time, a detailed metabolic exploration of oil palm in the field and shows that some metabolic traits (metabolites or enzymes) are linked to K availability, thereby opening avenues for the use of leaf biochemical markers to monitor oil palm mineral nutrition.
... می (Ahmed et al., 2000;Ruiz and Romero, 2002) . این، وجود با تاثیر خاک پتاسیم منابع که است شده مشخص مطالعات از بعضی در بر ی ندارد نیترات تجمع میزان روی (Drlik and Rogl, 1992) . ...
Unbalanced application of nitrogen fertilizers disrupts the balance of nutrients in soils, changes the abundance and biodiversity of soil microorganisms, destroys the relationships between soil living components, interferes with natural cycles of nutrients, and reduces soil fertility which ultimately culminates in increasing demand and further use of chemical fertilizers. Moreover, the high solubility of nitrogen fertilizers and lack of attention to the required amount, right time, and right place in their application, threatens the health of groundwater aquifers and drinking water sources. In addition, due to the unbalanced and excessive use of nitrogen fertilizers, nitrate may accumulate in plant organs, thus entering the digestive systems of humans and animals. Within living organisms, nitrate is converted to the carcinogen compound, nitrosamine, which can cause cancer of the upper gastrointestinal tract. Considering the prevailing climatic conditions and soil characteristics of arable lands in Iran, the lack of nitrogen in the arable soils of Iran is regarded as one of the main limiting factors affecting the growth of agricultural plants. The purpose of this article is to study the factors affecting nitrate accumulation in crops, which include nutritional, environmental, and physiological factors along with economic, cultural, social, and political factors, and further provide on-farm management strategies and suggest stronger policies and extension strategies regarding efficient management of nutrient in agricultural soils. The following study also discusses the necessity of developing a balanced fertilization program for crops, the importance of replacing ammonium fertilizers and slow-release fertilizers with conventional N sources, considering foliar application, growing plants under controlled environmental conditions, and making informed decisions between genotypes and cultivars that accumulate less nitrate. Modification of new cultivars, the importance of harvest time, effect of moisture stress, climatic conditions (including temperature and light intensity), appropriate plant density, suitable planting time, and the important relationship between nitrate concentration and nitrate reductase activity in reducing nitrate accumulation in various products are also examined.(Full text of the paper is in the Persian language)
... To determine the free amino acids and total protein content, the method of Ruiz & Romero (2002) was used. Briefly, a fresh leaf sample (0.5gm) was crushed in 5mL cold phosphate buffer (50mM KH 2 PO 4 , pH 7), and centrifuged at 12000 xg for 15min. ...
... NO3 --N and NH4 + -N were extracted with distilled water (10 mL) from oven-dried samples (0.2 g) at 100 °C for 1 h to analyze NO3 --N and NH4 + -N. For NO3 --N measurement, a 0.1 mL aliquot was taken and added to 5% salicylic acid-sulfuric acid (w/v), the absorption values were measured using a microplate reader at 410 nm [43]. For NH4 + -N measurement, a 0.2 mL aliquot was taken and added to 1 mL reaction solution (2.625 g sodium hydroxide and 1.5 mL hypochlorous acid to a constant volume to 50 mL) and 1 mL chromogenic solution (12.5 mg sodium nitrite and 3 g phenol to constant volume to 50 mL), and then was placed in a water bath at 37 °C for 30 min [44]. ...
This study investigated the effect of water stress, simulated by the polyethylene glycol (PEG-6000) method, on nitrogen (N) metabolism in leaves and roots of hydroponically grown sweet potato seedlings, Xushu 32 (X32) and Ningzishu 1 (N1). The concentrations of PEG-6000 treatments were 0%, 5% and 10% (m/v). The results showed that the drought-treated plants showed a decline leaf relative water content, and revealed severe growth inhibition, compared with the 0% treatment. Under drought stress, the decline in biomass of the leaf and stem was more noticeable than in root biomass for X32, leading to a higher root to shoot ratio. Drought stress increased the nitrate nitrogen (NO3 −-N) and protein in leaves, but reduced all the activities of N-metabolism enzymes and the transcriptional levels of nitrate reductase (NR), glutamine synthetase (GS) and glutamate synthase (GOGAT); in roots, NO3 −-N and NR had opposite trends. The leaf ammonium nitrogen (NH4 +-N), GS and amino acid had different trends between X32 and N1 under drought stress. Furthermore, the transcriptional level of nitrate transporter genes NRT1.1 in leaves and roots were upregulated under drought stress, except in N1 roots. In conclusion, NR determined the different response to drought in leaves for X32 and N1, and GS and GOGAT determined the response to drought in roots, respectively.
... Vegetables, in fact, are generally rich in K; higher levels are present in leafy vegetables such as spinach (5580 mg/kg of fresh weight) and Swiss chard (3790 mg/kg of fresh weight) [11,12] This element constitutes up to 10% of plant dry weight and is considered a macronutrient essential for plants, with fundamental effects on their health, growth, and development [13]. As a result, it is difficult to reduce the physiological K concentration in plants without having detrimental effects on yield and marketable quality, because of the fundamental physiological functions of K, including enzyme activation, osmotic regulation, photosynthesis, and translocation of the products of photosynthesis [14,15]. Recently, Renna et al. (2018) [16] reported reduction of K tissue concentration in microgreens of two cultivars of chicory (Cichorium intybus L.) and one cultivar of lettuce (Lactuca sativa L. group crispa). ...
Tailored foods are specifically suitable for target groups of people with particular nutritional needs. Although most research on tailored foods has been focused on increasing the nutrient content in plant tissues (biofortification), in populations with specific physiological conditions, it is recommended to reduce the uptake of specific nutrients in order to improve their health. People affected by chronic kidney disease (CKD) must limit their consumption of vegetables because of the generally high potassium (K) content in the edible parts. This study aimed to define an appropriate production technique for two baby leaf vegetables, spinach (Spinacia oleracea L.) and Swiss chard (Beta vulgaris L. ssp. vulgaris), with reduced K tissue content, minimizing the negative effects on their crop performance and overall nutritional quality. Plants were grown in a hydroponic floating system. The K concentration in the nutrient solution (NS) was reduced from 200 mg/L (K200, the concentration usually used for growing baby leaf vegetables in hydroponic conditions) to 50 mg/L over the entire growing cycle (K50) or only during the seven days before harvest (K50-7d). The reduction of K in the NS resulted in a significant decrease of K tissue content in both species (32% for K50 and 10% for K50-7d, on average), while it did not, in general, compromise the crop performance and quality traits or the bioaccessibility of K, magnesium, and calcium. The production of reduced-potassium leafy vegetables is a feasible tailored nutrition approach for CKD patients in order to take advantage of the positive effects of vegetable consumption on health without excessively increasing potassium intake.
... Potassium concentrations differed only slightly among the varieties of lettuce. Although not tested here, K had a positive effect on accumulation and reduction of nitrate in leaves of cucumber (Ruiz and Romero 2002). Calcium in tissues was statistically equal in HOAG or OF solution; however, Arroyo, Buttercrunch, and Caretaker had statistically equal C concentrations that were higher than in Bergam's Green. ...
The objective of this experiment was to assess the effects of organic or chemical nutrient solutions on the growth and composition of lettuce (Lactuca sativa L.) in greenhouse production. Hoagland and Arnon nutrient solution, an organic hydroponics solution, and no fertilization were factored with lettuce cultivars of different phenotypes, iceberg, romaine, loose head, and loose leaf. Lettuce growth was higher with Hoagland and Arnon solution than with the organic fertilizer or with no fertilization. The organic fertilizer increased growth above no fertilizer applied. Hoagland and Arnon solution gave the highest concentration of nitrogen, potassium, magnesium, and iron in the lettuce whereas lettuce grown with the organic fertilizer had the highest phosphorus. Plant nutrient accumulation differed slightly among the cultivars. Hoagland and Arnon solution produced high nitrate in leaves. Nitrate concentrations with organic or no fertilization were low. Loose head or loose leaf cultivars had higher nitrate than romaine or iceberg.
... However, N and K have been reported as more important nutrients regarding NR activity (Marschner 2011). In cucumber leaves it has been shown that increasing K levels improved NR activity (Ruiz and Romero 2002). Also an increase in NR activity by external factors such as N application has been reported (Marschner 2011;Sivasankar and Oaks 1996). ...
A nutrient solution experiment was done to evaluate effects of different concentrations of nitrogen (N), phosphorus (P) and potassium (K) on leaf mineral concentrations and some enzymes activity of melon seedlings (Cucumismelo var. inodorus subvar. Khatouni). Different levels of these nutrients including 0, 53, 105, 158 and 210 mg L⁻¹ N; 0, 8, 16, 23 and 31 mg L⁻¹ P; 0, 59, 118, 176 and 235 mg L⁻¹ K, all corresponding to 0, 25, 50, 75 and 100% of their concentrations in Hoagland nutrient solution, were applied to plants. The results showed that the highest leaf nitrate reductase (NR) activity was observed at highest N and P levels, whereas the three highest K levels showed the highest NR activity. The highest leaf peroxidase activity was observed at 8 mg L⁻¹ P, 59 mg L⁻¹ K and 158 mg L⁻¹ N. The leaf catalase activity was highest at zero concentration of P, 158 mg L⁻¹ N and 176 mg L⁻¹ K; however, catalase activity was decreased by increasing P levels. Leaf protein content showed an increasing trend with increasing N, P and K levels of nutrient solution, while there was no significant difference between 158 and 210 mg L⁻¹ N. The highest leaf concentrations of N, P, K and Mg were observed at highest nitrogen, potassium and phosphorus levels of nutrient solution, whereas the highest leaf concentration of Ca were obtained at 53 or 105 mg L⁻¹ N, 176 mg L⁻¹ K and 23–31 mg L⁻¹ P. The highest iron concentration of leaves was obtained from 23 to 31 mg L⁻¹ P, 176 mg L⁻¹ K and 210 mg L⁻¹ N.
... This might be due to nitrate reductase enzyme activity which increased with plant age and thus decreased the nitrate content. These results are in accordance with the findings of Ahmed et al., (2000) and Ruiz and Romero (2002). ...
... A 100-μl aliquot was taken for NO 3 − determination and added to 10% (w/v) salicylic acid in H 2 SO 4 at 96%. The absorbance of the solution was measured at A410 nm according to Ruiz and Romero (2002), and NO 3 − content was expressed in mg g −1 DW. Leaf total N content was assayed following the H 2 SO 4 -H 2 O 2 Kjeldhal digestion method. ...
Short-term waterlogging and chronic elevated temperature occur frequently in the Yangtze River Valley, yet the effects of these co-occurring environments on nitrogen metabolism of the subtending leaf (a major source leaf for boll development) have received little attention. In this study, plants were exposed to two temperature regimes (31.6/26.5 °C and 34.1/29.0 °C) and waterlogging events (0 d, 3 d, 6 d) during flowering and boll development. The results showed that the effects of waterlogging stress and elevated temperature in isolation on nitrogen metabolism were quite different. Waterlogging stress not only limited NR (EC 1.6.6.1) and GS (EC 6.3.1.2) activities through the down-regulation of GhNR and GhGS expression for amino acid synthesis, but also promoted protein degradation by enhanced protease activity and peptidase activity, leading to lower organ and total biomass (reduced by 12.01%-27.63%), whereas elevated temperature inhibited protein degradation by limited protease activity and peptidase activity, promoting plant biomass accumulation. Furthermore, 2-3 °C chronic elevated temperature alleviated the negative impacts of a brief (3 d) waterlogging stress on cotton leaves, with the expression of GhNiR up-regulated, the activities of NR, GS and GOGAT (EC 1.4.7.1) increased and the activities of protease and peptidase decreased, leading to higher protein concentration and enhanced leaf biomass for EW3 relative to AW3. The results of the study suggested that exposure to slightly elevated air temperature improves the cotton plants' ability to recover from short-term (3 d) waterlogging stress by sustaining processes associated with nitrogen assimilation.
... Zhao et al. (2001) speculated that this phenomenon was due to restricted sucrose export from source to sink under K deficiency. Nitrate reductase and glutamine synthetase activities have been reported to be decreased by K deficiency (Ruiz and Romero, 2002;Armengaud et al., 2009), leading to reduced N assimilation in Arabidopsis root (Armengaud et al., 2009) and marked decreases in free amino acid content in tea (Camellia sinensis L) leaves (Ruan et al., 1998). In contrast to that, in our study, free amino acid content was significantly increased in the K-deficient leaves compared to the control (Fig. 3C). ...
Reproductive success in higher plants requires a lot of energy and substance provided by carbohydrate and protein metabolism, and potassium (K) plays an important role in carbohydrate and protein metabolism. However, it is unclear whether K deficiency limits reproductive success by disturbing carbohydrate and protein metabolism. The objectives of this study were to explore the effects of K deficiency on carbohydrate and protein metabolism in subtending leaves, phloem and pistils, and their relationship with reproductive success. A cotton cultivar DP0912 was grown in K-deficient (0 mM K+) and K-sufficient (6 mM K+) nutrient solution in growth chambers. Results showed that Pn of the subtending leaves was decreased under K deficiency, but sucrose, starch and free amino acid contents were markedly increased in the K-deficient leaves, because K deficiency limited the translocation of sucrose and amino acid in phloem. As a result, sucrose and free amino acid contents were reduced by 47.3% and 51.8% in the K-deficient pistils than K-sufficient pistils, which led to further decreases in starch and protein accumulation in the K-deficient pistils. Glucose content was also reduced by 53.1% in the K-deficient pistils than K-sufficient pistils, due to the decreased acid and alkaline invertase activities, since sucrose synthase activity was not affected. Lastly, soluble carbohydrate and ATP contents were lower in the K-deficient pistils than K-sufficient pistils, similarly to the changes of pollen tube growth rate and seed set efficiency. It was concluded that the lower carbohydrate and ATP contents in the K-deficient pistils could not meet the energy requirements of pollen tube growth and seed set. Moreover, protein imbalance also limited pollen tube growth. Those changes resulted in lower seed set efficiency to limit reproductive success
... Nitrogen is an influential element on the plant growth parameters (Eifediyi and Remison, 2010) conducted a study in which they used organic farm fertilizers, and reported that as the dosage increased, the height of the plants, the number of the leaves and the yield also increased. Our results are in agreement with the results published by (Ruiz and Romero, 2002) conducted a study in Spain on nitrogen and potassium use in cucumber in green house conditions, and reported that the yield and the weight of the cucumbers were related with the nitrogen and potassium, and that the yield increased with the increase in the N dosages. (Zhou et al., 2011) conducted a study and reported that the yield with organic fertilizers, N, P and K fertilizers was higher than the yield obtained in the control plots (Ruiz and Romero, 1998) conducted a study and reported that there was a clear and directlyproportional relation between the N dosages and the marketable vegetable yield and the sizes of the cucumbers in the greenhouses. ...
... Potassium is a macronutrient that affects plant growth, quality of grains and fruits. Potassium plays an essential role in plant metabolism (Ruiz and Romero, 2002). In Pakistan, most soils contain relatively large amounts of K occurring as a structural element of primary minerals, i.e. ...
Understanding of soil potassium (K) dynamics is essential for
sustainable crop production. Bioavailability of K depends on
forms and distribution within the soil profile. The objectives of
this research were to determine which soil K forms control the
maize (Zea mays) K contents and compare the extracting capability
of sodium tetraphenylborate (NaTPB) with ammonium acetate
(NH4OAc) method. Nine soils representing three different parent
materials, i.e. loess, sandstone and shale were sampled at three
surface genetic horizons. Within each parent material, three soils
at varying level of development were selected. Besides basic soil
parameters, K was fractioned into water soluble K, exchangeable
K, non-exchangeable K, and NaTPB-extracted K. The maize was
sown in pots having 2 kg soil from each genetic horizon. Crop was
harvested at seven weeks and plant was analysed for K contents.
Results show that NaTPB-extracted K gave best correlation as
compared to NH4OAc method. This conveys that a non-exchangeable
K portion that becomes available to plants can be better estimated
by NaTPB method than NH4OAc extraction.
... A 100-μl aliquot was taken for NO − 3 determination and added to 10% (w/v) salicylic acid in H 2 SO 4 at 96%. The absorbance of the solution was measured with a spectrophotometer at A410 nm according to Ruiz and Romero (2002). Leaf K content was determined following H 2 SO 4 -H 2 O 2 digestion using an atomic absorption spectrophotometer (SpectAA-50/55, Varian, Australia) (Hu et al., 2015). ...
To evaluate the role of potassium (K) in maintaining nitrogen metabolism and osmotic adjustment development of cotton functional leaves to sustain growth under soil drought and rewatering conditions, the plants of two cotton cultivars Siza 3 (low-K sensitive) and Simian 3 (low-K tolerant), were grown under three different K rates (K0, K1, and K2; 0, 150, and 300 kg K2O ha⁻¹, respectively) and exposed to drought stress with 40 ± 5% soil relative water content (SRWC). The drought stress was applied at flowering stage by withholding water for eight days followed by rewatering to a well-watered level (75 ± 5% SRWC). The results showed that drought-stressed plants of both cultivars showed a decrease in leaf relative water content (RWC) and osmotic potential in the functional leaves and developed osmotic adjustment with an increase in the contents of free amino acids, soluble sugars, inorganic K, and nitrate as compared to well-watered plants. In drought-stressed plants, nitrogen-metabolizing enzyme activities of nitrogen reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT) were diminished significantly (P ≤ 0.05) along with decreased chlorophyll content and soluble proteins. However, drought-stressed plants under K application not only exhibited higher osmotic adjustment with greater accumulation of osmolytes but also regulated nitrogen metabolism by maintaining higher enzyme activities, soluble proteins, and chlorophyll content in functional leaves as compared to the plants without K application. Siza 3 showed better stability in enzyme activities and resulted in 89% higher seed cotton yield under K2 as compared to K0 in drought-stressed plants, whereas this increase was 53% in the case of Simian 3. The results of the study suggested that K application enhances cotton plants’ potential for sustaining high nitrogen-metabolizing enzyme activities and related components to supplement osmotic adjustment under soil drought conditions.
... The objectives of this study were (1) 79 to explore the effects of K deficiency on C metabolism, N metabolism and C/N balance in cotton 80 leaves in more detail, and (2) to investigate the effects of K deficiency on the export of C and N 81 metabolites in phloem and its relationship with C/N balance in leaves. Ruiz and Romero (2002). Dried leaves (0.2 g) were extracted with 10 mL Millipore-filtered water. ...
Potassium (K) plays important roles in the metabolism of carbon (C) and nitrogen (N), but studies of K deficiency affecting C-N balance are lacking. This study explored the influence of K deficiency on C-N interaction in cotton leaves by conducting a field experiment with cotton cultivar DP0912 under two K rates (K0: 0 kg K2O ha⁻¹ and K67: 67 kg K2O ha⁻¹) and a controlled environment experiment with K-deficient solution (K1: 0 mM K⁺) and K-sufficient solution (K2: 6 mM K⁺). The results showed that leaf K content, leaf number, leaf area, boll number, reproductive dry weight and total dry weight were significant lower under K deficiency (K0 or K1). Lower total chlorophyll content and Chl a/b ratio, and decreased Pn along with lower Gs and higher Ci were measured under K deficiency, suggesting that the decrease in Pn was resulted from non-stomatal limitation. Leaf glucose, fructose, sucrose and starch contents were higher under K deficiency, because lower sucrose export was detected in phloem. Although leaf nitrate and ammonium contents significantly decreased, free amino acid content was increased by 40–63% under K deficiency, since lower amino acid export was also measured in phloem. K deficiency also induced lower soluble protein content in leaves. Leaf ATP level was significantly increased under K deficiency, indicating ATP utilization was lower, so that less energy was supplied to C and N metabolism. The ratio of soluble sugar to free amino acid and the C/N ratio markedly increased under K deficiency, and one reason was that the phloem export reduced more prominent for sucrose (54.6–78.0%) than amino acid (36.7–85.4%) under K deficiency. In addition, lower phosphoenolpyruvate carboxylase activity limited malate and citrate biosynthesis under K deficiency, causing a decrease of C flux into the amino acids, which was not beneficial for maintaining C-N balance. Sucrose phosphate synthase and nitrate reductase activities were lower under K deficiency, which would limit sucrose biosynthesis and nitrate assimilation. This was another factor altering soluble sugar to free amino acid ratio and C/N ratio in the K-deficient leaves.
... Pickling cucumbers are widely consumed as fresh or processed products, thus assessment of nitrates content, as an important indicator of their quality, should be taken into consideration due to their potential impact on people health 544 (Susin et al., 2006). Various studies have reported the nitrates content of cucumbers resulted from field crops (Mahmoud et al., 2009), protected crops (Ruiz and Romero, 2002;Tamme et al., 2010), different growing seasons (Tamme et al., 2010), different time of harvest (Amr and Hadidi, 2001) and domestic or import supply (Tamme et al., 2010). ...
Pickling cucumbers are highly important both for fresh consumption and for canning industry. This study aimed to compare differences in yield and quality of eight pickling cucumber cultivars, The cucumber cultivars were laid out in a high tunnel crop and evaluated for vegetative traits (i.e. vine length, nodes per vine and branches per vine), yield attributes (i.e. fruits per main stem, average weight of fruit and fruits weight per plant) and fruits quality components (nitrate, phosphate and potassium mg kg-1). The results showed significant differences (P<0.05) in vegetative traits and yield attributes among cultivars. The analysis of correlation coefficients revealed that total yield (kg ha-1) was positively correlated with two out of three vegetative traits (with exception nodes per plant) and with all yield attributes. The highest total yield (101.17 t ha-1) was reached by 'SM 5322' cultivar, followed by the 'IGG 2010' and 'SM 5323' cultivars. The nitrates content in fruits, assessed on three categories of length (6-9 cm, 9-12 cm and >12 cm), revealed a declining value with increase in the cucumber length. The study findings suggest that irrespective of the cultivar, the amount of nitrate was higher in shorter cucumbers (6-9 cm length) although all recorded values (between 192.7 and 364.3 mg kg-1 fresh matter) being under maximum accepted limit concentrations. The amount of phosphate was higher in medium to long cucumbers, while the amount of potassium was higher in shorter cucumbers.
... Increase in the rate of potassium application facilitates uptake and transport of nitrate towards the aerial parts of the plant, promotes the metabolism and utilization of nitrate and, ultimately, reduces nitrate accumulation in some vegetable crops (Ahmed et al., 2000;Ruiz and Romero, 2002). However, some studies have indicated that the soil potassium resources have no effect on nitrate accumulation (Drlik and Rogl, 1992). ...
... Potassium (K) is regarded as one of the major nutrient element which affects the yield and quality of grain and fruits. This nutrient plays an essential role in plant growth and metabolism 1,2 . It activates enzymes, serves as an osmoticum to maintain tissue turgor pressure, regulates the opening and closing of stomata, and balances the charge of anions 3,4 . ...
This study was carried out to determine the effects of potassium and different levels of iron foliar applications on growth, yield and nutrient statusof wheat plant grown in sandy soil. Two field experiments were conducted during two successive winter seasons of 2012/2013 and 2013/2014 in Research and Production Station, National Research Centre, Al-Nubaria District, Al Behaira Governorate, Egypt. The experimental design was split-plot in randomized complete block design with three replicates. This experiment includes six treatments in three replicates which were control (without K and Fe), foliar spraying with K (10000 ppm), Fe (500& 1000 ppm), K (10000 ppm) + Fe (500 ppm) and foliar spray with K (10000 ppm) + Fe(1000 ppm). The evidences provided by this experiment indicated that either potassium or iron applications lonely or combined had significant effects on growth, yield and nutrient concentration of wheat leaves, straw and grains and the highest record obtained by low level of Fe alone or combined with K.
... It activates enzymes and is required for carbohydrate metabolism and translocation, nitrogen metabolism and protein synthesis, and regulation of cell sap concentration. This essential nutrient helps in vigorous growth of tomato and stimulates in early flowering and setting of fruits, thereby increasing the number and production of tomato berries per plant (Bergmann, 1992;Ruiz & Romero, 2002). ...
In this paper were studied the effects of the irrigation and the potassium fertilisation on the content of the volatile substances (characteristic volatile compounds: hexanal, 2(E)-hexenal, 2-isobutylthiazole and contributor volatile compounds: alcohols, carbonilic compounds = aldehydes + chetons, sulfurs, terpens, phenolic compounds), soluble sugars (glucose, fructose), pH, organic acids (oxalic, malic, citric), dry matter for alimentary quality and of lycopene for nutraceutical one. The volatile substances were extracted and concentrated from vegetable by microwave-resin-solvent and then analysed quali-quantitatively by GC/MS; while the soluble sugars, organic acids and lycopene by HPLC. As concern the alimentary quality, in Corbarino the content of characteristic volatile compounds increased in the irrigated and fertilisated samples, and in Vesuviano unirrigated and unfertilised. For the contributor volatile compounds, an increase was observed only for alcohols or for all the classis of compounds respectively in Corbarino and Vesuviano in the unirrigated samples with or without fertilization. As concern the other alimentary parameters, no influence of two cultural techniques was ascertained on pH and the content of fructose and oxalic acid for both genotypes. While only in Vesuviano was noted a decrease of dry matter in the irrigated samples. Besides in the unirrigated samples, with or without fertilization, the content of oxalic acid and glucose respectively in Corbarino and Vesuviano. But an increase of the content of citric acid was ascertained in Vesuviano in the unirrigated and fertilized samples. As concern the nutraceutical quality, a light increase of lycopene was observed in both genotypes in the irrigated samples with or without fertilization.
... Accumulation of salt in the soils can alleviate nitrate accumulation in vegetable crops to high fertilization and poor water supply, the water potential of the soil may become so negative that salination takes place and plants take up and accumulate nitrate as an osmoticum to adapt to water conditions. In such a situation, potassium compensates for the increased nitrate in maintaining the electroneutrality of the plant (Ruiz and Romero 2002;Chung et al. 2005;Gairola et al. 2009). ...
2 Turkey is divided in three main phytogeographical regions; one of these is the Mediterranean. The total gene pool of wild species and land races of cultivated plants has a great potential in the plant cover of this region. The studies undertaken in this region revealed that large levels of fertilizers, in particular nitrates, are used in thousands of greenhouses and on the farms, most of these being used unknowingly. A large number of producers apply both inorganic as well as organic fertilizers. The amount varies between 40–75 kg/da fertilizer, which is tenfold of the average recommended for the area. The excessive use of these fertilizers under long periods of drought to leads accumulation of nitrates in plants, which in turn poses a great threat as a potential pollution source for the soils and waters of the region. This paper presents an overview of the results published on the nitrate pollution and accumulation in the plants of this region. ABSTRACT
... The uptake rate of the accompanying cation also affects the proportion of NO 3 − reduced in shoots. With K as the accompanying cation, translocation of both K and NO 3 − to shoots is rapid while correspondingly, Advances in Agronomy, First Edition, 2013, 205-398 NO 3 − reduction is relatively low (Ruiz and Romero, 2002). In contrast, when Ca or Na is the accompanying cation, NO 3 − reduction in roots is increased significantly (Cramer et al., 1995). ...
Nitrogen (N) is the most important, essential nutrient for all living organisms on earth; it is present in a number of complex organic molecules and plays extremely important roles in their activities. Ammonium N (NH4+-N) and nitrate N (NO3--N) are the main forms taken up by plants in addition to some organic N compounds. More than 90% soil N is in organic form. The intermediate products of complicated organic N substances can be absorbed by plants. Organic N nutrition affects plant product quality and plant metabolism. Organic N passes through the cell wall and arrives at the plasma membrane through the apoplast and cytoplast systems and, in addition to endocytosis, may get transported across the plasma membrane by an active (sugar/proton cotransport) or passive process. After uptake by plants, simple organic N compounds such as amino acids can be rapidly assimilated and transformed into other amino acids by transamination and deamination. The uptake of NH4+-N and NO3--N can be described by the Michaelis-Menten equation, and two parameters, the maximum absorption velocity (Vmax) and affinity constant or Michaelis constant (Km), have been used to measure the ability and efficiency of roots absorbing The two ions of crop plants. The uptake amounts of both NH4+-N and NO3--N at the seedling stage are well in agreement with their absorption kinetic parameters, particularly at low concentrations, but are not fully in agreement with the entire growing periods of crops.
Contamination of soils with chromium (Cr) jeopardized agriculture production globally. The current study was planned with the aim to better comprehend how melatonin (Mel) and hydrogen sulfide (H2S) regulate antioxidant defense system, potassium (K) homeostasis, and nitrogen (N) metabolism in tomato seedlings under Cr toxicity. The data reveal that application of 30 μM Mel to the seedlings treated with 25 μM Cr has a positive effect on H2S metabolism that resulted in a considerable increase in H2S. Exogenous Mel improved phytochelatins content and H+-ATPase activity with an associated increase in K content as well. Use of tetraethylammonium chloride (K+-channel blocker) and sodium orthovanadate (H+-ATPase inhibitor) showed that Mel maintained K homeostasis through regulating H+-ATPase activity under Cr toxicity. Supplementation of the stressed seedlings with Mel substantially scavenged excess ROS that maintained ROS homeostasis. Reduced electrolyte leakage and lipid peroxidation were additional signs of Mel's ROS scavenging effects. In addition, Mel also maintained normal functioning of nitrogen (N) metabolism and ascorbate-glutathione (AsA-GSH) system. Improved level of N fulfilled its requirement for various enzymes that have induced resilience during Cr stress. Additionally, the AsA-GSH cycle's proper operation maintained redox equilibrium, which is necessary for the biological system to function normally. Conversely, 1 mM hypotaurine (H2S scavenger) abolished the Mel-effect and again Cr-induced impairment on the above-mentioned parameters was observed even in presence of Mel. Therefore, based on the observed findings, we concluded that Mel needs endogenous H2S to alleviate Cr-induced impairments in tomato seedlings.
Chapter 6 of Marschner's Mineral Nutrition of Plants, Fourth Edition. This book presents sections on the uptake and transport of nutrients in plants, root-shoot interactions, the role of mineral nutrition in yield formation, stress physiology, water relations, functions of mineral nutrients and contribution of plant nutrition to nutritional quality and global nutrition security of human populations.
Other sections focus on the effects of external and internal factors on root growth, rhizosphere chemistry and biology, and nutrient cycling. In addition, this updated edition includes color figures and a new chapter on the impacts of climate change on soil fertility and crop nutrition. An understanding of the mineral nutrition of plants is of fundamental importance in both basic and applied plant sciences. The fourth edition of this book retains the aim of the first in presenting the principles of mineral nutrition in the light of current advances.
Foliar nitrogen (N) application is an effective strategy to improve protein content and quality in wheat kernels, but the specific effects of N forms remain unclear. In a two-year field study, foliar application of various N forms (NO3-, urea, NH4+) at anthesis was performed to measure their effects on wheat grain protein accumulation, quality formation, and the underlying mechanisms. Foliar application of three N forms showed varying effects in improving grain gluten proteins and quality traits. Under NH4+ application, there was more post-anthesis N uptake for grain filling, with relatively strong increase in enzyme activities and gene expression associated with N metabolism in flag leaves at 8−20 days after anthesis (DAA), whereas its promotion of grain N metabolism became weaker after 20 DAA than those under NO3- and urea treatments. More N was remobilized from source organs to grain under treatment with foliar NO3- and urea. Genes controlling the synthesis of gluten protein and disulfide bonds were upregulated by NO3- and urea at 20−28 DAA, contributing to increased grain protein content and quality. Overall, foliar applications of NO3- and urea were more effective than those of NH4+ in increasing grain N filling. These findings show that manipulating the source–sink relationship by reinforcing grain N metabolism and N remobilization is critical for optimizing grain protein accumulation and quality formation.
Background
Many studies have indicated that straw-returning could meet part or even all of the potassium (K) demand for crop growth in the field, but few have compared the effects of crop straw as K source and inorganic K fertilizer on carbon–nitrogen (C–N) balance of cotton and the reproductive growth. To address this, field experiments were conducted using the cotton cultivar, Siza 3, under there treatments (CK as control group one, no crop straw and inorganic K fertilizer were applied; K150 as control group two, 150 kg·ha ⁻¹ of K 2 O was applied; and W9000, 9 000 kg·ha ⁻¹ wheat straw, which could provide K 2 O about 150 kg·ha ⁻¹ , was incorporated into soil).
Results
Although the final reproductive organ biomass did not differ between W9000 and K150, W9000 had a higher ratio of reproductive organ biomass to total biomass (RRT), suggesting that straw-returning was more conducive to the allocation of biomass to reproductive organs. The theoretical maximum biomass of reproductive organ was higher, but the average and maximum accumulation rates of reproductive organ biomass were 2.8%∼8.3% and 2.5%∼8.2% lower under W9000 than K150. Also, the duration of rapid-accumulation period for reproductive organ biomass (T) was 2.0∼2.8 d longer under W9000 than K150, which was a reason for the higher RRT under W9000. Straw-returning altered the dynamics of leaf K with the growth period, so that W9000 had a more drastic effect on leaf C metabolism than K150. Consequently, lower soluble sugar/free amino acid and C/N ratios were measured under W9000 than K150 at boll-setting (BSS) and boll-opening (BOS) stages. Higher leaf net photosynthetic rate, sucrose phosphate synthase and sucrose synthase activities, and lower acid invertase activity were observed under W9000 than K150 at BSS and BOS and these were more conducive to sucrose accumulation. However, less sucrose was measured under W9000 than K150 at these stages. This should be because straw-returning promoted the assimilate transport capacity when compared with inorganic K fertilizer application, which also explained the higher RRT under W9000 than K150. The lower acid invertase activity under W9000 inhibited the conversion of sucrose to other sugars, hence lower contents of soluble sugar and starch were measured under W9000 than K150.
Conclusion
Under low K condition, crop straw as K source can increase the assimilate transport from source to sink, leading to lower C/N ratio in leaf and higher allocation of biomass to reproductive organs than inorganic K fertilizer.
This study was conducted to monitor the changes in different forms of soil K. The study concerned analysis of soil taken from an experiment having different NPK, FYM executed in a randomized complete block design. The treatments were eleven as follows:-N 36 ,
The middle and lower reaches of Yangtze River present high rainfall and always have a high water table. Recently drip fertigation has been introduced and widely used for vegetable production in this area. To investigate the effect of shallow groundwater and the newly-developed fertigation on the cucumber water and nitrogen (N) requirement, experiments were carried out in plastic tunnels in Yangzhou, Jiangsu, China, during the 2016 and 2017 growing seasons using a randomized block design with three replicates. Four N rates, 4 irrigation amounts and 2 irrigation intervals (2 d and 4 d) were applied in this experiment. The results showed that irrigation amount of 75% of estimated plant evapotranspiration (ET c ) was optimal to obtain the highest yield, indicating shallow groundwater had a considerable contribution to the cucumber plant evapotranspiration in this condition. Fertigation technology improved the irrigation water use efficiency (IWUE) and N use efficiency (NUE) and 75% of the recommended N rate (calculated according to a traditional local nutrient balance method) optimized cucumber yield. Frequent irrigation with low water volume had a beneficial impact on the improvement of cucumber yield, IWUE, NUE and reduced the N leaching. According to this work, the recommended fertigation strategy is 0.75 of recommended N, 0.75 estimated ET c and 2 d irrigation interval in this experiment, in which cucumber yield of 105.4 Mg ha ⁻¹ , IWUE of 41.1 kg m ⁻³ and NUE of 356.4 kg kg ⁻¹ were achieved.
Using organic and inorganic fertilizers concurrently may not only quench the crop nutritive demands but also been proved an eco-friendly nutrient source. In order to evaluate the effect of potassium (K) application from only inorganic, integrated organic and inorganic sources of fertilizers on maize, a field study was conducted during 2008 and 2009 following randomized complete block design (RCBD) with three replications at Agronomic Research Area, University of Agriculture, Faisalabad, Pakistan. In this study composted wheat and rice straws were integrated with the sulphate of potash (SOP) as K source. Regarding application of K from the integrated sources, treatment containing 25% composted rice straw + 75% SOP provided highest leaf area index (LAI; 5.13 and 5.11), eaf area duration (LAD; 217.33 and 219.65 days), crop growth rate (CGR; 28.94 and 29.08 g m-2 d-1), total dry matter (TDM; 1,925.03 and1,931.32 g m-2), and gave prominent plant height (215.50 and 218.63 cm), 1,000-grain weight (262.87 and 266.63 g), grain yield (7.02 and 7.38 t ha-1), biological yield (16.63 and 17.37 t ha-1) and harvest index (42.22 and 42.49%) during both the years (2008-09), respectively. Moreover, given years, the integrated use of 25% composted rice straw + 75% SOP earned maximum benefit cost ratio of 2.12 and Rs. 2.22, respectively. Conclusively, integrated use of organic amendments of K with inorganic source might be a better technique over separate application of inorganic source. © 2015, Consiglio per la Ricercame la sperimentazione in Agrcoltura. All Rights Reserved.
The nitrogen (N) metabolism of the leaf subtending the cotton boll (LSCB) was studied with two cotton (Gossypium hirsutum L.) cultivars (Simian 3, low-K tolerant; Siza 3, low-K sensitive) under three levels of potassium (K) fertilization (K0: 0 g K2O plant−1, K1: 4.5 K2O plant−1 and K2: 9.0 g K2O plant−1). The results showed that total dry matter increased by 13.1-27.4% and 11.2-18.5% under K supply for Simian 3 and Siza 3. Boll biomass and boll weight also increased significantly in K1 and K2 treatments. Leaf K content, leaf N content and nitrate (NO3ˉ) content increased with increasing K rates, and leaf N content or NO3ˉ content had a significant positive correlation with leaf K content. Free amino acid content increased in the K0 treatment for both cultivars, due to increased protein degradation caused by higher protease and peptidase activities, resulting in lower protein content in the K0 treatment. The critical leaf K content for free amino acid and soluble protein content were 14 mg g-1 and 15 mg g-1 in Simian 3, and 17 mg g-1 and 18 mg g-1 in Siza 3, respectively. Nitrate reductase (NR), glutamic-oxaloace transaminase (GOT) and glutamic-pyruvic transaminase (GPT) activities increased in the K1 and K2 treatments for both cultivars, while glutamine synthetase (GS) and glutamate synthase (GOGAT) activities increased under K supply treatments only for Siza 3, and were not affected in Simian 3, indicating that this was the primary difference in nitrogen-metabolizing enzymes activities for the two cultivars with different sensitivity to low-K.
Respected and known worldwide in the field for his research in plant nutrition, Dr. Horst Marschner authored two editions of Mineral Nutrition of Higher Plants. His research greatly advanced the understanding of rhizosphere processes and trace element uptake by plants and he published extensively in a variety of plant nutrition areas. While doing agricultural research in West Africa in 1996, Dr. Marschner contracted malaria and passed away, and until now this legacy title went unrevised. Despite the passage of time, it remains the definitive reference on plant mineral nutrition. Great progress has been made in the understanding of various aspects of plant nutrition and in recent years the view on the mode of action of mineral nutrients in plant metabolism and yield formation has shifted. Nutrients are not only viewed as constituents of plant compounds (constructing material), enzymes and electron transport chains but also as signals regulating plant metabolism via complex signal transduction networks. In these networks, phytohormones also play an important role. Principles of the mode of action of phytohormones and examples of the interaction of hormones and mineral nutrients on source and sink strength and yield formation are discussed in this edition. Phytohormones have a role as chemical messengers (internal signals) to coordinate development and responses to environmental stimuli at the whole plant level. These and many other molecular developments are covered in the long-awaited new edition. Esteemed plant nutrition expert and Horst Marschner's daughter, Dr. Petra Marschner, together with a team of key co-authors who worked with Horst Marschner on his research, now present a thoroughly updated and revised third edition of Marschner's Mineral Nutrition of Higher Plants, maintaining its value for plant nutritionists worldwide. A long-awaited revision of the standard reference on plant mineral nutrition Features full coverage and new discussions of the latest molecular advances Contains additional focus on agro-ecosystems as well as nutrition and quality.
A field trial was conducted at the experimental farm of the Department of Crop Protection and Environmental Biology, University of Ibadan, Nigeria, to determine the growth and yield response of cucumber (cv. Poinsett) to timing of fertilizer application. Fertilizer (20:10:10), at the rate of 150 kg N ha -1, was applied at: planting, 3 weeks after planting (WAP) and 6 WAP. Similarly, split applications were given at planting + 3 WAP, at planting + 6 WAP and at 3 WAP + 6 WAP. The experimental design was a randomized complete block with seven treatments (six fertilizer application treatments plus a non fertilizer control) and four replications. Means were separated using Duncan's Multiple Range Test at the 5% level of significance. In general, plants that were fertilized performed better than control plants in terms of vegetative growth and yield. A split application at 3 WAP + 6 WAP performed the best in terms of vegetative growth and fruit yield. Fertilizer applied once-over at 6 WAP was the least beneficial; application of fertilizer once-over at planting, or a split application at planting + 3 WAP, resulted in a high level of vegetative growth but lower fruit yield compared with the split application at 3 WAP + 6 WAP.
Plant nitrogen metabolism is regulated by nitrogen supply and by plant demand for growth. In recent years it has become evident that many of the processes and metabolic pathways of plant nitrogen metabolism are regulated by the concentration of all or several amino acids and amides. The role of amino acids and amides in the regulation of nitrate and ammonium uptake, nitrate reduction, ammonium incorporation, protein metabolism and N remobilization is discussed. It is proposed that as the free amino-acid concentrations are dependent on the plant N status, changes in their cytoplasmic concentration may be involved in the regulation of plant growth and N uptake.
The capacity of poplar (P. tremula x P. alba, clone INRA 717 1/B4) to respond to changes in the nutrient supply with modifications in the xylem exudate collected after decapitation was investigated with special respect to N-compounds. The composition (inorganic ions and amino-N) was analysed with respect to (a) the time after decapitation at different times of day, (b) a change in the nitrogen concentration from NO-/3 to N-free medium, (c) a change in the nitrogen source from NO-/3 to NH4+, (d) an increase in NO-/3 supply from 1 mM to 8 mM, and (e) the withdrawal of K+ supply. (a) The ion concentration in the xylem exudate was not affected up to 15 min after decapitation of the plants. Later a continuous increase in the concentration was observed. This increase was large if decapitation was performed in the middle of the light period and small at night-time. In both types of experiments (b, c) the NO3 concentration dropped immediately after the transfer, indicating the close connection between NO-/3 uptake and xylem loading. (b) After transfer to N-free medium poplar did not balance the charge in the xylem by increasing the concentration of other inorganic anions or decreased xylem loading of cations within 3 d of treatment. The N-status of the xylem exudate was reduced within 15 min. (c) After transfer of the NO3/--grown plants to NH2/+, as the sole N-source, the charge compensation in the xylem exudate was maintained by reducing the loading of cations, and 3 d later by an enhanced xylem loading of mainly SO2-/4. an immediate increase in glutamine concentration (2-fold in 15 min). (d) Increasing the NO-/3 supply to 8 mM had no effect on the ionic composition or the N-status of the xylem exudate. (e) The withdrawal of K+ from the medium for 11 d resulted in a limitation of the S- and N-supply of the plant, causing a decrease in the N-status of the xylem sap. The data are discussed with respect to charge compensation after changes in the nutrient supply and to the maintenance of the nitrogen status in the xylem sap.
Plant nitrogen metabolism is regulated by nitrogen supply and by plant demand for growth. In recent years it has become evident that many of the processes and metabolic pathways of plant nitrogen metabolism are regulated by the concentration of all or several amino acids and amides. The role of amino acids and amides in the regulation of nitrate and ammonium uptake, nitrate reduction, ammonium incorporation, protein metabolism and N remobilization is discussed. It is proposed that as the free amino-acid concentrations are dependent on the plant N status, changes in their cytoplasmic concentration may be involved in the regulation of plant growth and N utpake.
An analysis is described for the rapid determination of nitrate‐N in plant extracts. The complex formed by nitration of salicylic acid under highly acidic conditions absorbs maximally at 410 nm in basic (pH>12) solutions. Absorbance of the chromophore is directly proportional to the amount of nitrate‐N present. Ammonium, nitrite, and chloride ions do not interfere.
The measurement of NH4‐N in soil, and plant digests is one of the greatest needs in laboratories conducting agricultural and environmental research. Many laboratories do not have access to automated equipment for colorimetric analysis of soil and plant digests. The objective of this research was to modify an automated colorimetric analysis procedure for determining NH4+‐N in soil and plant digests for manual use, and compare the proposed technique with the standard distillation‐titration technique. The modified procedure is based on the color reaction between NH4 ‐ and a weakly alkaline mixture of Na salicylate and a chlorine source in the presence of Na nitroprusside. Wavelength scans indicated a very well defined peak for determinations at 650 nm. Time scans showed that color development in the manual procedure was rapid, 12 to 40 minutes depending on temperature, and that the color development remained stable for at least 120 minutes. Regression analysis of the results from 18 soil and 20 plant tissue sample determinations by distillation‐titration and the proposed method indicated NH4 ‐N recoveries of 99% or higher. The results obtained using the colorimetric procedure were very similar to the values obtained by distil ling and titrating the digests for both soil and plant samples as indicated by the large coefficients of determination (R= 0.99).
Diurnal variations of in vitro activity of 5 enzymes of nitrogen metabolism were studied. Barley (Hordeum vulgare L. cv. Herta) seedlings were grown in 8 h short days, in daylight or under fluorescent lamps. During, the photoperiod nitrite reductase (EC 1.7.7.1) increased by an average of 18% in daylight and 10% under fluorescent lamps. Glutamine synthetase (EC 6.3.1.2) activity increased by 14 and 10%, respectively. The increase in enzyme activity reflected the overall increase in soluble proteins which was 8% in daylight and 3% under fluorescent lamps. Alanine aminotransferase (EC 2.6.1.2) increased by 82% in daylight and 37% under fluorescent lamps. Desalting of the extracts did not alter the enzyme activity and thus supported the assumption that changes in extractable enzyme activity are due to changes in the amount of (active) enzyme protein. Glutamate synthase (EC 1.4.7.1) activity did not show regular diurnal variations, and aspartate aminotransferase (EC 2.6.1.1) activity was almost constant.
The effect that application of nitrogen-phosphorus (NP) rates exerts on some parameters of phosphorus metabolism in eggplant (Solanum melongena cv. Bonica) was studied. All plants were grown under controlled conditions in an experimental greenhouse. The treatments consisted of the combination of three rates of N in the form of KNO 3 (N 1) 15 g m -2 ; N 2) 22.5 g m -2 ; and N 3) 30 g m -2) together with two rates of P in the form of H 3 PO 4 (P 1) 24 g m -2 and P 2) 36 g m -2), for a total of six treatments. The results obtained show a positive effect of NP fertilization on the nutritional status of P in the plants, clearly reflected in the response of bioindicators of the P (acid phosphatase activity and carbohydrates). The plants treated with N 3 P 2 registered greater integration or assimilation of inorganic P to organic P, a fact that may be related to the maximum total and commercial yield in these plants and minimum noncommercial yield.
Twelve different tomato (Lycopersicum esculentum Mill.) genotypes were grown in a controlled greenhouse to determine the influence of genotype variation on the efficiency of nitrogen utilization and fruit yield. The results showed that the variation of genotype in tomatoes influences the utilization and assimilation of foliar NO 3 -. The genotypes that proved highly efficient in this utilization were G7, G9, G11, and G12. These genotypes had the highest foliar NO 3 -concentrations, greatest nitrate reductase activities, and highest protein and organic nitrogen contents. Genotype also influenced marketable and nonmarketable yields. Genotypes G2, G3, G6, and G8, which ranked intermediate in the efficient utilization of N, had the highest marketable and lowest nonmarketable yields.
The effect of application of different phosphorus rates on some parameters of nitrogen metabolism and yield in cucumber plants (Cucumis sativus L cv Brunex) was studied. All plants were grown under controlled conditions in an experimental greenhouse. The treatments consisted of applications of P at three rates in the form of H3PO4 (P1, 4 g m−2; P2, 8 g m−2; P3, 16 g m−2). The results showed a positive effect of higher P fertilisation (8 and 16 g m−2) on uptake, translocation and assimilation of in the leaves compared with the lowest P dose (4 g m−2), indicating that P is involved in the processes related to N metabolism in the leaves. In addition, the higher P rates strengthened the translocation of organic nitrogenous compounds (amino acids) towards the fruit, thereby perhaps also enhancing the maximal commercial yield. In conclusion, for improved cucumber cultivation under greenhouse conditions, 8 g m−2 gave maximal yield, while 16 g m−2 increased the metabolism and efficient utilisation of N.© 2000 Society of Chemical Industry
Cucumber plants (Cucumis sativus L. cv. Brunex) were grown under controlled conditions in an experimental greenhouse and treated with four rates of N in the form of KNO3 (N1, 5 g/m2; N2, 10 g/m2; N3, 20 g/m2; and N4, 40 g/m2). The intermediate N rates (N2 and N3) gave higher utilization of NO3− in the leaves (highest NR activities) than treatment N1 (inadequate) and N4 (excessive). This latter rate (N4) appears to result in excessive foliar assimilation of NO3−, thereby increasing amino acids and proteins and inhibiting or reducing NR activity. N2 and, especially, N3 treatments strengthened the translocation of organic nitrogenous compounds (amino acids) towards the fruit, which enhanced the commercial yield.
Mineral nutrients taken up by the roots are, as a rule, transported in the xylem to the shoot, and photoassimilates transported in the phloem to the roots. According to the Thornley model of photosynthate partitioning, nutrient deficiencies should favour photosynthate partitioning to the roots. Examples are cited to show that this preferential partitioning is dependent on phloem mobility and hence on nutrient cycling from shoot to roots. Thus, root growth is enhanced under nitrogen and phosphorus deficiencies, but not under deficiencies of nutrients of low mobility in the phloem, such as calcium and boron. Enhanced root growth under nutrient deficiency relies on the import of both photosynthates and mineral nutrients.
Cycling of mineral nutrients serves a number of other functions. These include the root supply of nutrients assimilated in the shoot (nitrate and sulphate reduction), maintenance of cation-anion balance in the shoot, providing an additional driving force for solute volume flow in the phloem and xylem, and acting as a shoot signal to convey nutrient demand to the root.
Cycling of certain mineral nutrients through source leaves has a considerable impact on photosynthate export as demonstrated in impaired export under magnesium, potassium, or zinc deficiencies. Mineral nutrient deficiency can, therefore, affect photosynthate partitioning either directly via phloem loading and transport or indirectly by depressing sink demand.
Differential flows of photoassimilate result in patterns of dry matter distribution among plant organs. The extent to which
these patterns are dependent on the flux of different mineral nutrients entering the root and the extent to which the distribution
of dry matter in the whole plant is affected by differentials in nutrient (primarily nitrate) flux among parts of the root
system is considered. It is concluded that patterns of dry matter distribution and nutritional status may depend on how nutrient
supply has been manipulated about the root. Where the flux density of nutrient has been decreased and has become limiting
to plant growth, two categories of response have been observed. In the case of N, P or S, limiting flux density results in
a proportionately greater amount of plant dry matter in roots than is found at higher flux densities. This contrasts with
the case of limiting K, Mg or Mn supply, where proportionately less plant dry matter is found in roots at lower nutrient flux
densities than at higher flux densities. In the case of N, particular attention is paid as to how sink strength may be related
to differences between root and leaf cells in their capacity for loosening and synthesis processes in the primary cell wall.
Certain bioregulators were studied in relation to nitrogen metabolism of pepper plants (Capsicum annuum L. cv. Lamuyo). Plants were grown under controlled conditions and submitted to regular fertilization with macro- and micronutrients. Treatments were as follows: nontreated control (T0); fosfonutren [essential amino acids and micronutrients (46.9 mg L(-)(1))] (T1); biozyme [GA(3) (32.2 mg L(-)(1)) plus IAA (32.2 mg L(-)(1)) plus zeatin (83.2 mg L(-)(1)) plus chelated micronutrients] (T2); and GA(3) [16 mg L(-)(1)] (T3). The concentrations of NO(3)(-), organic N, amino acids, and proteins, the activities of nitrate reductase (NR) and nitrite reductase (NiR), and finally the foliar dry weight and yield were analyzed. The results indicated that the application of certain bioregulators, such as fosfonutren (T1), which contain amino acids can cause a negative effect on the efficiency and utilization of NO(3)(-), resulting in a drastic loss in growth and yield, even under the control treatment, in which no bioregulator was applied. On the contrary, the application of certain bioregulators based principally on the combination of different hormones, as in the case of biozyme (T2), increased NO(3)(-) assimilation under our experimental conditions, due possibly to a greater availability of these bioregulators in the leaves and increased NR and NiR activities. This appears to explain why the T2 treatment gave the greatest foliar dry weight and fruit yield per plant in the experiment.
An important factor in photosynthetic ecophysiology is the light regime that a photobiont is acclimated to exploit. In a wide range of cyanobacteria and cyano-lichens, the easily measured fluorescence parameters, coefficient of nonphotochemical quenching of photosystem II variable fluorescence (qN) and nonphotochemical quenching, decline to a minimum near the acclimated growth light intensity. This characteristic pattern predicts the integrated light regime to which populations are acclimated, information that is particularly useful for cyanobacteria or cyano-lichens from habitats with highly variable light intensities. qN reflects processes that compete with photosystem II photochemistry for absorbed excitation energy. In cyanobacteria, we find no evidence for energy-dependent quenching mechanisms, which are the predominant components of qN in higher plants. Instead, in cyanobacteria, qN correlates closely with the excitation flow from the phycobilisome to photosystem I, indicating that qN reflects the state transition mechanism for equilibration of excitation from the phycobilisome to the two photosystems.
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
Current aspects of the enzymes involved in the assimilation of nitrate and ammonium ions are described. The three initial reactions, the uptake and the two reductases (nitrate and nitrite reductase) are turned on in root and leaf tissues by nitrate additions to the medium. In root tissues an isoform of ferredoxin glutamate synthase and of glutamine synthetase are also induced by nitrate. cDNA clones of the enzymes nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase have been reported and regions of the promoter of the nitrite reductase gene which respond to nitrate and light have been defined. Asparagine and glutamine repress the induction of the two reductases and the uptake system but are without effect on protein levels of the other enzymes involved in the assimilation process.
Capsicum plants were grown under controlled conditions and submitted to individual fertilization with varying rates of NK. N was applied as NH4NO3 (N-1: 6 g m(-2), N-2: 12 g m(-2), N-3: 18 g m(-2) and N-4: 24 g m(-2)) and K as K2SO4 (K-1: 4 g m(-2), K-2: 8 g m(-2) and K-3: 12 g m(-2)), resulting in 12 treatments of the corresponding crosses between the different rates of N and K. Applying high rates of N and K led to an increase in the absorption and translocation of NO to the shoot, however, the trend of the NR in the two assays studied (NRc and NRi) and that of NH indicate that this latter ion was the main N form assimilated by the plant. The products resulting from this process, mainly proteins, increased with higher N and K rates, which also gave rise to the maximum leaf concentrations of organic and total P forms, while inorganic P was unaffected. The acid phosphatase activity proved to be a good indicator of the nutritional status of P. Finally, yield in Kg plant(-1) was maximum at N3K1, whereas the greatest number of fruits were maximum at the N4K3 rate.
Rates of photosynthesis of leaf slices from various hygro-, meso- and xerophytes were measured in the absence of stomatal control in various stages of osmotic dehydration. The external osmotic potential π° for a 50% inhibition of photosynthesis varied between 20 bar in some hygrophytes up to 50 bar in xerophytes. The response of photosynthetic enzymes to increased salt concentrations in the reaction medium was similar in leaf extracts from hygro-, meso- and xerophytes. The total protoplast volume in vacuum-infiltrated leaf discs from various plants was measured as the difference between (3)H2O-labeled space and [(14)C]sorbitol-labeled space. In all plants, the protoplast volume could be reduced to about 55% of the maximum volume of tissue in equilibrium with water, without decreasing photosynthesis. Reduction of the maximal protoplast volume below 55% decreased photosynthesis in all tissues to the same decreased photosynthesis in all tissues to the same degree. At 20% maximal volume, photosynthesis of all plants was completely inhibited. The differential decrease of protoplast volumes of various leaf tissues in response to changes in π° was mainly due to the different osmotic potential of the cell sap (πcs). The relative contribution of sugars to the overall osmolarity of the cell sap was up to nineteen times higher in xerophytes than in hygrophytes. Short-term recovery of photosynthesis after hypertonic stress was good in xerophytes, incomplete in mesophytes and absent in hygrophytes. There was also a large discrepancy between the partial recovery of protoplast volumes and the complete absence of a recovery of photosynthesis in hygrophytes.
The effect of different parameters on the in vivo nitrate reductase activity in leaves of maize, soybean, and spinach has been examined. Leaf sections infiltrated under vacuum with an assay medium containing CO2 tension and NO-3 and incubated under air, excreted CO2 tension and NO-2 in the dark but not in the light. Nevertheless, addition of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea, a potent inhibitor of the photosynthetic electron transport, promoted an immediate excretion of CO2 tension and NO-2 in the light. Under those conditions, subsequent addition of ascorbate-reduced dichlorophenolindophenol or N,N,N′,N′-tetramethylphenylenediamine, which can supply electrons to photosystem I, abolished the excretion of CO2 tension and NO-2 by the leaf sections. These results support the view that, in green tissues, the reducing equivalents photogenerated in the chloroplasts are more directly used for NO-2 reduction than for NO-2 reduction.
Incubation of leaf discs under O2-atmosphere severely impaired NO-2 accumulation. Under strict anaerobic conditions, the rate of NO-2 production was only slightly enhanced as compared with that observed in the assay under air. Exogenous NO-3 stimulated the activity, more markedly in soybean than in the other two species. Concentrations of exogenous NO-3 between 50 and 100 mM were required for maximal activities in all the three species. The external pH optimum for in vivo NO-3 reduction was 7.5 for maize and spinach and 7.0 for soybean.
Inclusion of 1% (v/v) n-propanol in the infiltration-incubation medium enhanced the activity about 15%. However, 7% (v/v) n-propanol caused a drastic decrease in the rate of NO-2 accumulation which could be greatly overcome by inclusion in the medium of NADH or reduced flavin mononucleotide.
The effect of K+ as a countercation to NO3− on the reduction of NO3− in the root has been investigated using castor bean (Ricinus communis L.) and barley (Hordeum vulgare L.) grown with reciprocal splitroots. One part of the root system was supplied with a nutrient solution lacking potassium but containing NaNO3 instead of KNO3 (−K+N roots), whereas the other side obtained potassium but no nitrate (+K−N roots). The contribution of the roots to nitrate reduction was assessed firstly by analyzing the proportion of reduced to total nitrogen in the xylem sap and secondly by measuring nitrate reductase activity (NRA) in vivo and in vitro in the roots. −K+N roots of Ricinus contributed more to nitrate reduction in the whole plant than control roots, as shown by a higher ratio of reduced to total nitrogen in xylem sap and by a 2.3- to 2.8-fold higher in vivo NRA. This minus K stimulation of NRA was found also in roots of Hordeum in the NRA measured in vivo (1.9-fold) as well as in vitro (1.6-fold). The minus K stimulation in −K+N roots was reversible within 4 or 6 h and it decreased with a half-time of 43 or 75 min after supply of external K+ or Rb+, respectively. The development of the minus K stimulation, however, was slow. It occurred with a time lag of 4 days and was completed after 10 days exposure to minus K conditions, suggesting that regrowth of new root tissue was involved. NRA in +K−N roots was, as expected, low. These findings suggest that availability of easily permeating countercations to nitrate, such as potassium, plays a role in the regulation of the partitioning of nitrate reduction between shoot and root in the whole plant.
Today's flue-cured tobacco (Nicotiana tabacum L.) cultivars differ significantly in yield and quality from cultivars grown early in the 20th century. One major change in crop management has been an increase in fertilizer use, especially N. In view of the changing fertilization pratices and the current importance of N in crop production, this study was initiated to evaluate genetic variability in N-use efficiency in flue-cured tobacco
The absorption, translocation, and metabolism of N is influenced by the source of N and by the availability and mobility of counter ions for transport. The purpose of this study was to determine the influence of K or Ca on nitrate uptake, translocation, and reduction in barley seedlings (Hordeum vulgare. cv. Compana). Six-day-old barley seedlings were grown for 2 to 36 hours in solutions of 1.0 meq/liter KNO3 or Ca(NO3)2, each containing 0.4 meq/liter of CaSO4. Experiments were conducted in a growth chamber at 27 C with a photosynthetic irradiance of 5.3 mW cm⁻². Seedlings treated with Ca(NO3)2 (low K) had lower levels of nitrate uptake, nitrate reductase activity, and lower organic acid concentrations than seedlings treated with 1 mM KNO3. The solution pH and the expressed sap pH of roots and shoots of the low K seedlings increased during the experiment. The shoots of the low-K seedlings had much lower nitrate concentrations and lower levds of nitrate reductase activity than the roots, suggesting that K plays a major role in nitrate translocation. These results support the hypothesis that potassium malate is cycled from the tops to the roots where decarboxylation occurs, providing a source of HCO3⁻ for exchange with NO3⁻ during absorption.
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Tobacco plants (Nicotiana tabacum cv. Sevilla) were grown under controlled conditions and submitted to regular fertilization with macro- and micronutrients. The aim of the experiment was to determine the response of NO3- assimilation to four different boron (B) doses (B1: 0.5 mu M H3BO3; B2: 5 mu M; B3: 10 mu M H3BO3; and B4: 20 mu M H3BO3). The content of foliar B and NO3-, the activity of the enzymes related to the process of NO3- reduction (NR, NiR, GS, GOGAT, and PEPC), and the end products of this process (amino acids and proteins) were analyzed. Our results indicate a positive effect of the B on its concentration in leaves and on NO3- assimilation, possibly by an activation of the enzymatic proteins involved in this process. Boron addition significantly reduced the foliar NO3- concentration. Finally, B affected plant growth, since an increase in leaf dry weight and in the content of proteins and amino acids was shown.
A comprehensive system for the determination of N,‐ P, K, Ca, Mg, Na, B, Cu, Fe, Zn, S, and F in plant tissue is presented. A wet ash procedure using sulfuric acid and hydrogen peroxide permits determination of N, P, K, Ca, Mg, Na, B, Cu, Fe, Zn in one digest. S and F are determined in solutions of separate dry ashings.The use of leaf analyses and its limitations are discussed.
The capacity of poplar (P. tremula x P, alba, clone INRA 717 1/B4) to respond to changes in the nutrient supply with modifications in the xylem exudate collected after decapitation was investigated with special respect to N-compounds. The composition (inorganic ions and amino-N) was analysed with respect to (a) the time after decapitation at different times of day, (b) a change in the nitrogen concentration from NO3- to N-free medium, (c) a change in the nitrogen source from NO3- to NH4+, (d) an increase in NO3- supply from 1 mM to 8 mM, and (e) the withdrawal of K+ supply. (a) The ion concentration in the xylem exudate was not affected up to 15 min after decapitation of the plants, Later a continuous increase in the concentration was observed. This increase was large if decapitation was performed in the middle of the light period and small at night-time. In both types of experiments (b, c) the NO3- concentration dropped immediately after the transfer, indicating the dose connection between NO3- uptake and xylem loading, (b) After transfer to N-free medium poplar did not balance the charge in the xylem by increasing the concentration of other inorganic anions or decreased xylem loading of cations within 3 d of treatment, The N-status of the xylem exudate was reduced within 15 min. (c) After transfer of the NO3--grown plants to NH4+, as the sole N-source, the charge compensation in the xylem exudate was maintained by reducing the loading of cations, and 3 d later by an enhanced xylem loading of mainly SO42-. The N-status in the xylem exudate was maintained by an immediate increase in glutamine concentration (2-fold in 15 min), (d) Increasing the NO3- supply to 8 mM had no effect on the ionic composition or the M-status of the xylem exudate, (e) The withdrawal of K+ from the medium for 11 d resulted in a limitation of the S-and N-supply of the plant, causing a decrease in the N-status of the xylem sap. The data are discussed with respect to charge compensation after changes in the nutrient supply and to the maintenance of the nitrogen status in the xylem sap.
Whenstomata ofVicia fabaopened (from a stomatal aper- tureofabout2 micrometers tooneof12micrometers) the solute content oftheguardcells increased by4.8X 10-' osmoles perstoma.During thesametimeanaverage of4.0X 10-12 gramequivalents ofK+weretransported intoeachpairof guardcells. ThisamountofK+,ifassociated withdibasic anions, issufficient toproduce thechanges inguard cell volumeandosmotic pressure associated withstomatal opening. Analysis ofCl,P,andS showedthattheseelements werenot transported insignificant amountsduring stomatal opening. Thisfinding suggests thattheanionsbalancing K+were pre- dominantly organic. K+wasspecifically required because no otherelements, likely tobepresent ascations, werefoundto accumulate inappreciable quantities inguardcells ofopen stomata.
The aim of this study was to determine the response of NO3− assimilation in roots and leaves to different CaCl2 application (T1, 1.25 mM CaCl2·2H2O; T2, 2.5 mM CaCl2·2H2O and T3, 5 mM CaCl2·2H2O). Tobacco plants (Nicotiana tabacum cv Sevilla) were grown under controlled conditions and submitted to regular fertilization with macro- and micronutrients. The content of Ca2+, Cl− and NO3−, the activity of the enzymes related to the process of NO3− reduction (NR: nitrate reductase, EC 1.6.6.1; NiR: nitrite reductase, EC 1.7.7.1; GS: glutamine synthetase, EC 6.3.1.2; GOGAT: glutamate synthase, EC 1.4.1.14; PEPC: phosphoenolpyruvate carboxylase, EC 4.1.1.31), and the end products of this process (amino acids and proteins) were analysed in roots and leaves. Our results indicate that the utilization of NO3− in the plant was influenced by the different treatments. NO3− was translocated towards the aerial part and subsequently assimilated in the leaves in treatments T1 and T2, the latter significantly intensifying these processes and giving rise to greater production of dry matter both in the leaves and in the roots. With the T3 treatment, NO3− assimilation occurred principally in the roots, due possibly to decreased NO3− translocation towards the aerial part, thereby increasing its availability in the roots. In addition, the possible negative effect of the maximum foliar concentrations of Ca2+ and Cl− on the foliar activity of NR in this treatment could also cause NO3− assimilation in the roots with the T3 treatment. Finally, it is noteworthy that the application of T3 significantly reduced root growth.
The control of nitrate reductase (NR) activity by reversible protein phosphorylation is a two-stage process: the enzyme is reversibly phosphorylated, and the phosphorylated form then binds an inhibitor protein. Recent results indicate that the phosphorylation reaction is Ca2+-dependent and that the inhibitor is a member of the 14-3-3 family of proteins. These results suggest the convergence of several signal transduction pathways in the control of nitrate assimilation. Recent results also implicate metabolites and 5′-AMP as possible effectors regulating the phosphorylation status of NR in vivo.
The combination of two sets of molecular tools, namely yeast expression cloning and the possibility of constructing transgenic
plants, has allowed analysis of the transport processes occurring at the plasma membrane in higher plants. To date, more than
30 different plant genes for plasma membrane transporters of sugars and amino acids have been identified, mainly by expression
cloning. Furthermore, the functional expression of genes in Schizosaccharomyces pombe, Saccharomyces cerevisiae and Xenopus oocytes has been applied to obtain detailed information on the biochemical properties of the transporters. The expression
systems have also allowed the purification of the proteins for structural analysis and to study structure-function relationship
using mutagenesis approaches. A number of mutants and transgenic plants defective in certain transport properties are available
and these will help in understanding the physiology of the long-distance transport of assimilates.
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
The measurement of nitrate reductase activity in intact plant tissue based on reduction of nitrate to nitrite is facilitated by the use of propanol and other organic solvents added to the incubation medium. Optimum conditions for the assay are defined for use with soybean leaf tissue.
