Solution Culture Experiments Research Articles

Immobilization of Heavy Metals by Phosphorus-solubilizing Bacteria and Inhibition of Cd and Pb Uptake by Wheat

Phosphorus-solubilizing microorganisms convert insoluble phosphorus in the soil into phosphorus that can be absorbed by plants. Soluble phosphate combines with heavy metals to form precipitation, reducing the content of available heavy metals, thereby reducing the absorption of heavy metals by crops, which plays an important role in the remediation of heavy metal-contaminated soil. The effects of the immobilization of Cd and Pb and the release of PO43- by the phosphorus-solubilizing bacterium Klebsiella sp. M2 were studied through solution culture experiments. In addition, the effects of strain M2 on wheat uptake of Cd and Pb and its microbiological mechanism were also explored through pot experiments. The results showed that strain M2 reduced the concentrations of Cd and Pb and increased the concentration of PO43- in the solution through cell wall adsorption and induced phosphate precipitation. Pot experiments showed that compared to those in the CK group and inactivated strain M2 group, inoculation with live strain M2 significantly increased （123%-293%） the contents of Ca2-P and Ca8-P in rhizosphere soil, decreased the content of DTPA-Cd （34.48%） and DTPA-Pb （36.72%） in wheat rhizosphere soil, and thus hindered the accumulation of Cd and Pb in wheat grains. Moreover, high-throughput sequencing results showed that strain M2 significantly increased the diversity of wheat rhizosphere bacterial communities； increased the relative abundance of Proteobacteria, Gemmatimonadetes, and Bacteroidota in wheat rhizosphere soil； and increased the proportion of heavy metal-immobilizing and phosphorus-promoting bacteria in wheat rhizosphere soil （mainly Sphingomonas, Nocardioides, Bacillus, Gemmatimonas, and Enterobacter）. These bacterial genera played an important role in immobilizing heavy metals and preventing wheat from absorbing heavy metals. These results provide bacterial resources and theoretical basis for the bioremediation of heavy metal-contaminated farmland.

Effects of Lead Pollution on Photosynthetic Characteristics and Chlorophyll Fluorescence Parameters of Different Populations of Miscanthus floridulus

This study was conducted in order to study the effect of different concentrations of lead pollution on the photosynthetic characteristics and growth of Miscanthus floridulus, and to reveal its photosynthetic adaptability to lead stress. The differences of gas exchange parameters, chlorophyll fluorescence characteristics and photosynthetic pigment of two Miscanthus floridulus populations, one population from Boluo an uncontaminated site, and another population from Dabaoshan, a mine site, were compared and studied through nutrient solution culture experiments treated with heavy metal lead (Pb) in green house. The results showed that (1) under Pb stress, the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci), and chlorophyll content (Chl) of the leaves of the two populations decreased in different amplitude. Under moderate and severe Pb stress (80 mg·L−1, 120 mg·L−1, 240 mg·L−1), the plant biomass of non-mining population and mining population plants were 54.5%, 39.7%, 29.4% and 70.4%, 54.7%, 50.9% of the control, respectively. (2) Stomatal restriction was the main factor for the Pn’s decrease in the leaves of the non-mine population under light Pb stress, while the non-stomatal restriction was the main factor for Pn’s decrease in the leaves of the non-mine population under middle and high Pb stresses. (3) Under Pb stress, the maximum photochemical efficiency (Fv/Fm) and potential activity (Fv/Fo) of PS II reaction centers in the two populations of M. floridulus decreased. However, Fv/Fm and Fv/Fo showed a smaller decrease, but the capability to utilize light and the potential to activate PSII of the mine population remained higher than that of the non-mine population. The changes of photochemical quenching coefficient (qP) and non-photochemical quenching coefficient (NPQ) of PSⅡ showed that qP value decreased and NPQ value increased in the two populations under Pb stress. On the whole, the resistance mining area population had a low qP reduction and a large increase in NPQ. Electronic transfer rate (ETR) and PSII actual fluorescence efficiency (ΦPSII) of the mine population changed slightly under Pb stress. These results indicated that when under Pb stress, the electron transport activity and photosynthetic apparatus were damaged less in the mine population with high resistance than in the non-mine population with low resistance. Conclusion: the mining population of M. floridulus has strong tolerance to Pb, which is suitable for the pioneer species of gramineae in vegetation restoration construction in metal mining area.

Poly-γ-glutamic acid-producing bacteria reduce wheat Cd uptake by promoting Cd transfer from macro-to micro-aggregates in Cd-contaminated soil

Heavy metal immobilization using poly-γ-glutamic acid-producing bacteria is a novel and environmentally friendly technique for the remediation of heavy metal-contaminated soil. However, only a few studies have investigated the effects of γ-PGA-producing bacteria on the Cd uptake of wheat plants and the Cd distribution in soil aggregates in Cd-polluted soils. In this study, solution culture and pot experiments were used to investigate the Cd immobilization effect and mechanism of the γ-PGA-producing bacteria Bacillus subtilis W7 and Bacillus amyloliquefaciens W25. In the two bacteria-inoculated culture media, the concentration of Cd decreased, whereas the pH, cell growth, γ-PGA production and cell-immobilized Cd significantly increased over time. Strain W25 exhibited a higher ability to produce γ-PGA and immobilize Cd than strain W7. In the pot experiments, the grain Cd content of wheat was reduced by 24–35% and the DTPA-Cd content was decreased by 22–37% in the rhizosphere soils inoculated with both strains compared to the control. Furthermore, strain W25 had a greater ability to decrease the grain Cd uptake than strain W7. Inoculation with the two strains significantly increased the pH, organic matter content, and urease activity and promoted the migration of Cd from large fractions (>0.25 mm) to small fractions (<0.048 mm) and the transformation of available Cd to unavailable Cd in wheat rhizosphere soil. Our results highlight the potential of γ-PGA-producing bacteria in remediating Cd-polluted soils for safe wheat producing.

Co-Application of Silicate and Low-Arsenic-Accumulating Rice Cultivars Efficiently Reduces Human Exposure to Arsenic-A Case Study from West Bengal, India.

We investigated the effect of practically realizable doses of silicate on arsenic (As) uptake by differential-As-accumulating rice cultivars grown on geogenically As-polluted soil. The possible health risk from the dietary ingestion of As through rice was also assessed. In addition, a solution culture experiment was conducted to examine the role of root-secreted weak acids in differential As acquisition by rice cultivars. When grown without silicate, Badshabhog accumulated a much smaller amount of As in grain (0.11 mg kg-1) when compared to the other three varieties. Satabdi, IR-36, and Khitish accumulated As in grain beyond the permissible limit (0.2 mg kg-1) for human consumption. The application of silicate effectively reduced the As content in the grain, husk, and straw of all of the cultivars. The grain As content fell to 17.2 and 27.6% with the addition of sodium metasilicate at the rates of 250 and 500 mg kg-1, respectively. In the case of Khitish, the grain As content was brought down within permissible limits by the applied silicate (500 mg kg-1). The integrated use of low-As-accumulating cultivars and silicate has great potential to reduce the public health risks associated with As. A positive correlation between root-secreted total weak acid and grain As content could explain the different rice cultivars' differential As acquisition capacity.

Sulfur Nutrition Affects Garlic Bulb Yield and Allicin Concentration.

Improving bulb yield and allicin content of garlic is important in meeting fresh and pharmaceutical market demands. Garlic plants have a high demand for sulfur (S) since allicin contains S atoms. Two experiments were conducted to identify the effect of S application rate on garlic yield and quality. In a field trial assessing six S application rates (0–150 kg S ha−1), cultivar ‘Glenlarge’ produced the greatest bulb weight (~90 g) and allicin content (521 mg bulb−1) with the application of 75 kg S ha−1. In contrast, cultivar ‘Southern Glen’ showed no response in bulb weight or allicin. This was likely due to high soil background S concentrations masking treatment effects. Subsequently, a solution culture experiment with cv. ‘Glenlarge’ evaluated six S application rates (188 to 1504 mg S plant−1, nominally equivalent to 25–200 kg S ha−1). In solution culture, bulb weight and allicin concentration increased with S rate. Highest bulb weight (~53 g bulb−1) and allicin concentration (~11 mg g−1 DW) were recorded at an S application of 1504 mg S plant−1. This is the first report to conclusively demonstrate the effect of S on yield and allicin in garlic grown in solution culture.

Free amino acids, carbon and nitrogen isotopic compositions responses to cadmium stress in two castor (Ricinus communis L.) species

Cadmium (Cd) toxicity induce various disturbances in metabolic processes and impair plant establishment. The composition of carbon and nitrogen stable isotopes (δ13C and δ15N) and free amino acids (FAAs) can reflect the response of plants to environmental stress. In the present study, a solution culture experiment was carried out, and the secretion characteristics of FAAs as well as δ13C and δ15N were evaluated as indicative of the functional performance of two castor species (Zibo-3 and Zibo-9) under various Cd concentrations stress (0, 1, 2, and 5 mg L−1). The results indicated that: 1) The treatment of the plants with 5 mg L−1 of a Cd solution resulted in a significant decline of biomasses by 22.4% and 11.6% in Zibo-3 and Zibo-9, respectively, relative to controls; additionally, the accumulation levels for Cd in Zibo-9 were higher than those in Zibo-3, thus Zibo-9 showed higher tolerance and enrichment ability to Cd. 2) The exposure of castor to Cd treatments results in significant modifications in individual FAAs, suggesting a differential sensitivity of each biosynthetic pathway to this stress; however, a positive correlation was found between the accumulation of total FAAs and Cd treatment dosages; higher proportion of asparagine and glutamate in total amino acids for Zibo-9, and abundant secretion of arginine in Cd treated Zibo-9 may be associated with the higher Cd-tolerance and Cd-accumulation in Zibo-9. 3) Cd stress increased leaf δ13C and δ15N values regardless of the castor species; δ13C and δ15N could be used as monitoring tools for heavy metal stress in plants.

Baseline hydroponic study for biofortification of bread wheat genotypes with iron and zinc under salinity: growth, ionic, physiological and biochemical adjustments

Salinity is one of the major abiotic stresses that is deteriorating soil fertility and reducing essential nutrients acquisition by plants around the world. Among staple food, wheat can be a primary source of micronutrients like Fe and Zn. The saline/saline-sodic and calcareous soils are deficient in Fe and Zn. In these regards, the aim of present study was to screen out wheat genotypes which can efficiently utilize Fe and Zn in saline conditions. Therefore, ten wheat genotypes (i.e., Ujala-2016, Punjab-2011, Galaxy-2013, Faisalabad-2008, Anaj-2017, SARC-I, SARC-VIII, Lasani-2008, Sehar-2006 and Inqalab-91) were exposed to varying rates of Zn (0.2, 0.4 µM) and Fe (25, 50 µM) under saline and normal conditions in a solution culture experiment. Salinity was developed by using NaCl salt, while the sources of Zn and Fe were ZnSO4.7H2O and FeSO4.7H2O, respectively. The data of various wheat growth and ionic parameters including root/shoot dry weight, chlorophyll contents, Zn, Fe, K and Na concentration in root and shoot of wheat genotypes were recorded using standard procedures. The results showed that Fe and Zn application significantly (p ≤ 0.05) increased wheat plant growth under salt stress. Among tested genotypes, Faisalabad-2008 and Galaxy-2013 performed better under saline conditions with maximum biomass production, Zn, Fe and K absorption. Thus, these both genotypes were found to be good source for future wheat breeding programs or can be grown by farmers owing to efficient Fe and Zn utilization as a gateway toward the production of Fe and Zn biofortified wheat under saline conditions.

Nitrogen limits zinc‐mediated stimulation of tillering in rice by modifying phytohormone balance under low‐temperature stress

AbstractZinc (Zn) can improve resistance of rice plants to abiotic stress and promote the recovery of rice tillers by influencing auxin (IAA) synthesis, Zn absorption is closely related to nitrogen (N) concentrations; however, the mechanisms by which Zn regulates rice tiller recovery at low temperatures under different N levels are rarely studied. In this study, a solution culture experiment was conducted at two temperatures, three different Zn concentrations, and two N concentrations. Low temperature during the vegetative stage damaged the rice antioxidant system, suppressed nutrient uptake, and decreased the number of tillers. Increasing Zn application improved the resistance of rice plants to low‐temperature stress under normal N levels, enhanced nutrient absorption, improved tiller bud cytokinin (CTK) concentrations, and the CTK/IAA ratio, which accelerated tiller recovery relative to plants receiving standard Zn treatment. Shoot Zn concentrations were positively correlated with tiller numbers at normal N levels. High N attenuated the positive effect of Zn on rice tillering at low temperatures due to higher shoot Zn and IAA accumulation, and lower tiller buds CTK/IAA ratios. However, appropriate Zn application under high N levels was conducive to breaking tiller dormancy and promoting tillering growth spurts when recovering to normal temperature, which was related to the synergistic regulation of hormone balance and nutrient absorption by N and Zn. In conclusion, Zn could enhance rice low‐temperature stress resilience and facilitate tiller recovery via balancing the hormones in tiller buds. However, higher environmental N limited the stimulation of Zn on rice tillering under low temperature.

Antibiotic Resistance Gene Transformation and Ultrastructural Alterations of Lettuce (Lactuca sativa L.) Resulting from Sulfadiazine Accumulation in Culture Solution

The research herein explored the possible mechanism of toxicity of the antibiotic sulfadiazine (SD) and the related antibiotic resistance gene transformation in lettuce by systematically investigating its growth responses, ultrastructural changes, and antibiotic resistance gene transformation via solution culture experiments. The results showed that SD mainly accumulated in the roots of lettuce at concentrations ranging from 6.48 to 120.87 μg/kg, which were significantly higher than those in leaves (3.90 to 16.74 μg/kg). Lower concentrations of SD (0.5 and 2.0 mg/L) in the culture nutrient solution exerted little effect on lettuce growth, while at SD concentrations higher than 10 mg/L, the growth of lettuce was significantly inhibited, manifesting as shorter root length and lower dry matter yield of whole lettuce plants. Compared with that for the control group, the absolute abundance of bacteria in the root endophyte, rhizosphere, and phyllosphere communities under different concentrations of SD treatment decreased significantly. sul1 and sul2 mainly accumulated in the root endophyte community, at levels significantly higher than those in the leaf endophyte community. Studies of electrolyte leakage and ultrastructural characteristics of root and leaf cells indicated that lettuce grown in culture solutions with high SD concentrations suffered severe damage and disintegration of the cell walls of organs, especially chloroplasts, in leaves. Furthermore, the possible mechanism of SD toxicity in lettuce was confirmed to start with the roots, followed by a free flow of SD into the leaves to destroy the chloroplasts in the leaf cells, which ultimately reduced photosynthesis and decreased plant growth. Studies have shown that antibiotic residues have negative effects on the growth of lettuce and highlight a potential risk of the development and spread of antibiotic resistance in vegetable endophyte systems.

Root growth response of serradella species to aluminium in solution culture and soil

AbstractSerradella (Ornithopus) species are high‐quality pasture legumes that originate from the Mediterranean basin and have been increasingly used in southern Australian temperate grazing systems. They are generally regarded as tolerant of soils with low pH and, by inference, elemental toxicities such as aluminium (Al). No studies have examined the effect of high Al concentrations on the growth of French serradella (Ornithopus sativus Brot.) or newly developed cultivars of yellow serradella (O. compressus L.). Several cultivars/accessions of each species were grown in low ionic‐strength nutrient solutions at pHCa 4.5 containing a range of Al concentrations. Their susceptibility to root growth inhibition by Al was benchmarked against reference species ranging from Al‐sensitive to Al‐tolerant. Most serradella cultivars had moderate‐to‐high Al tolerance in solution culture but one yellow and two French serradella cultivars ranked alongside the Al‐sensitive reference species. A subset of cultivars and reference species were then grown in an Al‐toxic soil to test the validity of the solution culture results; these cultivars spanned the apparent range in Al sensitivity/tolerance indicated by the solution culture experiment. Variation in the relative root length achieved in Al‐toxic solution culture explained ~59% of the variation in the relative root length achieved in the acidic Al‐toxic soil. This result supports the conclusion that Al tolerance varies among serradella and that some cultivars may not thrive in soils with pHCa < 4.5 and elevated extractable Al concentrations.

Applications of copper and silver nanoparticles on wheat plants to induce drought tolerance and increase yield.

Drought adversely affects the yield, quality and nutritional value of the crop plants. Additionally, it causes unrest in society and economic loss to the farmers and governments. The present study involved the applications of nanoparticles to induce drought tolerance and improve yield in the wheat (Triticum aestivum L.) plants. Green chemical methods were used for the synthesis of silver nanoparticles (AgNPs) and copper nanoparticles (CuNPs). CuNPs were used in 0, 3, 5 and 7 mg/L and 0, 10, 20 and 30 mg/L of AgNPs were tested at −4, −6 and −8 bars osmotic potential in laboratory experiments and 40%, 60% and 80% field capacity (FC) in the glasshouse experiments were maintained. The solution culture experiments revealed significantly higher chlorophyll stability index (CSI), leaf succulence (LS) and leaf K (LK) content in plants treated with 03 mg/L of CuNPs and 10 mg/L of AgNPs, indicated the positive role of CuNPs and AgNPs in drought tolerance of wheat. A similar trend was observed for stomatal conductance (SC) and morphological parameters with the applications of Cu and Ag nanoparticles at different levels of field capacity. The results of this study provide the experimental evidence to use CuNPs and AgNPs to induce drought resistance and improve yield in the wheat plants by a satisfactory increase in nutrients uptake and water retention.

No evidence of regulation in root-mediated iron reduction in two Strategy I cluster-rooted Banksia species (Proteaceae)

AimsNon-mycorrhizal species such as Banksia (Proteaceae) that depend on root exudates to acquire phosphorus (P) are prominent in south-western Australia, a biodiversity hotspot on severely P-impoverished soils. We investigated the consequences of an exudate-releasing P-mobilising strategy related to control of iron (Fe) acquisition in two Banksia species, B. attenuata R.Br. and B. laricina C. Gardner, that differ greatly in their geographical distribution and rarity.MethodsWe undertook solution culture experiments to measure root-mediated Fe reduction (FeR) in non-cluster and cluster roots at four stages of cluster-root development, and whole root systems for plants grown at 2 to 300 μM Fe (as Fe-EDTA). As a positive control, we used Pisum sativum (cv. Dunn) to validate the FeR assay.ResultsUnlike typical Strategy I species, both Banksia species showed no significant variation in FeR, for either cluster or non-cluster roots, when grown at a wide range of Fe supply. For roots of different developmental stages, we measured a range for B. attenuata cluster roots of 0.13 ± 0.03 to 1.29 ± 0.14 μmol Fe3+ reduced g−1 FW h−1 and 0.56 ± 0.11 to 1.10 ± 0.24 μmol Fe3+ reduced g−1 FW h−1 in non-cluster roots. Similarly, for B. laricina cluster-roots, FeR ranged from 0.22 ± 0.07 to 1.21 ± 0.37 μmol Fe3+ reduced g−1 FW h−1, and in non-cluster roots from 0.56 ± 0.11 to 0.71 ± 0.08 μmol Fe3+ reduced g−1 FW h−1. We also observed only minor differences for whole-root system FeR, and even though B. attenuata showed signs of leaf Fe deficiency in the 2 μM Fe treatment, its FeR was the lowest of both species across all treatments at 0.079 ± 0.009 μmol Fe3+ reduced g−1 FW h−1, compared with the fastest rate of 0.20 ± 0.014 μmol Fe3+ reduced g−1 FW h−1 for B. laricina in the 28 μM Fe treatment. Taking plants through a pulse from low to high Fe, then back to low Fe supply did not elucidate any significant response in FeR.ConclusionsAlthough Fe acquisition is tightly controlled in the investigated Banksia species, such control is not based on regulation of FeR, which challenges the model that is commonly accepted for Strategy I species.

Exogenous Zinc Induced NaCl Tolerance in Okra (Abelmoschus Esculentus) by Ameliorating Osmotic Stress and Oxidative Metabolism

ABSTRACT Zinc appeared to be an important modulator with specific functions in plant physiology and increase resistance against different abiotic stresses. Many advances regarding role of zinc under abiotic stress in plants have been made since its revelation, therefore, present study was intended to understand the ameliorating role of zinc on morpho-physiological and biochemical responses of the okra varieties (Anmol and Haseena) when exposed to salt stress. A solution culture experiment was conducted to understand the protective role of zinc in relation to growth, physiological, ionic and antioxidant attributes in two okra varieties under saline condition. The growth medium was salinized with three salinity (Control, 80 mM L−1 and 160 mM L−1 NaCl) and one zinc level (30 µM L−1) applied exogenously in combine and sole form. Salt stress significantly reduces plant dry matter accumulation, chlorophyll contents, relative water contents (RWC), membrane stability index (MSI), K+/Na+ ratio and activities of antioxidant enzymes (POD, SOD, APX, CAT) and these effects are more prominent at high salt level (160 mM). Addition of zinc-alleviated salt toxicity is more conspicuous in okra variety Anmol as compared to variety Haseena as demonstrated by increasing RWC, MSI, K/Na ratio and activities of antioxidant enzymes. Our results suggested that zinc induced salt tolerance in Okra which can serve as a potential source to get sustainable production from salt-affected lands.

Partitioning of arsenic in low and high arsenic accumulating rice (Oryza sativa) cultivars

In view of limited information, an attempt has been made to work out the distribution pattern of arsenic (As) between root and shoot of high and low grain-As accumulating rice cultivars (HAC and LAC, respectively). For this purpose, a solution culture experiment was conducted at ICAR-Indian Agricultural Research Institute, New Delhi during kharif 2018-19 with two doses of As (@ 0 and 100 µg/L) and four rice cultivars comprising one HAC (IR-36) and three LACs (Khitish, Satabdi and Badshabhog). Results indicated that the biomass yields were not affected either by As or by cultivars. The highest root As content was recorded with Khitish (4.64 mg/kg), whereas, IR-36 showed the lowest value (2.00 mg/kg) but shoot As content did not vary with cultivars. Cultivars followed almost similar trends for As uptake. The highest translocation coefficient of As from root to shoot ranged from 0.52 (IR-36) to 0.31 (Khitish). It is clear from the study that LACs are more efficient in storing As in root, even though they uptake higher amount of As at the initial phase of growth, whereas, As is mobilized from root to above ground parts more efficiently in case of HACs. Thus, partitioning of As between root and shoot appears to be an important characteristic of rice (Oryza sativa L.) cultivars responsible for differential accumulation of As.

Effects of Al stress on the growth and nitrogen uptake of maize varieties with different Al tolerance as related with Al chemical forms on root surfaces

To examine the effects of Al stress on the growth and nitrogen (N) absorption of maize varieties with different Al tolerance as related with chemical Al forms on maize root surfaces. Three maize cultivars, Al-tolerant cultivar Taiyu 1, medium-Al-tolerant cultivar Zhengdan 958, and Al-sensitive cultivar Denghai 11, were selected for short-term and long-term Al stress with solution culture experiments. After germination, the healthy and consistent seedlings were selected for root elongation measurement. The maize seedlings were put in the Hoagland nutrient solution for 7 and 21 days to measure N absorption efficiency by maize varieties and Al chemical forms on maize roots. Al stress inhibited the growth of maize, and the degree of the inhibition was positively correlated with the amount of Al accumulation on maize roots significantly (P < 0.05). The amount of Al accumulated on roots of Denghai 11 was the highest, followed by Zhengdan 958, while that of Taiyu 1 was the lowest, which was consistent with their tolerance to Al toxicity. In addition, only N absorption efficiency of the maize cultivars was inhibited, and their N accumulation was not affected by Al stress in the early stage of long-term Al stress. However, both N absorption efficiency and N accumulation of the maize cultivars were inhibited in the late stage of long-term Al stress, and the inhibition degree increased with the increase of Al concentration. Al stress showed the greatest inhibition on Al-sensitive cultivar of Denghai11. After Al stress, the Al adsorbed on maize roots was differentiated into exchangeable, complexed, precipitated, and residual Al. In the early stage of long-term Al stress, the content of complexed Al was the highest, followed by residual Al and exchangeable Al, and the precipitated Al was the lowest, while at the late stage of Al stress, the content of residual Al was the highest, followed by complexed Al. Correlation analysis showed that the chemical forms of Al on maize roots affected N absorption efficiency. Among them, the exchangeable Al and residual Al were the main Al forms that affected the nitrate-N absorption efficiency of maize roots. They showed greater influence on the Al-sensitive cultivar of maize than the Al-tolerant cultivar. Reducing adsorption and accumulation of Al on maize roots could decrease the inhibition of Al stress on N absorption efficiency and accumulation by maize, especially for Al-sensitive cultivar.

EFFECT OF SEQUENTIAL CONCENTRATIONS OF ZINC AND ITS COMBINATION WITH CALCIUM OR GLUTATHIONE ON THE GROWTH, WATER RELATIONS AND ANATOMY OF ROOTS, STEMS AND LEAVES OF PHASEOLUS VULGARIS CV. CONTENDER

Zinc (Zn) is one of the eight essential micronutrients. It is needed by plants in small amounts, but yet crucial to plant development. A solution culture experiment was conducted to study the variation in growth, water relations and anatomy of roots, stems and leaves of Phaseolus vulgaris cv. contender treated with 1, 200, 400, 600, 800, 1000and 1200 mMZnSO4. Maximum significant deplete in parameters of growth (Length of root and shoot; fresh and dry weights, relative growth rate; No of leaves and leaf area), stomatal index and rate of transpiration was observed with, 200, 400, 600, 800, 1000and 1200 mM ZnSO4. These effects were improved by the addition of Ca2+than the addition of glutathione at 10 mM. Moreover, there were a significant increase at low concentration (1mM) treatment. Width of root, width of cortex and width of vascular bundles were increase with increasing Zn concentrations either alone or in combination with glutathione &gt;Ca (NO3)2. For stem, the No of vascular bundles were decreased with increase in Zn concentration alone and with Ca (NO3)2, meanwhile increase with glutathione. Width of cortex and No of its rows were decrease with increase Zn concentrations. For leaves, the thickness of leaf blade, mid rib and vascular bundle were increase with increase the Zn concentrations alone, On other hands, they records a significant decrease in combination of Zn with Ca(NO3)2 or glutathione . In general, an increase in total uptake of zinc with increasing the concentration of Zn in all treatments. However, Ca (NO3)2 decrease these amounts than glutathione.

Differential Regulation of Kernel Set and Potential Kernel Weight by Nitrogen Supply and Carbohydrate Availability in Maize Genotypes Contrasting in Nitrogen Use Efficiency.

Sub-optimal nitrogen (N) conditions reduce maize yield due to a decrease in two sink components: kernel set and potential kernel weight. Both components are established during the lag phase, suggesting that they could compete for resources during this critical period. However, whether this competition occurs or whether different genotypic strategies exist to optimize photoassimilate use during the lag phase is not clear and requires further investigation. We have addressed this knowledge gap by conducting a nutrient solution culture experiment that allows abrupt changes in N level and light intensity during the lag phase. We investigated plant growth, dry matter partitioning, non-structural carbohydrate concentration, N concentration, and 15N distribution (applied 4 days before silking) in plant organs at the beginning and the end of the lag phase in two maize hybrids that differ in grain yield under N-limited conditions: one is a nitrogen-use-efficient (EFFI) genotype and the other is a control (GREEN) genotype that does not display high N use efficiency. We found that the two genotypes used different mechanisms to regulate kernel set. The GREEN genotype showed a reduction in kernel set associated with reduced dry matter allocation to the ear during the lag phase, indicating that the reduced kernel set under N-limited conditions was related to sink restrictions. This idea was supported by a negative correlation between kernel set and sucrose/total sugar ratios in the kernels, indicating that the capacity for sucrose cleavage might be a key factor defining kernel set in the GREEN genotype. By contrast, the kernel set of the EFFI genotype was not correlated with dry matter allocation to the ear or to a higher capacity for sucrose cleavage; rather, it showed a relationship with the different EFFI ear morphology with bigger kernels at the apex of the ear than in the GREEN genotype. The potential kernel weight was independent of carbohydrate availability but was related to the N flux per kernel in both genotypes. In conclusion, kernel set and potential kernel weight are regulated independently, suggesting the possibility of simultaneously increasing both sink components in maize.

Interactions between cadmium and zinc in uptake, accumulation and bioavailability for Salix integra with respect to phytoremediation

The willow (Salix spp.) is a potential accumulator of cadmium (Cd)/zinc (Zn), and the interaction between Cd and Zn is an important factor influencing their phytoextraction potentials. In this study, interactions between Cd and Zn in uptake, accumulation and bioavailability for Salix integra clone SI63 were investigated through nutrient solution and soil culture methods. The result of the soil culture showed that Cd had additive effects for Zn-caused biomass reduction. The result from nutrient solution indicated that added Zn showed antagonistic (low Cd level) or synergistic (moderate and high Cd levels) effects on shoot Cd accumulation and antagonistic effects on root Cd accumulation. Irrespective of nutrient solution or soil culture experiment, Cd addition always had antagonistic effects on Zn accumulation in both shoots and roots. Under Cd10Zn50 condition, the clone accumulated higher Cd and Zn concentrations (95 μg g−1 Cd and 165 μg g−1 Zn) in shoots. Cd slightly increased bioavailable Zn in the rhizosphere, and EDTA well predicted bioavailable Cd and Zn in the rhizosphere. Interactions of Cd–Zn markedly changed their respective phytoextraction potentials, especially for Zn. This result will provide a new insight into improving phytoextraction potentials of both Cd and Zn using willows through applying metal interactions.

Impact of foliar and root application of phosphorus on zinc concentration of winter wheat grown in China

Foliar zinc (ZnSO4) application is an effective agronomic tool for Zn biofortification of wheat (Triticum aestivum L.) and hence for overcoming human Zn deficiency. It is unclear how the methods used to apply phosphorus (P) fertilisers affect the uptake and availability of Zn in wheat plants. Here, a solution-culture experiment and a 2-year field experiment were conducted to determine the influence of P applied to leaves or roots on total, soluble and insoluble Zn in winter wheat plants (cv. Xiaoyan-22) also receiving foliar Zn. Foliar Zn application, regardless of P application, significantly improved grain total Zn (primarily water-soluble) by 79.4% under both growth conditions, and reduced grain phytic acid:Zn (PA:Zn) molar ratio by 54.4% in the field. In solution culture, root-applied P did not affect plant uptake of foliar-applied Zn; however, foliar application of Zn plus P reduced the soluble fraction of Zn in wheat tissues, and thus decreased grain Zn concentration by 13.2% compared with Zn-only foliar application. Similarly, in the field, foliar-applied Zn plus P resulted in lower grain total and soluble Zn concentration and higher grain PA and PA:Zn molar ratio than foliar Zn alone. Overall, foliar Zn application is efficient in increasing grain Zn concentration and bioavailability under varied methods of P application. Although foliar-applied P slightly reduces the ability of plants to use foliar-applied Zn to increase grain Zn, foliar Zn combined with commonly applied foliar P application represents an easily adoptable practice for farmers that will help to alleviate Zn deficiency in human populations.

Benzo(a)pyrene inhibits the accumulation and toxicity of cadmium in subcellular fractions of Eisenia fetida

Cadmium (Cd) and benzo [a]pyrene (BaP) often co-occur in the environment, and the critical body residue of organisms is used as an indicator of the toxic effects of contaminants. However, little is known about their distributions and toxicities when pollution of Cd and BaP are combined. Semi-static solution culture experiment was used to study the impacts of BaP on the subcellular distribution of the toxic metal Cd in the earthworm Eisenia fetida. We explored the mechanisms by which this organism responds to combined exposure to these pollutants by measuring the protein content of each of three subcellular fractions, as well as acetylcholinesterase (AChE) and glutathione S-transferase (GST) activities. The subcellular partitioning of Cd was heterogeneous and Cd mainly accumulated in the cytosolic fraction (Fraction C), which was previously reported to be involved in metal immobilization. In Fraction C, Cd accumulation was correlated with the external concentration to which the earthworm had been exposed; however, in the presence of BaP, Cd accumulation was inhibited and plateaued at high external Cd concentrations. A principal component analysis revealed that this decreased Cd accumulation might be caused by increases in GST activity, which likely increased the excretion of Cd. BaP was also found to stimulate protein biosynthesis and upregulate AChE and GST activities in the debris fraction (Fraction E), indicating other potential detoxification mechanisms in this fraction. Granule fraction (Fraction D) had a lower protein content, AChE and GST activities than the other subcellular fractions, supporting previous findings that Fraction D is largely inert.