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Increased Oxygen Bioavailability Improved Vigor and Germination of Aged Vegetable Seeds
Abstract
Large and/or aged seeds are prone to hypoxic conditions during germination. Germination of selected vegetable seeds including corn (Zea mays L.), squash (Cucurbita pepo L.), and tomato (Solanum lycopersicum L.) was studied in water with different concentrations of hydrogen peroxide (H2O2) solution ranging from 0, 0. 06% to 3. 0% (v/v) or in aeroponics, all with 0. 5 mM CaSO4. Imbibition, oxygen consumption, proton extrusion, and alcohol dehydrogenase (ADHase) activity of corn seeds were measured gravimetrically, electrochemically, and colorimetrically as appropriate. The results showed that 0. 15% H2O2provided the optimum oxygen concentration for seed germination. The germination percentage of aged corn seeds treated with H2O2 was significantly greater than those without H2O2 treatment. Corn embryo orientation in relation to a moist substrate also significantly impacted oxygen bioavailability to the embryo and hence ADHase activity. Corn seeds without H2O2imbibed significantly more slowly than those with oxygen fortification by 0. 15% H2O2. Increased oxygen bioavailability improved the metabolism of the seeds, which extruded 5-fold more protons from the embryos. Each treated embryo consumed twice the amount of oxygenas compared with the untreated one and likewise for treated and untreated endosperms. Increased oxygen bioavailability may be used to improve production of the tested crops. The results from this research imply that consideration should be given to including oxygen fortification in seed coatings for aged seeds and for large seeds regardless of age. The artificial provision of bioavailable oxygen might be effective in rescuing the germplasm in aged seeds in plant breeding and in crop production.
... An early study by Narimanov (2000) reported enhanced germination, emergence and development of seedlings using a short seed soaking treatment with H2O2 in a wide variety of crops including corn (Zea mays L.), beans (Phaseolus sp.), melon (Citrullus lanatus), radish (Raphanus sativa) and carrots (Daucus carota). Liu et al. (2012) tested 24-h seed pre-treatments with H2O2 with 50 mM being optimal with improved seed germination, seedling vigour and growth in corn, squash (Cucurbita pepo L.) and tomato (Solanum lycopersicum L.). Increased germination and seedling growth of peas (Pisum sativum L. 'Alaska') was shown by Barba-Espin et al. (2010) from pre-treatment of seed with H2O2. ...
... H2O2 increases germination rates by breaking down the seed coat, thus allowing the seed to take in oxygen more quickly. Liu et al. (2012) showed that the effect of H2O2 on corn seed germination was significantly greater than for seed treated with aerated water but no H2O2. Wojtyla et al. (2016) also suggested that H2O2 molecules play dual roles in plant physiological and developmental processes. ...
... In addition, oxygen consumption rates of seeds soaked for 24 hours in the H2O2 solution were approximately twice as high as seeds soaked in aerated water for the same time (Liu et al., 2012). The enhanced effects on germination with H2O2 have a) been reported for seed with pathogenic infestations (Szopniska, 2014) i.e. a biocidal effect, and b) mediated through the oxidation of germination inhibitors present in the seed coat or/and in the pericarp, i.e. a seed treatment effect. ...
The use of hydrogen peroxide (H2O2) is recently recommended for use in drip irrigation particularly for cleaning of drip emitters. Relatively less known are the effects of H2O2 in irrigation water on seed germination, seedling growth and establishment. We evaluated two hydrogen peroxide products, with varying levels of stabiliser, over a range of peroxide concentrations (10-5000 ppm), in-vitro (petri dishes) seed germination and seedling growth for ten crop species. Germination of the tested seed species was not impacted negatively by H2O2 concentrations up to 5000 ppm. Positive effects on seed germination were found for mung bean, egg plants, okra, leek and rocket at H2O2 100 ppm. Root and shoot growth were impacted more negatively by H2O2 treatments particularly at higher concentrations and for the highly stabilised H2O2 product in all crops except for corn, which is likely due to persistence of peroxide in the germination media for longer duration with stabilised H2O2 product. We conclude that stabilised H2O2 products up to 1000 ppm do not negatively impact seed germination in general and improve seed germination in some species. Negative impacts on root and shoot growth were largely associated with higher concentrations (1000 and 50000 ppm) and for some species root and shoot growth were enhanced by stabilised H2O2 at lower concentrations. Therefore, continuous injection of H2O2 at lower concentrations in irrigation water for the field crop is unlikely to negatively impact the seed germination and seedling growth.
... In the case of rare or experimental germplasm that may have been compromised by sub-optimal storage (high temperatures or humidity), the development of methodologies to revive even a bit of these materials could prove to be extremely valuable. Viability is markedly reduced in old and/or sub-optimally stored seeds due to depleted energy, low enzyme levels and hypoxic conditions during germination [14]. In such cases, intervention measures aimed at providing missing elements are necessary to achieve germination. ...
... In such cases, intervention measures aimed at providing missing elements are necessary to achieve germination. For instance, Liu, et al. [14] successfully germinated 4-year-old squash (C. pepo) seeds using hydrogen peroxide as a source of bioavailable oxygen. ...
... Hydrogen peroxide was used as a source of bioavailable oxygen during germination according to protocols developed by Liu, et al. [14]. Briefly, fifty seeds of each gellan gum (Caisson Laboratories, Smithfield, UT, USA) was added to the media for SR-G and SR-GT treatments, and then autoclaved. ...
Plant seed is both an important food source and an indispensable propagation material for many cultivated crop species. The ideal conditions required for long-term storage of seeds are expensive, exacting, and not always tenable, particularly for small breeding programs. In most plant species, viability is significantly reduced in old, sub-optimally stored seeds due to depleted energy reserves and biochemical degradation. However, revival of
such old germplasm is often desirable for research and germplasm improvement purposes. In the current study, germination response of eighteen 20-year-old squash (Cucurbita pepo L.) breeding lines was investigated in potting mix, water fortified with hydrogen peroxide, and in vitro in squash rescue (SR) medium. For the in vitro method, SR medium was delivered either as a gel (with or without a towel) or as liquid. No germination was observed in the hydrogen peroxide treatment, while only one seedling emerged in the potting mix. However, for the in vitro method, significant differences (P < 0.05) in germination rates (0-92.2%) were observed among the accessions with 33B, S347, S421, PKC2116 and Z153 showing the highest overall germination. No significant differences in germination rates were observed among in vitro treatments (gel or liquid). The current study demonstrates usefulness of SR medium in breeding projects using old, rare and valuable squash germplasm.
... Rapid seed germination and stand establishment are critical factors affecting crop production under adverse environment (Rehman et al., 2015;Ibrahim, 2016) and high seed germination is prerequisite for successful commercial crop production (Liu et al., 2012). In traditional agriculture in Asian countries, most farmers prefer to use direct-seeding method for planting important crops (Wang et al., 2016). ...
... In traditional agriculture in Asian countries, most farmers prefer to use direct-seeding method for planting important crops (Wang et al., 2016). However, direct-seeding is not effective when growing seeds under adverse environment (Zheng et al., 2015) and the use of aged seeds reduce not only the uniformity of germination and seedling establishment, but also consequently reduce agronomic productivity (Liu et al., 2012). Therefore, to improve germination and vigor of seeds, "seed priming" technique has been introduced for agricultural applications (Paparella et al., 2015). ...
... Seeds were taken out from storage in 2013 and kept at ambient temperature for 2 years to further make them naturally aged. Seed quality was tested using Petri dish assay (Liu et al., 2012) and the germination rate was found to be below 60% (data not shown) implying that these seed lots were of low quality and unacceptable by Thai Seed Quality and seed companies. ...
Application of nanotechnology in agriculture is moving towards to improve the cultivation and growth of crop plants. The present study is the first attempt to propose a simple, yet cost-effective and ecofriendly synthesis of phytochemicals-capped GNPs using rhizome extract of galanga plant at room temperature. The synthesized GNPs were characterized by various characterization techniques. To promote the green nanotechnology applications in agriculture, GNPs solution at environmentally realistic dose (5 to 15ppm) as nanopriming agent was used to activate the germination and early seedling growth of maize aged seeds. Priming with 5ppm GNPs showed the best effects on promoting emergence percentage (83%) compared to unprimed control (43%) and hydroprimed groups (56%). Seed priming at both 5 and 10ppm GNPs also enhanced seedling vigor index by 3 times over the control. Priming with GNPs at 10ppm was found to enhance the best physiological and biochemical properties of maize seedlings. Internalization studies by inductively coupled plasma atomic emission spectroscopy (ICP-OES) and transmission electron microscopy (TEM) strongly supported that GNPs can internalize into seeds. However, ICP-OES analysis revealed that GNPs were not present in both shoot and root parts, suggesting that nanopriming approach minimizes the Au translocation from seeds into plant vegetative organs. Phytosynthesized GNPs were found to be less toxic than chemically synthesized GNPs. This is the first report showing phytochemicals-capped GNPs as a promising nanopriming agent for activating the germination of naturally aged seeds of crop plant.
... Under aerobic conditions, oxygen-as an electron acceptor-is sufficient for oxidative respiration and no ADHase is needed (Irfan et al., 2010). However, sufficient O 2 for aerobic respiration is not available when corn seedlings are flooded (Liu et al., 2012a). Under flooded or other hypoxic conditions, corn seedlings may become modified anatomically by developing aerenchyma that deliver O 2 from exposed leaves to flooded parts (Bailey-Serres and Voesenek, 2008;Drew et al., 2000), or shifting from aerobic to anaerobic glycolysis, i.e., fermentation. ...
... The tank was covered with a 5 mm thick plastic sheet containing 60 evenlỳ spaced holes each with a 48 mm diameter. Sixty plastic baskets (each 50 mm high with an external diameter of 55 mm at the top and 37 mm at the bottom) were suspended in the space above the solution (Liu et al., 2012a). Two corn seeds were placed into each basket. ...
... A unit of ADHase is defined as the production of 1 nmol of NADH (mg protein × min) -1 . The activity was calculated using a value of 6.22 mM -1 cm -1 as the molar extinction coefficient of NADH at 340 nm (Liu et al., 2012a;Schomburg et al., 2012). ...
Flooding/waterlogging is a major factor responsible for hypoxic stress in agriculture. The aim of this study was to develop an effective oxygen buffer with magnesium peroxide (MgO2) to generate hydrogen peroxide (H2O2) and release bioavailable oxygen. MgO2 provided a relatively stable level (approx. 300 µM) of bioavailable oxygen. The oxygen-buffer system is adjustable and controllable by adding Mg2+ or EDTA to the aqueous system. Regular H2O2 was also able to provide bioavailable oxygen but the system was poorly buffered with respect to oxygen release. The accessibility of plants to bioavailable oxygen was indicated by the activity of alcohol dehydrogenase (ADHase, EC 1.1.1.1), an anaerobically induced enzyme of flooded plants. The application of MgO2 to flooded soil reduced ADHase activity in corn-root tips by 91.3%. This application of MgO2 presents a novel pathway to significantly (P < 5%) minimize adverse impacts of hypoxia on flooded corn seedlings. This finding may have broad implications for addressing hypoxicity problems in crop science and technology.
... H 2 O 2 is the major ROS type that is considered a signaling molecule during seed germination [25]. H 2 O 2 provides the optimum oxygen concentration for faster imbibition and germination [78]. The peak of H 2 O 2 detected at the 4th and 6th WAIs in sycamore and Norway maple seeds, respectively, possibly reflects the signaling function in the early stages of dormancy disruption. ...
... The level of H 2 O 2 release was measured according to the method described by Schopfer et al. [78]. Seeds were incubated in 1.2 mL of a solution containing 20 mM phosphate buffer (pH 6), 5 µM scopoletin and 1 U mL −1 peroxidase. ...
The levels of methionine sulfoxide (MetO) and the abundances of methionine sulfoxide reductases (Msrs) were reported as important for the desiccation tolerance of Acer seeds. To determine whether the MetO/Msrs system is related to reactive oxygen species (ROS) and involved in the regulation of germination in orthodox and recalcitrant seeds, Norway maple and sycamore were investigated. Changes in water content, MetO content, the abundance of MsrB1 and MsrB2 in relation to ROS content and the activity of reductases depending on nicotinamide adenine dinucleotides were monitored. Acer seeds differed in germination speed—substantially higher in sycamore—hydration dynamics, levels of hydrogen peroxide, superoxide anion radicals (O2•−) and hydroxyl radicals (•OH), which exhibited peaks at different stages of germination. The MetO level dynamically changed, particularly in sycamore embryonic axes, where it was positively correlated with the levels of O2•− and the abundance of MsrB1 and negatively with the levels of •OH and the abundance of MsrB2. The MsrB2 abundance increased upon sycamore germination; in contrast, it markedly decreased in Norway maple. We propose that the ROS–MetO–Msr redox system, allowing balanced Met redox homeostasis, participates in the germination process in sycamore, which is characterized by a much higher speed compared to Norway maple.
... Further examination of the outer layer by EDS revealed that it contained significantly more calcium and oxygencontaining compounds than the internal parts of the seed coat. Calcium is essential to the stability of the structure, while oxygen plays a crucial role in seed germination and seedling establishment (Liu et al. 2012;Naylor and Prentice 1986). At the same time, water is a barrier to oxygen diffusion, and seed vigor is reduced by excess water in the soil, for example, during long periods of rainfall or flooding (Liu et al. 2012;Naylor and Prentice 1986). ...
... Calcium is essential to the stability of the structure, while oxygen plays a crucial role in seed germination and seedling establishment (Liu et al. 2012;Naylor and Prentice 1986). At the same time, water is a barrier to oxygen diffusion, and seed vigor is reduced by excess water in the soil, for example, during long periods of rainfall or flooding (Liu et al. 2012;Naylor and Prentice 1986). Thus, it can be assumed that the outer layer of seeds of the studied Impatiens species, in which the levels of calcium and oxygen were high, may also protect the seeds during floating, as the seeds may persist in good conditions even after long periods of submergence in water. ...
Two alien species in Europe, Impatiens glandulifera and I. balfourii, are closely related, have similar growth rates and reproductive capacities, and are very attractive to pollinators. Nevertheless, only I. glandulifera is a highly invasive alien species in Europe, while I. balfourii is non-invasive. We assumed that the varying levels of invasiveness are driven by differences in the floating ability of their seeds, which may determine the invasion success of riparian alien plants, such as the Impatiens species. By mimicking two types of aquatic conditions, we determined seed floating ability for each species from younger and older populations. We also analyzed four seed traits: seed viability, surface, shape and coat structure. Seeds of the non-invasive I. balfourii float less well than seeds of the invasive I. glandulifera. We also found that the seeds of I. balfourii from the younger population have a higher floating ability in comparison with that of the seeds from the older population. The results for I. glandulifera were the opposite, with decreased floating ability in the younger population. These differences were associated with seed surface, shape and coat structure. These results indicate that the floating ability of I. balfourii seeds may increase over time following its introduction into a given area, while in the case of I. glandulifera, this ability may gradually decrease. Therefore, the former species, currently regarded as a poor disperser, has the potential to become invasive in the future, whereas the latter does not seem to benefit from further investments in the floating ability of its seeds.
... Chemical oxygen fertilization of the root zone, with slow release (solid) formulations such as calcium peroxide (CaO 2 ) or magnesium peroxide (MgO 2 ), or fast release (liquid) formulations such as hydrogen peroxide (H 2 O 2 ) or carbamide peroxide (CH 4 N 2 O·H 2 O 2 ), is a potential method of alleviating root hypoxia (Liu and Porterfield, 2014;Liu et al., 2012Liu et al., , 2013. Injecting H 2 O 2 into the irrigation water increased oxygen in the soil (Gil et al., 2009a) as well as water use efficiency and biomass of avocado (Gil et al., 2009a). ...
... After a reaction time of 1 min, NADH concentration in the cuvette was determined with a Beckman DU-640 Spectrophotometer (Beckman Instruments, Fullerton, California, USA) at an absorbance of 340 nm. ADH activity was calculated as an average from 5 single-plant replicates using a value of 6.22 mM −1 cm −1 as the molar extinction coefficient of NADH (Liu et al., 2012;Schomburg et al., 2012). Protein content of the extract was determined based on the Bradford assay using a protein assay kit (Bio-Rad Laboratories, Hercules, CA, USA). ...
... Chemical oxygen fertilization of the root zone, with slow release (solid) formulations such as calcium peroxide (CaO 2 ) or magnesium peroxide (MgO 2 ), or fast release (liquid) formulations such as hydrogen peroxide (H 2 O 2 ) or carbamide peroxide (CH 4 N 2 O·H 2 O 2 ), is a potential method of alleviating root hypoxia (Liu and Porterfield, 2014;Liu et al., 2012Liu et al., , 2013. Injecting H 2 O 2 into the irrigation water increased oxygen in the soil (Gil et al., 2009a) as well as water use efficiency and biomass of avocado (Gil et al., 2009a). ...
... After a reaction time of 1 min, NADH concentration in the cuvette was determined with a Beckman DU-640 Spectrophotometer (Beckman Instruments, Fullerton, California, USA) at an absorbance of 340 nm. ADH activity was calculated as an average from 5 single-plant replicates using a value of 6.22 mM −1 cm −1 as the molar extinction coefficient of NADH (Liu et al., 2012;Schomburg et al., 2012). Protein content of the extract was determined based on the Bradford assay using a protein assay kit (Bio-Rad Laboratories, Hercules, CA, USA). ...
In many parts of the world papaya (Carica papaya L.) is prone to hypoxic stress due to soil flooding as a result of severe storms or hurricanes. Two experiments were conducted to test the effects of root zone hypoxia on physiology, recovery and survival of papaya and to determine if negative impacts of root hypoxia can be reduced by chemically enriching the root zone with oxygen. In Experiment 1, seedlings in soil were divided into three flooding treatments: (1) 100% of roots submerged, (2) ∼75% of roots submerged, or (3) non-flooded; and three oxygen fertilization treatments: (1) 0 g CaO2, (2) 2.28 g CaO2, or (3) 4.57 g CaO2 applied to the soil prior to flooding. In soil, CaO2 is broken down to H2O2which then releases oxygen to the rhizosphere. Therefore, in Experiment 2, plants in a hydroponic solution were divided into six treatments: (1) aeration of the hydroponic solution and no H2O2 added to the solution, (2) no aeration and no H2O 2added; (3) no aeration and 200 l of 3% H2O2 l−1added daily, (4) no aeration and 500 l of 3% H2O2 l−1added daily, (5) no aeration and 1000 l of 3% H2O2 l−1 added daily, or (6) no aeration and 2000 l of 3% H2O2l−1added daily. In soil, flooding of ∼75% or 100% of roots for two days decreased net CO2 assimilation (A), stomatal conductance (gs), the leaf chlorophyll index, and the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm). After plants were unflooded, these variables recovered to levels similar to those of the non-flooded treatment for plants with ∼75% of the roots submerged but did not recover in plants with 100% of the roots submerged if no CaO2 was applied to the soil. If 2.28 or 4.57 g of CaO2 was applied to the soil, A, gs, leaf chlorophyll index, and Fv/Fm recovered to values similar to those of non-flooded plants. Addition of CaO2 to the soil also minimized reductions in leaf, stem, root and plant dry weights and increased survival of plants with 100% of roots submerged. For plants in the hydroponic solution, A and gs were generally lower in the non-aerated treatments than in the aerated treatment. If 500 or 1000 l H2O2 l−1 was added to the solution, A of plants in the non-aerated solution tended to recover to levels similar to those of plants in the aerated solution. Root ADH activity ended to be greater in the non-aerated treatment with no H2O2 added to the solution than in any of the treatments with H2O2 added. This study demonstrated that chemical oxygen enrichment of the root zone reduces flooding stress and increases recovery and post-flooding survival of papaya.
... To eliminate external pathogens, seeds were surface sterilized by 70% ethanol for 30 seconds, followed by 1% sodium hypochlorite for 10 min. [21], and CaSO 4 (0.5 mM) was added to protect the membrane; whereas, aged seeds have very fragile biological membranes [22]. 2. For improving vigor and softening of old seeds, the seeds obtained from the previous step were divided into two groups; group one: seeds were rinsed four times with sterile distilled water, allowing 5 min for each rinse. ...
The deterioration of the viability of seeds of old varieties (heirloom varieties) by exposure to long storage periods is one of the main problems facing plant breeding programmes; Thus, oxygen bioavailability and somatic embryogenesis techniques can overcome this problem to some extent. The goals of this study were to: 1) define the optimal oxygen bioavailability concentration for increasing the germination rates of old and waterlogged seeds; 2) define the relationship between the concentration of bioavailable oxygen in the liquid ingested by the germinating seed and seed vigor; and 3) use somatic embryogenesis techniques as a method for recovering plant germplasm from old or improperly stored seeds for use in plant breeding programs. This study was conducted in the tissue culture laboratory of the Potato and Vegetatively Propagated Vegetables Department, Horticulture Research Institute, Agricultural Research Centre, Egypt. This research was conducted to regenerate perennial seeds (8 years) of common bean (Phaseolus vulgaris L.) variety Giza 6 (local variety) and compared with 1 year old seeds as control treatment of the same cultivar. This study established that prolonged hypoxia throughout a protracted period of storage can inhibit germination. Hypoxia during the impregnation and germination of bean seeds can be overcome by supplying the seeds with hydrogen peroxide (20 mM) throughout the germination process. Catalase enzyme (10.5 units/mL) is needed to convert hydrogen peroxide into oxygen. Also, to release oxygen from hydrogen peroxide, other catalytic agents, such as transition metal ions like Fe+2, Cu+2, and Mn+2, can be used at the following concentrations: 0.001M, 0.001M, and 0.0001M, respectively. A protective layer of CaSO4 (0.5 mM) was applied since aged seeds have very fragile biological membranes. The test of tetrazolium gave results for some seeds that it non-viable or some parts of the seed are damaged or defective; However, 2,4-D at a concentration of 5 mg/l + supplements (0.1 µM GA3/L + 2 mg kintien/L + 1.0 mM glutamine) was able to produce somatic embryos of the old seeds tissues for common bean cv. Giza 6 (a local variety). The study of the morphology and induction of somatic embryogenesis was done used scanning electron microscopy. In its early phases, the callus appeared as a scattering of elongated cells. And after being transferred to the DCR medium, the cells became tightly packed together, and globular-shaped embryos began to emerge between the tightly packed together cells.
... Since large seeds require more water for normal metabolism, they are more easily damaged by reduced osmotic potential [52]. Moreover, Liu et al. stated that large seeds are more prone to oxygen deficits in the soil to support their germination [53]. Furthermore, large seeds also would likely encounter more physical resistance from soil restricting cotyledons during emergence. ...
Vegetable soybean or edamame is a specialty soybean (Glycine max (L.) Merr.). Unlike grain-type soybean (mainly for oil and source of protein in animal feeds), edamame pods are harvested at a green and immature stage, and beans are consumed by humans as a vegetable. While originally from China, edamame has recently gained much-increased popularity and expanded market needs in the US. However, domestic edamame production is limited in the US because at least 70% of the edamame consumed is imported. Poor seed germination and seedling emergence are one of the major problems in US edamame production. This review focuses on the introduction of edamame, a high-value niche crop, and its low emergence issue in production. Here, we provide a comprehensive exploration of the factors that influence edamame germination and emergence, including the intrinsic factors related to seeds (seed and seedling characteristics), and extrinsic factors related to the biotic (soil/seed-borne diseases) and abiotic (seedbed physical components as well as their interaction with climate) stresses. This information will help farmers and plant breeders to better understand the causes of the poor edamame emergence and may provide a foundation for improved field management of edamame, to increase production of this valuable specialty crop.
... 12,000 g for 15 min at 4 °C in a refrigerated centrifuge (Chung and Ferl 1999) and the supernatant was collected and used immediately for enzyme activity assays. The spectrophotometric measurements of the reduction of NAD to NADH in the presence of ethanol substrate were used to quantify differences in ADH activity among genotypes in flooding and nonflooding environments by applying a modified version of methods described by Chung and Ferl (1999) and Liu et al. (2012). A 50 μL of enzyme extract and 900 μL of reaction solution composed of 50 mM Tris-HCl (pH 8.0) and 1 mM NAD were incubated in microcentrifuge tubes in a water bath at 30 °C for 3 min. ...
Background and aimsThere is little information about the role of fungal endophytes on plant performance under oxygen-limited conditions. This study aimed to investigate the effect of Epichloë endophyte symbiosis on tall fescue responses to oxygen stress in a greenhouse experiment.Methods
The experiment was conducted with seven air-filled porosity levels in a sandy loam soil using genotypes (75C and 75B) of tall fescue (Festuca arundinacea) infected with and without endophytic fungus Epichlöe coenophiala (E+ and E–, respectively). Growth and physiological variables were determined to characterize plant response to oxygen-limited conditions, after nine-month application of the treatments.ResultsThe results showed that E+ 75B plants benefited from endophytic symbiosis in all air-filled porosity levels, showing a higher plant biomass, better water status and lower catalase and ascorbate peroxidase activity than E– 75B plants. In contrast, a reverse trend was observed for the genotype 75C. The E– plants also coped with poor aeration by forming adventitious roots at the soil surface, aerenchyma formation within the root tissue, and increased alcohol dehydrogenase activity.Conclusions
The presence of endophyte improved the genotype 75B performance under anaerobic conditions, while endophyte had an adverse effect on the performance of genotype 75C. This is probably due to incompatibility between Epichlöe endophyte and genotype 75C. Epichloë endophyte is likely to decrease the flooding-induced oxidative stress and prevented the over-accumulation of reactive oxygen species in the genotype 75B. Epichloë endophyte probably maintained oxidative conditions around the roots, and consequently, E+ plants required lower level of flooding-tolerance mechanisms.
... Finally, it is important to mention that stimulation and inhibition results are observed for treated SFCWW by H 2 O 2 /solar and chlorination (100 mg/L) processes, respectively. The stimulation effect (RGI value > 1.2) observed after the H 2 O 2 /solar process could be due to the presence of a high residual H 2 O 2 concentration (13 mg/L) that could act in different ways: 1) providing protection from potential microbial infections; 2) weakening the endosperm cap accelerating the seed germination process (Wojtyla et al., 2016) and; 3) generating additional oxygenation to the seedling after its decomposition (Liu et al., 2012). The inhibition effect showed by the chlorinated SFCWW can be due to both, the presence of residual chlorine and/or toxic chlorinated DBPs (Lonigro et al., 2017). ...
In this study, a full cycle of agricultural reuse of agro-food wastewater (synthetic fresh-cut wastewater, SFCWW) at pilot plant scale has been investigated. Treated SFCWW by ozonation and two solar processes (H2O2/solar, Fe³⁺-EDDHA/H2O2/solar) was used to irrigate two raw-eaten crops (lettuce and radish) grown in peat. Two foodborne pathogens (E. coli O157:H7 and Salmonella enteritidis) and five organic microcontaminants (OMCs: atrazine, azoxystrobin, buprofezin, procymidone and terbutryn) were monitored along the whole process. The three studied processes showed a high treatment capability (reaching microbial loads < 7 CFU/100 mL and 21-90 % of OMC reduction), robustness (based on 7 or 10 analysed batches for each treatment process) and high suitability for subsequent treated SFCWW safe reuse: non-phytotoxic towards Lactuca sativa and no bacterial regrowth during its storage for a week. The analysis of the harvested crop samples irrigated with treated SFCWW in all the studied processes showed an absence of microbial contamination (< limit of detection, LOD; i.e., < 1 CFU/99 g of lettuce and < 1 CFU/8 g of radish), and a significant reduction of OMCs uptake (in the range of 40-60 % and > 90 % for solar treated and ozonated SFCWW, respectively) and bioaccumulation in both crops in comparison with the results obtained with untreated SFCWW. Moreover, the chlorophyll content in the harvested lettuces irrigated with SFCWW treated by Fe³⁺-EDDHA/H2O2/solar was twice than that irrigated with SFCWW treated by H2O2/solar and ozone, indicating the additional advantage of using Fe³⁺-EDDHA as an iron source to reduce the risk of iron chlorosis. Finally, the chemical (dietary risk assessment for the combined exposure of the 5 OMCs) and quantitative microbiological risk assessment (QMRA) of the harvested crops showed the capability of the studied processes to reduce the risk associated with to untreated SFCWW reuse by more than 50 % and more than 4 orders of magnitude, respectively.
... The distinct type, size, shape, and dose of nanoparticles have peculiar direct or indirect effect on the seed quality parameters, such as germination percentage, seedling length, seedling dry weight, and seed vigor indices (Monica and Cremonini 2009). However, most of the current publications regarding nanoparticles and crops are centered around the effects of nanoparticles on seed germination and other quality parameters (Stampoulis et al. 2009), as rapid germination and establishment of seedling are the most crucial factors, which affects the crop production (ur Rehman et al. 2015;Ibrahim 2016;Liu et al. 2012). Moreover, Opoku et al. (1996) stated that seeds with better germination cause vigorous growth of plant and robust root system (Opoku et al. 1996). ...
The increasing population of the world requires novel techniques to feed everyone, which can replace or work along with traditional methods to increase production of agricultural crops. In recent times, nanotechnology is considered as a promising and emerging approach to be incorporated in agriculture to improve productivity of different crops by the administration of nanoparticles through seed treatment, foliar spray on plants, nano-fertilizers for balanced crop nutrition, nano-herbicides for effective weed control, nanoinsecticides for plant protection, early detection of plant diseases and nutrient deficiencies using diagnostics kits, and nano-pheromones for effective monitoring of pests. Further, distinct nanoparticles with unique physicochemical and biological properties are used in agriculture to increase the percentage of seed germination, which is the initial step to increase the crop yield. In the context of agricultural crops, nanoparticles have both positive effects on seed quality parameters, such as germination percentage, seedling length, seedling dry weight and vigor indices, as well as negative impacts of causing toxicity toward the environment. Thus, the aim of this review article is to provide a comprehensive overview on the effects of super-dispersive metal powders, such as zinc, silver, and titanium nanoparticles on the seed quality parameters of different crops. In addition, the drawback of conventional seed growth enhancers, impact of metal nanoparticles toward seeds, and mechanism of nanoparticles to increase seed germination were also discussed.
... The spectrophotometric measurements of the reduction of NAD to NADH in the presence of ethanol substrate were used to quantify differences in ADH activity among genotypes in ooding and non-ooding environments by applying a modi ed version of methods described by Chung and Ferl (1999) and Liu et al. (2012). A 50 µL of enzyme extract and 900 µL of reaction solution composed of 50 mM Tris-HCl (pH 8.0) and 1 mM NAD were incubated in microcentrifuge tubes in a water bath at 30°C for 3 min. ...
Background and aims There is little information about the effect of grass-fungal endophyte symbiota on plant performance under oxygen-limited conditions. This study aimed to investigate the effect of Epichloë endophyte symbiosis and tall fescue genotype on plant responses to oxygen stress in a greenhouse pot experiment.
Methods A greenhouse pot experiment was conducted with seven air-filled porosity levels in a sandy loam soil using two genotypes (75C and 75B) of tall fescue (Festuca arundinacea = Schedonorus arundinaceus Schreb.) infected with and without endophytic fungus Epichlöe coenophiala (E+ and E–, respectively). Some selected growth and physiological parameters were determined after nine-month application of the treatments.
Results The results showed that E+ plants benefited from endophytic symbiosis and showed slightly higher root and shoot development, more leaf chlorophyll, and lower catalase and ascorbate peroxidase activity than E– plants under poor aeration. The E– plants also coped with poor aeration conditions by forming adventitious roots at the soil surface, aerenchyma formation within the root tissue, and increased alcohol dehydrogenase (ADH) activity.
Conclusions The presence of endophyte improved the performance of the genotype E+ 75B under anaerobic conditions, while endophyte had an adverse effect on the performance of the genotype E+ 75C. In general, Epichloë endophyte presence decreased the flooding induced oxidative stress and prevented the formation and over-accumulation of reactive oxygen species in plant cells.
... Therefore, it is important to study seed aging for protecting germplasm resources and maintaining crop yield and quality. Seed aging is an irreversible and gradual change process which involves many physiological and biochemical reactions, such as membrane lipid peroxidation, changes in protective enzymatic activity, accumulation of toxic and harmful substances, protein and nucleic acid metabolism, and endogenous hormones (Murthy et al. 2000;Liu et al. 2012;Parkhey et al. 2012;Ratajczak et al. 2015). Until now, various academic viewpoints have already explained the aging mechanism from different perspectives (Kalemba et al. 2014;Spanò et al. 2007;Kranner et al. 2011;Bachem et al. 1996), while the transcription level on seed aging mechanism is unclear. ...
Sugarcane growth is negatively affected by abiotic stresses. Genetic engineering of sugarcane with abiotic stress-responsive genes has been the method of choice to confer abiotic stress tolerance. In the present work, we optimized callus induction and transformation of the sugarcane variety CP-77-400 with the promoter region of the OsC3H52 gene to analyze its regulatory function under drought and salt stress. Calli were induced using different callus induction media (CIM). The promoter region of the OsC3H52 gene that belongs to the zinc finger protein family was cloned into two different expression vectors i.e. pBI221 and pGreenII0129, which were subsequently transformed to sugarcane calli through agrobacterium and biolistic transformation methods. Among various callus induction media, CIM3 (5 mg L-1 2,4-D + 10% coconut water) showed high callus induction (93%). Biolistic transformation using recombinant pGreenII0129 at 8.5µg/µl concentration resulted in higher efficiency of transformation (28%). While the agrobacterium mediated transformation using recombinant pBI221 plasmid gave 13% transformation efficiency. Amongst the various concentrations of acetosyringone used in agrobacterium mediated transformation, 100 µM showed higher efficiencies (13%) of transformation. Selection of the transformed calli was performed at 25 mg L-1 Hygromycin and 25 mg L-1 Hygromycin + 300 mg L-1 cefotaxime for 15 days, both for biolistic and agrobacterium mediated transformation, respectively. Transformed calli were then successfully confirmed through PCR and GUS expression. The regulatory role of the OsC3H52 promoter in transgenic calli was further evaluated under drought and salt stress. Quantitative real-time PCR analysis of the GUS reporter gene showed high expression in transgenic calli under drought and salt stress conditions.
... Poor seed germination and slow post germination growth are the characteristic features of aged seeds (Guodong Lui et al., 2012). Aged seeds also possess low plasma membrane H + -ATPase activity and partially explain poor germination and low post germination root elongation and growth of seedling development (Sveinsdottir et al., 2008) as observed in our study. ...
p > Application of nanotechnology in agriculture aims to reduce the usage of plant protection products, improve the cultivation and increase the growth and yield of crop plants. The present study is the first attempt to biosynthesize a simple, cost-effective and eco-friendly phytochemically capped AgNPs using < em > Psophocarpustetragonolobus (winged bean) leaf extract. The biosynthesized AgNPs were confirmed by UV-Vis spectrophotometer with Surface Plasmon Resonance at 430 nm. The XRD pattern and EDAX spectrum were confirmed the crystalline nature of biosynthesized AgNPs. Fourier transform infrared (FTIR) was confirmed the presence of polyphenols and an aromatic group of protein played an important role in the reduction of AgNO3 to AgNPs. < st1:stockticker w:st="on">TEM and AFM analysis were confirmed the size of biosynthesized AgNPs was 15.47 to 20.98 nm. Seed priming is a technique which involves uptake of water by the seed followed by the benefits includes rapid, uniform and increased germination, improved seedling vigor and growth under a broad range of environments resulting in better stand establishment and alleviation of phytochromeinduced dormancy in some crops. Winged bean seeds primed with photosynthesized AgNPs50 significantly improved germination percentage (88.33%), vigor index (2848.44) as compared to hydroprimed and unprimed control. Moreover, AgNPs could enhance antioxidant enzymes like peroxidase, catalase, ascorbate peroxidase and superoxide dismutase and a higher concentration of soluble sugar, soluble protein, sucrose and chlorophyll contents supporting the seedling growth. Furthermore, ISSR markers confirmed the genetic uniformity of nanopriming with AgNPs and the seedling showed normal phenotypical characters without any toxicity.It was concluded that AgNP50 was the best nanopriming treatment to enhance the germinability, enzymes and biochemical activities in < font color="#0782c1"> P.tetragonolobus. < /i> </p
... ( ،ﺑﺬر ﻗﺪرت اوﻟ ﯿ ﻦ ﮐ ﺟﺰء ﯿ ﻔ ﯿ ﺖ ﻃ ﮐﻪ اﺳﺖ ﺑﺬر ﯽ ﻣ دﺳﺖ از زوال ﯽ رود و ﻇﺮﻓ ،اداﻣﻪ در ﯿ ﺖ ﺟﻮاﻧﻪ زﻧ ﯽ ﻗﻮه و ﻧﺎﻣ ﯿ ﻪ ﻧ ﺑﺬر ﯿ ﺰ ﺑ از ﯿ ﻦ ﻣ ﯽ رود ) Basra et al., 2003 . ( زوال ﺑﺬور از اﺳﺘﻔﺎده ﯾ ،ﺎﻓﺘﻪ ﻧﻪ ﺗﻨﻬﺎ ﯾ ﮑﻨﻮاﺧﺘ ﯽ ﺟﻮاﻧﻪ زﻧ ﯽ ﮔ اﺳﺘﻘﺮار و ﯿ ﺎﻫﭽﻪ ﮐﺎﻫﺶ را ﻣ ﯽ ،دﻫﺪ ﮔ ﻋﻤﻠﮑﺮد ﺑﻠﮑﻪ ﯿ ﺎه زراﻋ ﯽ ﻧ را ﯿ ﺰ ﻣ ﮐﺎﻫﺶ ﯽ دﻫﺪ ) Liu et al., 2012 ( ؛ ﺑﻨﺎﺑﺮا ﯾ ،ﻦ ﺟﻬﺖ ﺟﻮاﻧﻪ ﺑﻬﺒﻮد زﻧ ﯽ و ﭘﺮا روش ،ﺑﺬور ﻗﺪرت ﯾ ﻤ ﯿ ﻨﮓ ﺑﻪ ،ﺑﺬر ﮐﺎرﺑﺮدﻫﺎ ﻣﻨﻈﻮر ي ﮐﺸﺎورز ي ﻣﻌﺮﻓ ، ﯽ اﺳﺖ ﺷﺪه ) Paparella et al., 2015 . ( ﭘﺮا ﯾ ﻤ ﯿ ﻨﮓ ﻣ ﺑﺬر ﯽ ﺗﻮاﻧﺪ ﻓﺮآ ﯾ ﻨﺪﻫﺎ ي ﻣﺘﺎﺑﻮﻟ ﯿ ﮑ ﯽ ﺑﻪ ﮐﻪ ﻃﻮر ﻃﺒ ﯿ ﻌ ﯽ ﻃ در ﯽ اوﻟ ﻓﺎز ﯿ ﻪ ﺟﻮاﻧﻪ زﻧ ﯽ ﻣ ﻓﻌﺎل ﯽ ﺷﻮﻧﺪ ﻣﻮﺟﺐ را اﻓﺰا ﻣﻮﺟﺐ اداﻣﻪ در و ﺷﻮد ﯾ ﺶ ﻣ ﯿ ﺰان ﺟﻮاﻧﻪ زﻧﯽ ﻇﻬﻮر و ﮔ ﯿ ﺎﻫﭽﻪ ﺷﻮد ) Paparella et al., 2015 . ...
Drought and salinity are major environmental factors that influence crop productivity worldwide .Plants are normally subjected to a combination of various types of abiotic stresses in nature, such as the combined effects of drought and salinity .Studies have revealed that the physiological and biochemical responses of plants to the interaction of drought and salinity are unique and cannot be directly extrapolated from the responses to the two stresses individually.
Storage of orthodox seeds for prolonged period induces their deterioration leading ultimately to loss of their viability. The rate of seed deterioration varies among plant species and seed lots, but high moisture content and high temperature accelerate this process. During long-term storage, all seeds undergo aging processes leading to deterioration in seed quality, especially in the humid tropical regions. However, the rate of seed deterioration can vary among various plant species. When aged seeds are sown, they show decreased viability, lower germinability performance, and produce weak seedlings which could not manage to survive in their habitat.
Seed priming (osmoconditioning) has been successfully demonstrated to improve seed germination and seedling establishment for many field crops.The beneficial effects of priming have also been demonstrated on germination and seed emergence, as well as seedling establishment of many crops, particularly under drought and salt stress.Use of chemical compounds as priming agents has been found to improve plant tolerance
significantly in various crop and non-crop species against a range of different individually applied abiotic stresses.Melatonin, due to its pleiotropic effects can play important roles in improving plant tolerance to adverse conditions.
Safflower (Carthamus tinctorius L.) is one of the prospective oilseed crops because it yields about 32–40 % seed oil. However, due to its considerable salt resistance than commonly grown oilseed crops, it is cultivated in arid and semi-arid regions where soil salinity is one of the major threats to agriculture.Drought is very unpredictable among abiotic stresses in terms to occurrence, severity, timing. and duration and safflower can be a promising alternate crop in dryland agro-ecosystems due to its growth potential under water stress without a substantial reduction of oil and seed yields. Safflower cultivation constitutes a more profitable crop for the farmers in some countries, compared to other conventional crops such as barley, lentil, and chickpea.The fact that safflower can overcome environmental stresses such as extreme temperatures, drought, and salinity has facilitated its expansion in areas around the world, where soil and climatic restrictions have impeded the cultivation of conventional food and cash crops.
In particular, safflower has demonstrated drought resistance with a slight decrease in crop yield and significant stability in water use efficiency
Materials and methods
In order to study the effect of seed priming of naturally aged seed by melatonin on seedling emergence and growth characteristic of safflower, three experiments were conducted at seed science technology laboratory, greenhouse and research farm of Aburaihan Campus, the University of Tehran in 2017. The experimental design for all experiment was factorial in completely randomized design (laboratory) and randomized complete block design (research farm and greenhouse) with 4 replicates. The main treatments that common between experiments consist of seed quality (1-naturally aged seed 2- new seed) and seed priming (1-without priming 2- hydropriming 3- Melatonin 0.1 mM 4- Melatonin 0.5 mM). Soil water was determined based on soil moisture release curve, which indicates the relationship between soil water potential and
soil moisture content. Prior to the pot experiments, three samples of wet soil (wet soil = dry
soil ? soil moisture content) were dried and soil moisture content at the beginning of experiment was determined.Then pots were equally filled with wet soil. Two pots were considered as references and were weighted each day: one for drought stress and one for other abiotic stresses. The soil moisture content could be obtainable after weighing and it was possible to calculate soil water potential from soil moisture release curve.
Results and discussion
The results of this research indicated that the highest percentage of seedling emergence of naturally aged seed obtained by hydropriming and melatonin priming at 0.1 mM by %54.50 and %57.50 that increased the seedling emergence up to %39.74 and %47 respectively, in comparison to control in the farm condition. Also, the results showed that highest percentage of seedling emergence under drought condition belong to melatonin priming at 0.1 mM concentration that increased the seedling emergence up to %154 in comparison to control in the greenhouse condition. The results of this experiment indicated melatonin priming at 0.1 mM concentration led to the highest rate and percentage of seedling emergence under salinity and combination of salinity and drought condition while melatonin priming at 0.5 mM concentration has decreased the rate of seedling emergence.
Conclusions
In general, using of seed priming as a cost-effective method also hydropriming and melatonin priming could enhance the seed quality for growth under salinity and drought conditions.
... 35 Low enzyme activity, declines in the antioxidant potential of the cell, and retardation of biochemical and physiological reactions causes poor germination in aged vegetable seeds. 36 Slow seed germination can expose seedlings to adverse environmental conditions, resulting in poor seedling vigor and ultimately economic losses for the growers. Seed priming can be utilized to reduce economic losses due to poor seedling emergence. ...
Green nanotechnological approach is a rapidly expanding in sustainable precision agriculture that promises to revolutionize food production. In the present study, nanoparticles (NPs) were synthesized using efficient green process involving the use of plant extracts as reducing agents. Silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) were synthesized using onion extracts and characterized by UV-vis spectrophotometry, dynamic light scattering technique, X-ray diffraction, transmission electron microscopy, and liquid chromatography–mass spectrometry. In addition, two nanoemulsions were also prepared from turmeric oil and citrus oil using a low energy method based on spontaneous emulsification. These NPs and emulsions were used for priming aged onion seeds. Internalization studies conducted by instrumental neutron activation analysis and gas chromatography-mass spectrometry revealed that the treated nanoparticles and nanoemulsions were internalized into onion seeds. Multiple greenhouse and field studies demonstrated the enhanced seed germination, emergence, growth, and yield compared with unprimed and hydroprimed seeds. Seed priming with AuNPs showed the significant change in emergence percentage (63.2%) compared to unprimed control (37.4%) during combined analysis of both year experiments. An average yield increase of 23.9% was observed in AuNPs treated onion, as compared to unprimed onion. The results of the present study provide safe and sustainable use of nanomaterials in agriculture.
... Although minor inter-and intra-species differences existed for the effect of factor B, all the greatest average root length for tall fescue 2015, the highest average GP and the activity of SOD for orchardgrass 2013, those of root length, shoot length and CAT activity for Russian wildrye 2009, as well as those of GP, SVi, root length, shoot length, the activity of SOD and CAT for tall fescue 2014 occurred in the H 2 O 2 -priming. Consistently, Liu et al. reported that H 2 O 2 priming could improve the oxygen bioavailability, imbibition rate and metabolism of aged seeds [43]. H 2 O 2 was originally recognized mainly as a reactive oxygen species that plays deleterious role in cell organization and viability. ...
Germination of seeds during the transportation or after prolonged storage naturally and inevitably decreases because of ageing, but germination potential can be partially restored with seed priming treatments. A novel attempt was made to investigate the effects of combined treatments and to optimize the conditions for naturally aged seeds of tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.) and Russian wild rye (Psathyrostachys juncea (Fisch.) Nevski) using an orthogonal activity level experimental design [factor A: Azospirillum brasilense concentration, factor B: three seed priming treatments (H2O, MgSO4 and H2O2) and factor C: different priming times]. Multivariate regression model analysis was applied to determine the interactive effects of pairwise factors (A and C) and to optimize experimental conditions. The results showed that the mixed treatments positively affected seed germination and seedling growth. The three seed priming treatments were the dominant factors for germination promotion, whereas the bacterial concentration had the largest effect on seedling growth and the activity of superoxide dismutase (SOD), especially root elongation. The malondialdehyde content was reduced, the activities of SOD, peroxidase and catalase were triggered, and ascorbate peroxidase activity was also affected by the co-treatment. The combined results of all determined attributes showed that A. brasilense bio-priming with H2O2 priming constituted the optimal combination. The optimal bacterial concentration of A. brasilense and the time of seed priming were 52.3 × 10⁶ colony forming units (CFU) mL⁻¹ and 17.0 h, respectively.
... These factors can hasten the 38 aging process of seeds [5,6] . Previous reports have shown that under ambient storage conditions in 39 eastern Serbia in 2009, the reduction in germination of Italian ryegrass (Lolium multiflorum L.) 40 and timothy (Phleum pretense L.) seeds occurred from 180 th and 330 th days after harvest, ...
Germination of seeds during the transportation or after prolonged storage naturally and inevitably decreases because of ageing, but germination potential can be partially restored with seed priming treatments. A novel attempt was made to investigate the effects of combined treatments and to optimize the conditions for naturally aged seeds of tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.) and Russian wild rye (Psathyrostachys juncea (Fisch.) Nevski) using an orthogonal activity level experimental design [factor A: Azospirillum brasilense concentration, factor B: three seed priming treatments (H2O, MgSO4 and H2O2) and factor C: different priming times]. Multivariate regression model analysis was applied to determine the interactive effects of pairwise factors (A and C) and to optimize experimental conditions. The results showed that the mixed treatments positively affected seed germination and seedling growth. The three seed priming treatments were the dominant factors for germination promotion, whereas the bacterial concentration had the largest effect on seedling growth, especially root elongation. The combined results of all determined attributes showed that A. brasilense bio-priming with H2O2 priming constituted the optimal combination. The optimal bacterial concentration of A. brasilense and the time of seed priming were 52.3 × 106 colony forming units (CFU) mL-1 and 17.0 h, respectively. We also discussed the physiological mechanisms that could repair aged seeds: the malondialdehyde content and antioxidant enzyme (superoxide dismutase, peroxidase, catalase and ascorbate peroxidase) activities were affected.
... Laboratories such as gene banks that work with dormant seeds of crops' wild relatives can benefit from concentrated O 2 gas applications to release dormancy. In addition to its use in seed dormancy release, the same apparatus could have application in the study of seed aging (Ohlrogge andKernan, 1982, Groot et al., 2012), and may provide easily manipulated biologically available O 2 gas to improve the performance of aged low-vigor seeds as an alternative to the hydrogen peroxide used by Liu et al. (2012). Indeed the increased germination we observed may be partly from increased vigor and not just dormancy release. ...
A new method is demonstrated for using concentrated oxygen (O2 gas) to release seed dormancy. Concentrated O2 gas in air is known to release seed dormancy in some seeds, including some foxtail (Setaria) species. New medical equipment makes O2 gas easier to work with than before, so laboratories working with dormant seeds can now use concentrated O2 gas as a seed treatment on a production basis. Use of medical O2 gas concentrators is simpler and safer than using O2 gas supplied by pressurized gas cylinders. Suitable medical O2 gas concentrators in new or used condition are readily available, operate on standard electrical current, and deliver O2 gas with low-pressure tubes and fittings. Resealable plastic bags are inflated with concentrated O2 gas and then sealed as seed treatment chambers. This use of concentrated O2 gas is confirmed to significantly increase the germination of dormant seeds of giant foxtail (Setaria faberi Herrm) and plains bristlegrass (S. macrostachya Kunth).
... Thus, these results suggest that hydrogen peroxide can provide oxygen under hypoxic conditions for bean seeds during imbibition and germination and can thus overcome adverse effects of hypoxia. Previous studies have shown that hydrogen peroxide can improve germination of aged seeds [26]. Similarly, hydrogen peroxide was shown to improve the germination in rice, but its role was primarily thought to be in breaking seed dormancy [9]. ...
... For soil bioremediation, many oxygen-rich peroxides which have a strong oxidizing capacity, including hydrogen peroxide, calcium peroxide and magnesium peroxide, have been studied extensively for their potential use in reclaiming these soils [13] [14]. In the case of crop plants, oxygen-rich peroxides have been used, mainly as a seed treatment, to provide oxygen and to improve crop performance in wetland rice, and to improve germination of seeds [15]- [18]. In addition, use of hydrogen peroxide has been found to improve crop performance of avocado in poorly drained soils [19]. ...
Oxygen limiting conditions are a common occurrence in root zones of most crop plants and can adversely affect nearly all aspects of plant growth and development including its survival. The ob-jective of this study was to determine the effectiveness of a novel redox cycling agent, vitamin K 3 , and various peroxides including hydrogen peroxide, calcium peroxide and magnesium peroxide in alleviating the effects of hypoxia in bean seedlings grown in nutrient culture. All the anti-hypoxic agents including vitamin K 3 had a positive impact on the overall growth of bean seedlings under hypoxic conditions, but their responses were variable depending on the concentration. With re-gard to shoot growth, vitamin K 3 (5 μM) increased the leaf area significantly, by more than 58% over the hypoxic control plants and produced the highest stem fresh weight similar to calcium peroxide (20 μM) and magnesium peroxide (10 μM). In addition, the use of vitamin K 3 resulted in the highest accumulation of chlorophyll (chla + chlb) in the leaves, an increase of nearly two-fold over the hypoxic control plants. Furthermore under hypoxia, calcium peroxide (20 μM) and mag-nesium peroxide (10 μM) produced the highest leaf biomass (FW) followed by vitamin K 3 . Vitamin K 3 (1 μM) also favored root growth in bean seedlings under hypoxia; it produced the largest in-crease in root length and root biomass (DW) similar to calcium peroxide and magnesium peroxide. Based on the overall shoot and root growth response of bean seedlings to various anti-hypoxic substances under hypoxic conditions, calcium peroxide, magnesium peroxide and vitamin K 3 per-formed better than hydrogen peroxide. These findings show that vitamin K 3 and peroxide salts are * Corresponding author. C. B. Rajashekar et al. 3397 effective in alleviating hypoxic stress in bean seedlings and also, further highlight their potential for dealing with hypoxia in wide ranging situations.
Organic material mulching has been used extensively to allow Phyllostachys praecox to promote growth and development of shoots. However, the bamboo forest always showed a significant degradation, probably due to anaerobic damage caused by the mulching after several years. Therefore, we have innovatively proposed an improvement measure to aerate the underground pipes for the first time. We investigated the role of subsurface pipe aeration in regulating root hypoxia to reduce the stress and to identify the degradation mechanism. Results showed that aeration increased oxygen concentration, shoot yield and root growth compared with mulching, and the aeration enhanced the concentration of indole-3-acetic acid (IAA) and the expression of Aux/IAAs ( Aux1 , Aux2 , Aux3 , and Aux4 ). Aeration reduced gibberellin (GA), ethylene (ETH), and abscisic acid (ABA) contents as well as anaerobic enzyme activities (alanine transaminase, AlaAT; alcohol dehydrogenase, ADH; pyruvate decarboxylase, PDC; and lactate dehydrogenase, LDH), which alleviated root damage in anoxic conditions. Furthermore, correlation showed that the activities of ADH, LDH, PDC, and AlaAT showed significant linear correlations with soil oxygen levels. RDA analyses showed that ABA, IAA, and ETH were found as the key driving hormones of Aux/IAAs in the root of the forest mulched with organic material. Here we show that subsurface aeration increases soil oxygen concentration, shoot yield, root growth and regulates phytohormone concentrations and Aux/IAAs expression, which reduces anaerobic enzyme activities. Consequently, subsurface pipe aeration is an effective measure to mitigate the degradation of bamboo forests caused by soil hypoxia that results from organic material mulching.
Pine bark is locally available in Zimbabwe and is widely in vegetable seedling production. However, it lacks essential nutrients for seedling growth. Goat manure was used to supplement nutrients when pine bark is used as growing media. The main object of the study was to determine the effect of pine bark amended with goat manure on tomato seedling emergence and seedling quality parameter which were stem diameter and stem length. The study was carried out at the Tobacco Research Board which is located 15 kilometers East of Harare at an altitude of latitude 17 0 55' S and longitude 31 0 08' E. The experiment was laid out in a 3 X 3 Factorial in a Completely Randomized Design with three replicates. The experiment had nine treatments with three different growing media which were un-amended pine bark, pine bark amended with goat manure and pine bark amended with Calcium carbonate (CaCO 3). It also had three fertilizer rates which were 0 ppm, 75 ppm and 150 ppm float fertilizer. Results from this study showed that the different media and fertilizer combinations had a significant effect (P<0.05) on seedling emergence, stem diameter and stem length. From the results pine bark amended with goat manure significantly increase seedling emergence, stem diameter and stem length compared to un-amended pine bark and pine bark amended with CaCO 3. A combination of pine bark amended with goat manure and 75 ppm float fertilizer had a significantly high emergence percentage, stem length and stem diameter compared to other media and fertilizer combinations. ii Dedication This project is dedicated to my parents Mr and Mrs Madziwa. iii
Plant-growth-promoting rhizobacteria (PGPR) have been shown to relieve various biotic and abiotic stresses, but little information is available regarding their influence on germination and seedling growth of aged seeds. We isolated a promising PGPR from rescuegrass (Bromus cartharticus Vahl) roots and investigated the effect of PGPR biopriming combined with another seed priming treatment on aged rescuegrass seeds using an orthogonal matrix design with four factors. A potential ageing-repair bacterium, BCR5 (Pseudomonas geniculata), was selected from the screening trials and was identified. The reintroduction of strain BCR5 into the aged seeds pre-primed with different approaches had positive effects on germination and seedling growth. The results indicated that the bacterial cell density was the most effective factor for seed germination and vigour. Four factors were optimized for this study, including an artificial ageing duration of 54.21 h, bacterial cell density of 527.50 × 10 ⁶ CFU·mL ⁻¹ , and priming with H 2 O 2 for 14.50 h, after analyzing the range and variance, and using binary quadratic regressions. Furthermore, the treatment also affected the content of malondialdehyde and the activities of superoxide dismutase and peroxidase. Bio-priming of the PGPR with another seed priming approach could be exploited as a promising technique for reinvigorating aged seeds. Moreover, we unexpectedly found that an appropriate artificial ageing treatment could break seed dormancy.
In order to study the priming of naturally aged seed with melatonin on seedling emergence and seedling growth of safflower under field condition, an experiment was conducted in 2017 at the Research Field of the college of Aburaihan, University of Tehran. The experimental design was factorial arrangement in randomized complete block design with four replicates. The treatments consists of seed quality (1-naturally aged seed 2- new seed) and seed priming (1-without priming 2- hydropriming 3- Melatonin 0.1 mM 4- Melatonin 0.5 mM). The results indicated that the highest amount of seed germination and rate in naturally aged seed obtained with seed priming by melatonin at 0.1 mM concentration and hydropriming. Also the highest amount of leaf area and biomass obtained with seed priming by melatonin at 0.1 mM concentration.Therefore, the characteristics of safflower seedling emergence and growth under field conditions can be improved by applying seed priming with Melatonin and Hydropriming.
In order to study the priming on storage capability of the primed seed of safflower, an experiment was conducted in 2017 at the seed technology laboratory of the college of Aburaihan, University of Tehran. The experimental design was a factorial arrangement in complete randomized design with four replicates. The treatments consist of seed quality (1-naturally aged seed 2- new seed) and seed priming (1-without priming 2- hydropriming 3- Melatonin 0.1 mM 4- Melatonin 0.5 mM) that post-priming storage for 7 months. The results indicated that the highest amount of seed germination obtained in control seed and there is no difference between priming levels. Also the highest amount of germination rate obtained by seed priming with melatonin in the naturally aged seed. The results showed that highest amount of dry matter and seedling length obtained with seed priming by melatonin. Therefore it seems that the characteristic of primed seed at storage time could retain by seed priming with melatonin.
Background:
In recognition of the 200th anniversary of Charles Darwin's birth, this short article on flooding stress acknowledges not only Darwin's great contribution to the concept of evolution but also to the study of plant physiology. In modern biology, Darwin-inspired reductionist physiology continues to shed light on mechanisms that confer competitive advantage in many varied and challenging environments, including those where flooding is prevalent.
Scope:
Mild flooding is experienced by most land plants but as its severity increases, fewer species are able to grow and survive. At the extreme, a highly exclusive aquatic lifestyle appears to have evolved numerous times over the past 120 million years. Although only 1-2% of angiosperms are aquatics, some of their adaptive characteristics are also seen in those adopting an amphibious lifestyle where flooding is less frequent. Lowland rice, the staple cereal for much of tropical Asia falls into this category. But, even amongst dry-land dwellers, or certain of their sub-populations, modest tolerance to occasional flooding is to be found, for example in wheat. The collection of papers summarized in this article describes advances to the understanding of mechanisms that explain flooding tolerance in aquatic, amphibious and dry-land plants. Work to develop more tolerant crops or manage flood-prone environments more effectively is also included. The experimental approaches range from molecular analyses, through biochemistry and metabolomics to whole-plant physiology, plant breeding and ecology.
Corn (Zea mays L.) root adaptation to pH 3.5 in comparison with pH 6. 0 (control) was investigated in long-term nutrient solution experiments. When pH was gradually reduced, comparable root growth was observed irrespective of whether the pH was 3.5 or 6.0. After low-pH adaptation, H+ release of corn roots in vivo at pH 5.6 was about 3 times higher than that of control. Plasmalemma of corn roots was isolated for investigation in vitro. At optimum assay pH, in comparison with control, the following increases of the various parameters were caused by low-pH treatment: (a) hydrolytic ATPase activity, (b) maximum initial velocity and Michaelis constant (c) activation energy of H+-ATPase, (d) H+-pumping activity, (e) H+ permeability of plasmalemma, and (f) pH gradient across the membranes of plasmalemma vesicles. In addition, vanadate sensitivity remained unchanged. It is concluded that plasmalemma H+-ATPase contributes significantly to the adaptation of corn roots to low pH. A restricted net H+ release at low pH in vivo may be attributed to the steeper pH gradient and enhanced H+ permeability of plasmalemma but not to deactivation of H+-ATPase. Possible mechanisms responsible for adaptation of plasmalemma H+-ATPase to low solution pH during plant cultivation are discussed.
Plants, like animals, are obligate aerobes, but due to their inability to move, have evolved adaptation mechanisms that enable them to survive short periods of low oxygen supply, such as those occurring after heavy rain or flooding. Crop plants are often grown on soils subject to waterlogging and many are sensitive to waterlogging of the root zone. The combination of unfavourable weather conditions and suboptimal soil and irrigation techniques can result in severe yield losses. The molecular basis of the adaptation to transient low oxygen conditions has not been completely characterized, but progress has been made towards identifying genes and gene products induced during low oxygen conditions. Promoter elements and transcription factors involved in the regulation of anaerobically induced genes have been characterized. In this paper an account is presented of the molecular strategies that have been used in an attempt to increase flooding tolerance of crop plants.
Flooding of soils results in acute oxygen deprivation (anoxia) of plant roots during winter in temperate latitudes, or after irrigation, and is a major problem for agriculture. One early response of plants to anoxia and other environmental stresses is downregulation of water uptake due to inhibition of the water permeability (hydraulic conductivity) of roots (Lp(r)). Root water uptake is mediated largely by water channel proteins (aquaporins) of the plasma membrane intrinsic protein (PIP) subgroup. These aquaporins may mediate stress-induced inhibition of Lp(r) but the mechanisms involved are unknown. Here we delineate the whole-root and cell bases for inhibition of water uptake by anoxia and link them to cytosol acidosis. We also uncover a molecular mechanism for aquaporin gating by cytosolic pH. Because it is conserved in all PIPs, this mechanism provides a basis for explaining the inhibition of Lp(r) by anoxia and possibly other stresses. More generally, our work opens new routes to explore pH-dependent cell signalling processes leading to regulation of water transport in plant tissues or in animal epithelia.
Keilin's classic paper of 1925 [Keilin (1925) Proc. R. Soc. London Ser. B 100, 129-151], achieved with simple, but elegant, techniques, describes the cytochrome components of the respiratory chain and their roles in intracellular respiration and oxygen consumption. Since that time, a tremendous amount of work has clarified the intricate details of the prosthetic groups, cofactors and proteins that comprise the respiratory chain and associated machinery for ATP synthesis. The work has culminated in advanced crystallographic and spectroscopic methods that provide structural and mechanistic details of this mitochondrial molecular machinery, in many instances to atomic level. I review here the current state of understanding of the mitochondrial respiratory chain in terms of structures and dynamics of the component proteins and their roles in the biological electron and proton transfer processes that result in ATP synthesis. These advances, together with emerging evidence of further diverse roles of mitochondria in health and disease, have prompted a new era of interest in mitochondrial function.
Considering the ability of food processing companies to consistently manu facture safe foods with uniform quality over the past 20 or 30 years without these new tools and new systems, one might expect that quality control improvements would be marginal. On the other hand, these changes have already provided sub stantial opportunities for process and product improvement. This second edition is intended to update the basic concepts and discuss some of the new ones. Preface to the First Edition If an automobile tire leaks or an electric light switch fails, if we are short-changed at a department store or erroneously billed for phone calls not made, if a plane de parture is delayed due to a mechanical failure-these are rather ordinary annoy ances which we have come to accept as normal occurrences. Contrast this with failure of a food product. If foreign matter is found in a food, if a product is discolored or crushed, if illness or discomfort occurs when a food product is eaten-the consumer reacts with anger, fear, and sometimes mass hys teria. The offending product is often returned to the seller, or a disgruntled letter is written to the manufacturer. In an extreme case, an expensive law suit may be filed against the company. The reaction is almost as severe if the failure is a dif ficult-to-open package or a leaking container. There is no tolerance for failure of food products.
Plants, like animals, are obligate aerobes, but due to their inability to move, have evolved adaptation mechanisms that enable
them to survive short periods of low oxygen supply, such as those occurring after heavy rain or flooding. Crop plants are
often grown on soils subject to waterlogging and many are sensitive to waterlogging of the root zone. The combination of unfavourable
weather conditions and suboptimal soil and irrigation techniques can result in severe yield losses. The molecular basis of
the adaptation to transient low oxygen conditions has not been completely characterized, but progress has been made towards
identifying genes and gene products induced during low oxygen conditions. Promoter elements and transcription factors involved
in the regulation of anaerobically induced genes have been characterized. In this paper an account is presented of the molecular
strategies that have been used in an attempt to increase flooding tolerance of crop plants.
Corn (Zea mays L.) root adaptation to pH 3.5 in comparison with pH 6.0 (control) was investigated in long-term nutrient solution experiments. When pH was gradually reduced, comparable root growth was observed irrespective of whether the pH was 3.5 or 6.0. After low-pH adaptation, H⁺ release of corn roots in vivo at pH 5.6 was about 3 times higher than that of control. Plasmalemma of corn roots was isolated for investigation in vitro. At optimum assay pH, in comparison with control, the following increases of the various parameters were caused by low-pH treatment: (a) hydrolytic ATPase activity, (b) maximum initial velocity and Michaelis constant (c) activation energy of H⁺-ATPase, (d) H⁺-pumping activity, (e) H⁺ permeability of plasmalemma, and (f) pH gradient across the membranes of plasmalemma vesicles. In addition, vanadate sensitivity remained unchanged. It is concluded that plasmalemma H⁺-ATPase contributes significantly to the adaptation of corn roots to low pH. A restricted net H⁺release at low pH in vivo may be attributed to the steeper pH gradient and enhanced H⁺ permeability of plasmalemma but not to deactivation of H⁺-ATPase. Possible mechanisms responsible for adaptation of plasmalemma H⁺-ATPase to low solution pH during plant cultivation are discussed.
In 0.1 mol/l KH2PO4–NaOH buffer solution (pH 7.0), the multi-walled carbon nanotubes (MWNTs) modified electrode exhibits high stability and strong catalytic effect toward the electrochemical oxidation of nitric oxide (NO). Upon further modification with a thin film of nafion which is capable of preventing interference from anions, especially nitrite, this modified electrode can be employed as a NO sensor in solution with fast response and high selectivity. The experimental conditions, such as supporting electrolyte and amounts of nafion, as well as scan rate have been optimized. The currents (measured by constant potential amperometry) increase linearly with the concentrations of NO in the range of 2×10−7–1.5×10−4mol/l. The calculated detection limit is 8.0×10−8mol/l. Moreover, the determination is free from the interference of nitrite and some biological substances. The experimental results show that NO might be adsorbed on the surface of electrode and then transfer electrons.
These proceedings contain 5 parts, which include several chapters each, discussing: seed development; seed germination and dormancy; desiccation and other stress tolerance, and conservation; seed ecology; and seed biotechnology.
For studies of the effects of seedbed properties on crop emergence, experiments were carried out in shallow plastic boxes. In some experiments, it was examined whether rainfall after sowing could cause oxygen deficiency in the seedbed sufficiently severe to hamper emergence. Crops studied were barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), oilseed rape (Brassica napus var. oleifera, L., Metzg.) and pea (Pisum sativum L.). For harmful oxygen deficiency to develop it appeared that rainfall would need to cause structural collapse of the surface layer followed by continuously wet weather accompanied by slow drainage and high oxygen consumption in the soil; in the experiments the latter was achieved by large amounts of easily decomposable organic matter. It was concluded that such conditions are rare in the field. Therefore, unless rainfall after sowing generates surface water for an extended period, the poor crop emergence often observed after such rainfall is nearly always caused not by oxygen deficiency, but by surface layer hardening when this layer dries.
The involvement of the seed coat in low-temperature germination of melon seeds was examined in two accessions differing in their ability to germinate at 14°C: Noy Yizre'el (a cold-sensitive cultivar) and Persia 202 (a cold-tolerant breeding line). Decoating resulted in full germination of Noy Yizre'el at 14°C, but splitting the coat increased germination only partially. Thus, the inhibition of Noy Yizre'el germination at 14°C is not due to physical constraint on radicle protrusion. At 25°C, seeds of both accessions submerged in water or agar germinated fully as long as the hilum aperture remained uncovered. Submerging the whole seed, or covering the hilum with lanolin, strongly depressed germination of Noy Yizre'el but not of Persia 202. Accessions differed in germination response to decreasing O2 concentration, with Noy Yizre'el showing higher sensitivity to hypoxia. These differences were correlated with differences in seed coat structure as well as in embryo sensitivity to hypoxia. Intercellular spaces in the outer layer of the seed coat were evident in the more tolerant Persia 202, while in the sensitive Noy Yizre'el this layer was completely sealed. Sensitivity to hypoxia increased at 15°C as compared with 25°C, the increase being greater in Noy Yizre'el. It is proposed that the seed coat-imposed dormancy at low temperature in Noy Yizre'el is the combined result of more restricted oxygen diffusion through the seed coat and a greater embryo sensitivity to hypoxia, rather than to physical constraints of radicle break-through or impairment of imbibition.
Background and aims
Phosphorus (P) nutrition is very important during early maize seedling growth. Remobilization of endogenous seed P and uptake of exogenous P are therefore of prime importance during this period. Our objectives were to study the effect of the availability of endogenous and exogenous P on i) remobilization of endogenous seed P, ii) the beginning of exogenous P uptake and its intensity, iii) their interaction and effect on seedling development.
Methods
Seeds with high and low reserves of endogenous seed P were cultivated at three rates of availability of exogenous P (0, 100, 1,000 μM) over a growth period of 530 cumulated degree days after sowing. Exogenous P was labeled with radioactive P (32P) to distinguish the two fluxes of P in seedlings, one due to remobilization of seed P and the other to uptake of exogenous P.
Results
Initially, 86% of endogenous seed P was localized in the scutellum, mainly in the form of phytate, regardless of initial endogenous seed P. At 89 cumulated degree days after sowing (base temperature: 10°C), 98% of seed phytate was hydrolyzed in all treatments. In treatments with available exogenous P, significant uptake of exogenous P started at 71 cumulated degree days after sowing. Efficient uptake of exogenous P depended on its availability, but was independent of phytate hydrolysis and seedling P status. Significant loss of P from germinating seeds due to efflux was observed and was also independent of the availability of exogenous P.
Conclusions
Our results show that hydrolysis of seed P was not influenced by the availability of exogenous P, and conversely, that uptake of exogenous P was not influenced by endogenous P in the seed. This suggests that remobilization of endogenous seed P and uptake of exogenous P by seedling roots are controlled independently.
Some microorganisms can prevent seed germination and retard the extension growth of seedlings roots by providing a sink for available oxygen and by producing phytotoxic metabolites. These effects have been alleviated in the laboratory by dressing cereal seed with a formulation containing calcium peroxide and lime.
In this study, antioxidant activities of water-soluble protein extracts from chickpeas and white beans were investigated. The area under the curve (AUC) values of lyophilized crude protein extracts (dialyzed or undialyzed) from thermally processed (121 °C for 20 min) or heat-treated (90 °C for 20 min) chickpeas (73–91 μmol trolox/g) and white beans (39–67 μmol trolox/g) indicated a higher free radical-scavenging capacity and thermostability for chickpea proteins than for white bean proteins. The thermal processing also increased the Fe+2-chelating capacity of lyophilized chickpea crude protein extracts 1.8-fold whereas it caused a 2.3-fold reduction in the Fe+2-chelating capacity of lyophilized white bean crude protein extracts. Dialysis increased the protein content of lyophilized chickpea extracts 1.5–2-fold but it did not affect the protein content of lyophilized white bean extracts significantly. Ammonium sulfate precipitation was not effective for selective precipitation of antioxidant proteins. However, it improved the free radical-scavenging capacity of lyophilized protein extracts from thermally processed chickpeas and white beans by almost 25% and 100%, respectively. DEAE-cellulose chromatography, indicated the presence of five (A1–A5) and three (B1–B3) antioxidant protein fractions in heat-treated and thermally processed chickpea protein extracts, respectively, and can be used for the partial purification of antioxidant proteins. The results of this study showed the good potential of chickpea proteins as thermostable natural food antioxidants.
Seeds of most crops can be severely damaged and lose vigor when stored under conditions of high humidity and temperature. The aged seeds are characterized by delayed germination and slow post-germination growth. To date, little is known about the physiological mechanisms responsible for slow root growth of seedlings derived from aged seeds. Plasma membrane H+-ATPase is a universal H+ pump in plant cells and is involved in various physiological processes including the elongation growth of plant cells. In the present study, we investigated the effect of a mild seed ageing treatment on plasma membrane H+-ATPase activity of seedling roots. Maize (Zea mays L.) seeds with 17% water content were aged at 45 °C for 30 h. The aged seeds showed a 20% reduction in germination. Seedlings from aged seeds grew slowly during an experimental period of 120 h after imbibition. Plasma membranes of maize seedling roots were isolated for investigation in vitro. Plasma membrane H+-ATPase (EC 3.6.3.6) activity was 14% lower for seedling roots developed from aged seeds as compared to control seeds. Protein gel immunoblotting analysis demonstrated that the reduced activity of plasma membrane H+-ATPase was attributed to a decrease in steady-state protein concentration of this enzyme. In conclusion, seed ageing causes a lower steady-state enzyme concentration of the H+-ATPase in the plasma membrane, which is related to slow germination and post-germination growth of seedling roots.
Some recent modifications of the protein assay by the method of Lowry, Rosebrough, Farr, and Randall (1951, J. Biol. Chem.193, 265–275) have been reexamined and altered to provide a consolidated method which is simple, rapid, objective, and more generally applicable. A DOC-TCA protein precipitation technique provides for rapid quantitative recovery of soluble and membrane proteins from interfering substances even in very dilute solutions (< 1 μg/ml of protein). SDS is added to alleviate possible nonionic and cationic detergent and lipid interferences, and to provide mild conditions for rapid denaturation of membrane and proteolipid proteins. A simple method based on a linear log-log protein standard curve is presented to permit rapid and totally objective protein analysis using small programmable calculators. The new modification compared favorably with the original method of Lowry et al.
Anaerobiosis rapidly induces alcohol dehydrogenase (ADH), an enzyme of the fermentation pathway, in different parts of rice seedlings. After initiation of anaerobiosis, the activity of the enzyme increases linearly for 3 days or more. The ADH activity is anaerobically inducible even in mature rice leaves in contrast to maize which shows no induction in mature leaves. Rice ADH activity can also be induced by an auxin analog, 2,4-dichlorophenoxyacetic acid, under aerobic conditions. The experimental results show that anaerobiosis increases the ADH mRNA level, indicating that the ADH enzyme is regulated at the transcriptional level. Starch gel electrophoresis of a protein extract from rice shows 3 distinct forms of ADH. The amounts of the 3 forms vary with the organ, suggesting that the expression of ADH genes is organ-specific. Sequencing data show that the two different cloned cDNA copies of ADH mRNAs are derived from two different genes.
Nonsymbiotic hemoglobins are broadly present across the plant kingdom; however, the function of these proteins is unknown. Cultured maize cells have been transformed to constitutively express a barley hemoglobin gene in either the sense (HB+) or antisense (HB-) orientation. Hemoglobin protein in the transformed cell lines correspondingly was higher or lower than in wild-type cells under normal atmospheric conditions. Limiting oxygen availability, by placing the cells in a nitrogen atmosphere for 12 hr, had little effect on the energy status of cells constitutively expressing hemoglobin, but had a pronounced effect on both wild-type and HB- cells, where ATP levels declined by 27% and 61%, respectively. Total adenylates in these cells were approximately 35% lower than in HB+ cells. Energy charge was relatively unaffected by the treatment in HB+ and wild-type cells, but was reduced from 0.91 to 0.73 in HB- cells, suggesting that the latter were incapable of maintaining their energy status under the low oxygen regime. Treatment of the cells grown in an air atmosphere with antimycin A gave essentially the same results. It is suggested that nonsymbiotic hemoglobins act in plants to maintain the energy status of cells in low oxygen environments and that they accomplish this effect by promoting glycolytic flux through NADH oxidation, resulting in increased substrate-level phosphorylation. Hypoxic acclimation of plants is an example of this effect in nature. Nonsymbiotic hemoglobins are likely ancestors of an early form of hemoglobin that sequestered oxygen in low oxygen environments, providing a source of oxygen to oxidize NADH to provide ATP for cell growth and development.
Biological systems have very different internal ion compositions in comparison with their surrounding media. The difference is maintained by transport mechanisms across the plasma membrane and by internal stores. On the plasma membrane, we can classify these mechanisms into three types, pumps, porters, and channels. Channels have been extensively studied, particularly since the advent of the patch clamp technique, which opened new windows into ion channel selectivity and dynamics. Pumps, particularly the plasma membrane Ca(2+)-ATPase, and porters are more illusive. The technique described in this paper, the self-referencing, ion-selective (or Seris) probe, has the ability to monitor the behavior of membrane transport mechanisms, such as the pumps and porters, in near to real-time by non-invasively measuring local extracellular ion gradients with high sensitivity and square micron spatial resolution. The principles behind the self-referencing technique are described with an overview of systems utilizing ion, electrochemical and voltage sensors. Each of these sensors employs the simple expedient of increasing the system resolution by self-referencing and, thereby, removing the drift component inherent to all electrodes. The approach is described in detail, as is the manner in which differential voltage measurements can be converted into a flux value. For the calcium selective probes, we can resolve flux values in the low to sub pmol.cm(-2)s(-1) range. Complications in the use of the liquid ion exchange cocktail are discussed. Applications of the calcium selective probe are given, drawing on examples from the plant sciences, developmental biology, muscle physiology, and the neurosciences.
Plants lack specialised organs and circulatory systems, and oxygen can fall to low concentrations in metabolically active, dense or bulky tissues. In animals that tolerate hypoxia or anoxia, low oxygen triggers an adaptive inhibition of respiration and metabolic activity. Growing potato tubers were used to investigate whether an analogous response exists in plants. Oxygen concentrations fall below 5% in the centre of growing potato tubers. This is accompanied by a decrease of the adenylate energy status, and alterations of metabolites that are indicative of a decreased rate of glycolysis. The response to low oxygen was investigated in more detail by incubating tissue discs from growing tubers for 2 hours at a range of oxygen concentrations. When oxygen was decreased in the range between 21% and 4% there was a partial inhibition of sucrose breakdown, glycolysis and respiration. The energy status of the adenine, guanine and uridine nucleotides decreased, but pyrophosphate levels remained high. The inhibition of sucrose breakdown and glycolysis was accompanied by a small increase of sucrose, fructose, glycerate-3-phosphate, phosphenolpyruvate, and pyruvate, a decrease of the acetyl-coenzymeA:coenzymeA ratio, and a small increase of isocitrate and 2-oxoglutarate. These results indicate that carbon fluxes are inhibited at several sites, but the primary site of action of low oxygen is probably in mitochondrial electron transport. Decreasing the oxygen concentration from 21% to 4% also resulted in a partial inhibition of sucrose uptake, a strong inhibition of amino acid synthesis, a decrease of the levels of cofactors including the adenine, guanine and uridine nucleotides and coenzymeA, and attenuated the wounding-induced increase of respiration and invertase and phenylalanine lyase activity in tissue discs. Starch synthesis was maintained at high rates in low oxygen. Anoxia led to a diametrically opposed response, in which glycolysis rose 2-fold to support fermentation, starch synthesis was strongly inhibited, and the level of lactate and the lactate:pyruvate ratio and the triose-phosphate:glycerate-3-phosphate ratio increased dramatically. It is concluded that low oxygen triggers (i) a partial inhibition of respiration leading to a decrease of the cellular energy status and (ii) a parallel inhibition of a wide range of energy-consuming metabolic processes. These results have general implications for understanding the regulation of glycolysis, starch synthesis and other biosynthetic pathways in plants, and reveal a potential role for pyrophosphate in conserving energy and decreasing oxygen consumption.
Attempts were made to promote germination of naturally and artificially aged rice seeds by treating them with cerium nitrate. The germination rate, germination index, and vigor index of aged rice seed were significantly increased by cerium. It was because the treatments of aged rice seed with cerium nitrate enhanced respiratory rate and activities of superoxide dismutase, catalase, and peroxidase, and decreased superoxide O2- and malondialdehyde contents that plasma membrane permeability was reduced. It was suggested that cerium be used for the seed treatment before sowing.
Flooding reduces the ability of roots to absorb water. The molecular basis for this paradox involves the regulation of water-channel proteins by the pH inside root cells.
The mechanisms of plant membrane water permeability have remained elusive until the recent discovery in both vacuolar and plasma membranes of a class of water channel proteins named aquaporins. Similar to their animal counterparts, plant aquaporins have six membrane-spanning domains and belong to the MIP superfamily of transmembrane channel proteins. Their very high efficiency and selectivity in transporting water molecules have been mostly characterized using heterologous expression in Xenopus oocytes. However, techniques set up to measure the osmotic water permeability of plant membranes such as transcellular osmosis, pressure probe measurements, or stopped-flow spectrophotometry are now being used to analyze the function of plant aquaporins in their native membranes. Multiple mechanisms, at the transcriptional and posttranslational levels, control the expression and activity of the numerous aquaporin isoforms found in plants. These studies suggest a general role for aquaporins in regulating transmembrane water transport during the growth, development, and stress responses of plants. Future research will investigate the integrated function of aquaporins in long-distance water transport and cellular osmoregulation.
Oxygen deficiency in the rooting zone occurs with poor drainage after rain or irrigation, causing depressed growth and yield of dryland species, in contrast with native wetland vegetation that tolerates such conditions. This review examines how roots are injured by O2 deficiency and how metabolism changes during acclimation to low concentrations of O2. In the root apical meristem, cell survival is important for the future development; metabolic changes under anoxia help maintain cell survival by generating ATP anaerobically and minimizing the cytoplasmic acidosis associated with cell death. Behind the apex, where cells are fully expanded, ethylene-dependent death and lysis occurs under hypoxia to form continuous, gas-filled channels (aerenchyma) conveying O2 from the leaves. This selective sacrifice of cells may resemble programmed cell death and is distinct from cell death caused by anoxia. Evidence concerning alternative possible mechanisms of anoxia tolerance and avoidance is presented.
Calcium is an important factor in the ability of plants to resist salt stress, possibly because of its role in maintaining membrane integrity. We studied the effects of NaCl stress on membrane-associated Ca in corn root protoplasts (Zea mays L. cv Pioneer 3377) using the fluorescent Ca probe chlorotetracycline (CTC). Protoplasts were isolated from the cortex of primary roots of corn seedlings (Gronwald and Leonard, Plant Physiol 1982 70: 1391-1395). After a 30 minute incubation in 50 micromolar CTC, the protoplasts were exposed to isosmotic treatment solutions containing various concentrations of NaCl just before fluorimetric analysis. Increasing NaCl concentrations caused a progressive reduction in net CTC fluorescence, to 50% of control values at 150 mm NaCl. NaCl did not displace CTC from the cells, nor did it directly interfere with Ca-CTC binding. Tests with CsCl, RbCl, KCl, LiCl, Na(2)SO(4), NaNO(3), and NaBr indicated that the reduction in CTC fluorescence was not specific to either Na or Cl, but may have been due to increased ionic strength of the treatment solutions. Like CTC fluorescence, root growth of intact corn seedlings was not specifically sensitive to Na, but was inhibited by several monovalent cations in the order Li > Cs > Rb > Na > K. CTC fluorescence at 100 mm NaCl was restored to unstressed levels by increasing Ca concentrations. Since our salt treatments were isosmotic, we conclude that the ionic component of salt stress displaces Ca from membranes of corn root cells.
Spectrophotometry and spectrofluorometry
- D A Harris
Harris, D.A. 1987. Spectrophotometric assays,
p. 59-60. In: Harris, D.A. and C.L. Bashford
(eds.). Spectrophotometry and spectrofluorometry. I.R.L. Press, Oxford, UK.