Response of wheat genotypes to foliar spray of ZnO and Fe2O3 nanoparticles under salt stress

This study evaluated the effects of iron oxide (Fe₂O₃) and zinc oxide (ZnO) on two wheat genotypes (Kavir and Tajan) at three levels (0, 75, and 150 mM sodium chloride (NaCl)) of salinity. Spray treatments included two forms of normal and nanoparticles of Fe₂O₃ and ZnO, a mixture of nanoparticles of Fe₂O₃ and ZnO (2 g L^?1) and a non-spray treatment. The pot experiment was arranged as factorial in a randomized complete block design with four replications. Two forms of Fe₂O₃ and ZnO significantly accelerated plant height, leaf area, shoot dry weight, and the concentration of iron (Fe) and zinc (Zn) in comparison with non-spray treatment. The highest plant height and leaf Fe concentration belonged to Fe₂O₃ nanoparticles; however, it seems that the spray of nanoparticles may not be superior compared with normal forms in alleviation of salinity impacts.     

Effectiveness of Fe3+-citrate and Fe3+-edta in ameliorating arsenic-toxicity (chlorosis) in hydroponic rice

Effectiveness of iron (Fe³⁺)-citrate and Fe³⁺-EDTA (ethylenediaminetetraacetic acid) in reducing arsenic (As)-toxicity in rice was evaluated. The treatments: 1) 0 µM As + 10 µM Fe³⁺-citrate (control), 2) 13.4 µM As + 10 µM Fe³⁺-citrate (As-treated), 3) 13.4 µM As + 10 µM Fe³⁺-citrate + 40 µM Fe³⁺-citrate (additional Fe³⁺-citrate), and 4) 13.4 µM As + 10 µM Fe³⁺-citrate + 40 µM Fe³⁺-EDTA (additional Fe³⁺-EDTA) were studied for 14 days. Chlorosis was found in the young leaves of the As-treated plants. Additional Fe³⁺-citrate failed to remediate the chlorosis, however, additional Fe³⁺-EDTA removed the chlorosis almost completely, indicating that the effectiveness of Fe³⁺-EDTA was much higher than Fe³⁺-citrate. The Fe³⁺-EDTA treated plants were greener than the additional Fe³⁺-citrate treated plants. Iron concentration in the shoots of additional Fe³⁺-EDTA plants was much higher than that of additional Fe³⁺-citrate plants, indicating that Fe³⁺-EDTA might have been more readily available to the plants roots than Fe³⁺-citrate.     

Differences in Response to Iron Deficiency Among Some Lines of Common Bean

Abstract

Five dry bean cultivars (Coco blanc, Striker, ARA14, SVM29‐21, and BAT477) were evaluated for their resistance to iron deficiency on the basis of chlorosis symptoms, plant growth, capacity to acidify the external medium and the root‐associated Fe³⁺‐reduction activity. Plants were grown in nutrient solution supplied or not with iron, 45 µM Fe(III)EDTA. For all cultivars, plants subjected to iron starvation exhibited Fe‐chlorosis. These symptoms were more severe and more precocious in BAT477 and Coco blanc than in the others cultivars. An important acidification of the culture medium was observed between the 4th and the 8th days of iron starvation in Striker, SVM29‐21 and, particularly, ARA14 plants. However, all Fe‐sufficient plants increased the nutrient solution pH. This capacity of acidification appeared more clearly when protons extrusion was measured in 10 mM KCl + 1 mM CaCl₂. The above genotypic differences were maintained: ARA14 showed the higher acidification followed by Coco blanc and BAT477. Iron deficiency led also to an increase of the root‐associated Fe(III)‐reductase activity in all lines. However, genotypic differences were observed: Striker shows the highest capacity of iron reduction under Fe deficiency condition.     

Effects of nano Fe/SiO2 fertilizers on germination and growth of barley and maize

Iron (Fe) nanoparticles (NPs), with 30–40 nm diameter, were stabilized on sand. The resulting synthesized Fe/SiO₂ NPs, with different Fe contents (0–25 mg kg^?1) were employed as fertilizers in probing the mean germination time (MGT), growth and dry matter of barley and maize and their comparison with common Fe/SiO₂ in a completely randomized design (CRD) experiment. The results showed that our fertilizers had significant effects on MGT, with the lowest of 0.58 day for barley and 0.79 day for maize; at 15 and 5 mg kg^?1 nano Fe/SiO₂, respectively. Application of 15 mg kg^?1 of nano Fe/SiO₂ increased the shoot length: 8.25% and 20.8% for barley and maize, respectively. However, the concentration of 25 mg kg^?1 had a negative impact on shoot length in barley. Increasing the concentrations of both nano and common Fe/SiO₂ particles, increased the root lengths in both plants, however this increase was higher with the application of nano Fe/SiO₂. Likewise, seedling length enlarged with the concentration increase of both Fe/SiO₂ particles and was more pronounced with nano Fe/SiO₂. The application of nano Fe/SiO₂ was more effective compared with the common Fe/SiO₂ in encouraging barley and maize growth. The positive impact was higher in maize than barley.     

Leaf Responses to Reduced Iron Availability in Two Tomato Genotypes: T3238FER (Iron Efficient) and T3238fer (Iron Inefficient)

Abstract

The present work is aimed at evaluating some effects induced by different levels of iron availability in the growth medium for two different tomato (Lycopersicon esculentum Mill.) genotypes, the T3238fer (Tfer), unable to activate mechanisms for iron mobilization and uptake known as “strategy I,” and its correspondent wild‐type T3238FER (TFER). By using different iron concentration in the growth solution, the most suitable iron level to induce phenotypic differences between the two genotypes without being lethal for the mutant was found to be 40 µM Fe‐Na‐EDTA. The analyses were carried out also on plants grown with 80 µM Fe‐Na‐EDTA, an iron concentration at which the two genotypes showed no phenotypic differences. A significant decrease in total leaf iron and chlorophyll content was detected in both genotypes following reduction of iron concentration in the nutrient solution, and was particularly evident in Tfer40, which showed symptoms of chlorosis. The photo‐electron transport rate of the whole chain was significantly affected by growth conditions as well as by genotype, the lowest activity being detected in Tfer40 plants. Chlorophyll a fluorescence analysis revealed an increase in non‐photochemical quenching (q _NP) of Tfer plants grown at both iron concentrations, indicating the activation of photoprotective mechanisms, which, however, were not sufficient to prevent photoinhibition when plants were grown at 40 µM iron, as indicated by significant reduction in PSII photochemistry (F _v/F _m) and photochemical quenching (q _P). The actual quantum yield of PSII (Φ_PSII) and the intrinsic PSII efficiency (Φ_EXC) showed the same behavior of q _P and F _v/F _m ratio. A significant effect of mutation and iron supply on all the pigments was detected, and was particularly evident in the mutant grown at 40 µM iron. A different behavior was shown by the three pigments involved in the xantophyll cycle, violaxanthin being less affected than chlorophylls and the other carotenoids, and zeaxanthin even increasing, due to the xanthophyll cycle activation. In conclusion, the interaction between iron deprivation and fer mutation induced functional alterations to the photosynthetic apparatus. Anyway, as far as concerns the photo‐electron transport activity, the influence of fer mutation seemed to occur independently from iron supply.     

Effects of bicarbonate and different Fe sources on vegetative growth and physiological characteristics of bell pepper (Capsicum annuum L.) plants in hydroponic system

In order to determine the best iron (Fe) sources under alkaline conditions, an factorial experiment was conducted based on a completely randomized design with two factors of Fe fertilizer at four forms [iron sulfate (FeSO₄), Fe- ethylenediaminetetraacetic acid (EDTA), Fe- diethylenetriaminepentaacetic acid (DTPA) and Fe- ethylenediamine-N,N’-bis (EDDHA), and sodium bicarbonate (NaHCO₃)] at three levels (0, 10 and 15 mM) with three replications. Results showed that the highest loss of vegetative growth (stem length, leaf number, leaf area, stem diameter, and leaf, stem and root dry weight) and ecophysiological parameters (F_v/F_m, SPAD and RWC) was observed in plants treated with FeSO₄. Alkalinity stress increased proline concentration especially in FeSO₄ treatment. Bicarbonate treatments decreased Fe concentration in plant tissues. Fe-EDTA and Fe-DTPA fertilizer sources acted similar or even better than EDDHA at 10 mM NaHCO₃ concentration, but the best Fe fertilizer source was Fe-EDDHA at 15 mM NaHCO₃ concentration.     

Effect of interaction between salinity and nanoparticles (Fe2O3 and ZnO) on physiological parameters of Zea mays L.

A pot experiment was conducted to evaluate the effects of zinc oxide (ZnO) and iron oxide (Fe₂O₃) nanoparticles on the growth of two maize cultivars under the saline condition. Salt stress induced decreases of shoot, root dry weight, leaf area and leaf gas exchange of S.C. 704 more than Bulk. The increase of salinity level, chlorophyll a, b and total chlorophyll content and iron (Fe) and zinc (Zn) concentrations under all spray treatments declined. Application of ZnO and Fe₂O₃ significantly enhanced the root growth (17%), net carbon dioxide (CO₂), assimilation rate (8%) and sub-stomatal CO₂ concentration (5%) of maize compared to control. Nanoparticles of Fe₂O₃ and ZnO caused an increase in leaf Fe (22%) and Zn (11%) concentrations, respectively, compared with normal forms. According to the results, although the alleviation effects of Zn and Fe have been demonstrated under stress conditions, nanoparticles were more effective than normal forms, which may be due to their shape, size, distribution and characteristics.     

Influence of Selenium on Cadmium Toxicity in Cucumber (Cucumis sativus cv. 4200) at an Early Growth Stage in a Hydroponic System

An experiment was established to assess the ability of selenium (Se) to reduce cadmium (Cd) toxicity when tomato was grown hydroponically. A factorial experiment was arranged in a completely randomized design with six replicates in cucumber (Cucumis sativus cv. 4200). The Se was applied at four levels [0 mg L^–1 (Se0), 2 mg L^–1 Se (Se1), 4 mg L^–1 Se (Se2), and 6 mg L^–1 Se (Se3)], whereas Cd was applied at three levels [0 µM Cd (Cd0), 5 µM Cd (Cd1), and 7 µM Cd (Cd2)]. The Se improved the dry weight of roots even when plants were exposed to Cd. Treatment Se1 improved the dry weight of shoots in Cd1 and Cd2. Treatments Se1 and Se2 improved photosynthesis in Cd1. Treatment Se1 significantly improved stomatal conductance in Cd2 at all levels of Se relative to Cd2. The greatest Cd concentration in leaves was observed in Cd2 × Se0 and while Se concentration in solution increased in response to Se1, Se2, and Se3. The greatest Se level reduced Cd uptake the most. Growth and photosynthetic attributes can be negatively affected by Cd, but Se has the ability to buffer, or improve, several attributes.     

Effects of NaHCO3 on photosynthetic characteristics,and iron and sodium transfer in pomegranate

In order to study effects of sodium bicarbonate (NaHCO₃) stress in irrigation water on photosynthetic characteristics and iron (Fe) and sodium (Na⁺) translocation content of pomegranate plants, a factorial experiment was conducted based on completely randomized design with three cultivars of pomegranate (“Gorch-e-Dadashi,” “Zagh-e-Yazdi,” and “Ghermez-e-Aliaghai”) and four concentrations of NaHCO₃ (0, 5, 10, and 15 mM), with three replications. The results of plant analysis indicated that NaHCO₃ affected chlorophyll index, F_v/F_m, and performance index (PI) in upper and lower leaves of shoots and also the translocation of Na⁺ and Fe. The results also showed that Fe translocation from root to shoot reduced at 15 mM level of NaHCO₃. The highest Na translocation and the lowest Fe translocation were observed in Zagh-e-Yazdi and Ghermez-e-Aliaghai cultivars, respectively. The ratio of sodium/potassium (Na⁺/K⁺) in stems was higher than that in roots and leaves, and the observed chlorophyll content of upper leaves was also lower than that of lower leaves. Based on the measured parameters Gorch-e-Dadashi cultivar showed less relative sensitivity than other cultivars to NaHCO₃ of irrigation water through maintaining the lower Na⁺ transport to the shoots, and improvement of Fe transport to shoots.     

Mesoporous SBA-15 Supported Iron Oxide: A Potent Catalyst for Hydrogen Sulfide Removal

A novel silicate mesoporous material, SBA-15 supported Fe₂O₃, was synthesized by post-synthesis method via ultrasonic-assisted route. The desulfurization test from a gas mixture containing 0.1 vol% H₂S was carried out over SBA-15 supported Fe₂O₃ in a fixed-bed system at atmospheric pressure and room temperature. The effects of the chemical nature of Fe₂O₃ and the textural properties of the material on desulfurization capacity were studied. Materials before and after the desulfurization test were characterized using nitrogen adsorption, XRD, TEM, FTIR, XPS, ICP and other standard methods. The characterization results suggest that modification process does not change the two-dimensional hexagonal mesostructure of SBA-15. Iron species disperses inside channels and the outside surface in the crystalline phase of iron oxide. The material with iron content of 31.3 wt% presented highest H₂S uptake capacity. Structural properties of the material also play important roles in desulfurization performance besides the catalytic effects of iron oxide. The basic feature of material and enough oxygen supply are benefit for the reaction. SBA-15 supported Fe₂O₃ can be an effective alternative to capture H₂S from gas streams.     

Role of selenium in mitigation of cadmium toxicity in pepper grown in hydroponic condition

Selenium (Se) is an essential element for humans but is not considered as essential for plants. However, its beneficial role in improving plant growth and stress tolerances is well established. In order to study the role of Se in cadmium (Cd) toxicity in pepper (Capsicum frutescens cv. Suryankhi Cluster), this experiment was carried out in greenhouse conditions. Treatments comprised Cd [0, 0.25, and 0.5 mM cadmium chloride (CdCl₂)] and Se [0, 3, and 7 µM sodium selenite (Na₂SeO₃)] with three replications. The result showed that Cd decreased chlorophyll a, chlorophyll b, and carotenoids, whereas Se supplementation diminished Cd toxicity on photosynthetic pigment. Selenium at 7 µM significantly increased the leaf area in the plants grown at 0.25 mM Cd. The application of Se at 3 µM with 0.25 mM Cd and Se at 3 µM and Se at 7 µM with 0.5 mM Cd increased the activity of catalase (CAT). Selenium at 7 µM decreased the proline content of pepper leaves exposed to Cd at 0.5 mM (30%). Selenium significantly enhanced the antioxidant activity of leaves, which was diminished by Cd toxicity. In general, Se has a beneficial effect on plant growth and is an antioxidant enzyme of pepper cv. Suryankhi Cluster under Cd stress and non-stress conditions.     

Iron fertilizers applied to calcareous soil on the growth of peanut in a pot experiment

A greenhouse pot experiment was conducted with peanuts (Arachis hypogaea L., Fabceae) to evaluate iron compound fertilizers for improving within-plant iron content and correcting chlorosis caused by iron deficiency. Peanuts were planted in containers with calcareous soil fertilized with three different granular iron nitrogen, phosphorus and potassium (NPK) fertilizers (ferrous sulphate (FeSO₄)–NPK, Fe–ethylendiamine di (o-hydroxyphenylacetic) (EDDHA)–NPK and Fe–citrate–NPK). Iron nutrition, plant biomass, seed yield and quality of peanuts were significantly affected by the application of Fe–citrate–NPK and Fe–EDDHA–NPK to the soil. Iron concentrations in tissues were significantly greater for plants grown with Fe–citrate–NPK and Fe–EDDHA–NPK. The active iron concentration in the youngest leaves of peanuts was linearly related to the leaf chlorophyll (via soil and plant analyzer development measurements) recorded 50 and 80 days after planting. However, no significant differences between Fe–citrate–NPK and Fe–EDDHA–NPK were observed. Despite the large amount of total iron bound and dry matter, FeSO₄–NPK was less effective than Fe–citrate–NPK and Fe–EDDHA–NPK to improve iron uptake. The results showed that application of Fe–citrate–NPK was as effective as application of Fe–EDDHA–NPK in remediating leaf iron chlorosis in peanut pot-grown in calcareous soil. The study suggested that Fe–citrate–NPK should be considered as a potential tool for correcting peanut iron deficiency in calcareous soil.     

Influence of nano-iron oxide and zinc sulfate on physiological characteristics of peppermint

To evaluate the impact of nano-iron oxide and zinc sulfate fertilizers on peppermint in field conditions, a factorial split experiment with two micro-nutrient fertilizers [Zinc (Zn) and Iron (Fe)] in RCBD with three replicates was conducted at University of Tehran, during 2014 and 2015. Fe at four levels (0, 0.25, 0.5, and 0.75 g L-1) and Zn at three levels (0, 2.5, and 5 g L-1) were applied. Fe and Zn fertilizer application significantly improved photosynthetic pigments, mineral nutrient content, essential oil concentration, and dry matter yield in peppermint. The highest iron content (1578.00 mg kg^?1) was achieved when 5 g L^?1 of Zn was applied along with 0.75 g L^?1 Fe. According to our results, the application of 2.5 g L^?1 of Zn plus 0.5 g L^?1 Fe fertilizers could be recommended to achieve the highest plant dry matter and essential oil yield.     

Predicting Initial Tall Fescue Root Growth Response to Calcium/Aluminum Solution Concentrations

A study was conducted to quantify effects of soluble aluminum (Al) and gypsum (CaSO₄) on initial root growth of three varieties of tall fescue (Festuca arundinacea). Experiments were performed in a growth chamber using hydroponic solutions containing Al from 0 to74 µM in combination with CaSO₄ at 0 to10 mM. Seedlings were grown for 7 d, harvested, air dried, scanned, and weighed for treatment comparisons. Significant differences in root length existed between varieties in Al‐only solutions at low Al concentrations. All varieties showed reduced root growth at concentrations greater than 37 µM Al. Increased calcium (Ca²⁺) and sulfate (SO₄ ^2?) at given concentrations of Al resulted in greater root growth. Relative root growth increased approximately 30% to >80% at 37 µM Al as CaSO₄ increased from 2.5 to 10 mM. A simple logistic model adequately described the effects of Al and CaSO₄ on root growth (r² = 0.86, 0.95, and 0.96 for the three varieties).     

Determination of Trace Amounts of Cadmium Ions in Water and Plant Samples Using Ligand-Less Solid Phase Extraction-Based Modified Co3O4 Nanoparticles

In this study, a new Co₃O₄ nanoparticles (NPs) coated with sodium dodecyl sulphate (SDS) is developed for preconcentration of trace amounts of cadmium ions (Cd ²⁺) as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The effects of various parameters, including pH of sample solution, amount of sorbent, flow rates of solution and eluent, sample volume, type, and least amount of the eluent for elution of the Cd ²⁺ from Co₃O₄ NPs were studied and optimized. Experimental conditions for effective separation of trace levels of the Cd ²⁺were optimized with respect to different experimental parameters in Column method. Under the best experimental conditions, the calibration curve was linear in the range of 1.0–500.0 ng.mL^?1 of cadmium (Cd) with R² = 0.999. The detection limit was 0.4ng.mL^?1 in the original solution (3S_b/m) and the relative standard deviation for eight replicate determination of 0.1µg.mL^?1 Cd was ±2.1%. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The developed method was successfully applied to the extraction and determination of Cd in water and food samples with satisfactory results.     

Physiological Effects and Fluorescence Labeling of Magnetic Iron Oxide Nanoparticles on Citrus (<Emphasis Type="Italic">Citrus reticulata</Emphasis>) Seedlings

Nanoparticles (NPs) have been reported to cause physiological effects on plant cells and tissue. This study traced the uptake and distribution of magnetic iron oxide nanoparticles (γ-Fe₂O₃ NPs) in citrus (Citrus reticulata) plants under hydroponic condition by fluorescent dye labeled γ-Fe₂O₃ NPs, and described a detailed evidence of physiological effects of 0–100 mg/L γ-Fe₂O₃ NPs on citrus plants by measuring the physiological parameters such as content of chlorophyll, malondialdehyde (MDA), soluble sugar, soluble protein, activity of antioxidant enzyme, and ferric reductase after 21 days exposure. Fluorescence images of citrus stem and root showed that citrus roots could absorb γ-Fe₂O₃ NPs but no translocation from roots to shoots was observed, since NPs aggregated or even clogged the vascular system. Physiological results showed that 20 mg/L γ-Fe₂O₃ NPs could significantly enhance chlorophyll content by 126.4%, while 50 and 100 mg/L of γ-Fe₂O₃ NPs decreased chlorophyll content by 27.8 and 35.4%, respectively. MDA contents in citrus leaves under 20–100 mg/L γ-Fe₂O₃ NPs exposure were increased by 37.8, 107.2, and 61.5%, respectively, while that in roots were decreased by 27.0,11.9, and 7.4%, respectively, with elevated SOD and CAT activity, suggesting that oxidative stress occurred in citrus leaves, but oxidative stress in roots was eliminated by antioxidant defense. It is noteworthy that although Fe(II)-EDTA treatment had a high level of chlorophyll content, it induced strong oxidative stress in citrus plants as well. Collectively, the various physiological responses of citrus plants to γ-Fe₂O₃ NPs exposure were closely correlated with the concentrations of NPs. γ-Fe₂O₃ NPs at proper concentrations, such as 20 mg/L, have the potential to ameliorate chlorosis of plants and be effective nanofertilizers for increasing agronomic productivity.     

Synthesis and Characterisation of Novel-Activated Carbon from Waste Biomass Pine Cone and Its Application in the Removal of Congo Red Dye from Aqueous Solution by Adsorption

The present study deals with the synthesis and subsequent application of Fe₃O₄@n-SiO₂ nanoparticles for the removal of Cr(VI) from aqueous solutions. Rice husk, an agrowaste material, was used as a precursor for the synthesis of nanoparticles of silica. Synthesized nanoparticles were characterized by XRD and SEM to investigate their specific characteristics. Fe₃O₄@n-SiO₂ nanoparticles were used as adsorbent for the removal of Cr(VI) from their aqueous solutions. The effects of various important parameters, such as initial Cr(VI) concentration, adsorbent dose, temperature, and pH, on the removal of Cr(VI) were analyzed and studied. A pH of 2.0 was found to be optimum for the higher removal of Cr(VI) ions. It was observed that removal (%) decreased by increasing initial Cr(VI) concentration from 1.36?×?10^-2 to 2.4?×?10^-2 M. The process of removal was found to be endothermic, and the removal increased with the rise in temperature from 25 to 45 °C. The kinetic data was better fitted in pseudo-second-order model in comparison to pseudo-first-order model. Langmuir and Freundlich adsorption capacities were determined and found to be 3.78 and 1.89 mg/g, respectively, at optimum conditions. The values of ΔG ⁰ were found to be negative at all temperatures, which confirm the feasibility of the process, while a positive value of ΔH ⁰ indicates the endothermic nature of the adsorption process. The present study revealed that Fe₃O₄@n-SiO₂ nanoparticles can be used as an alternate for the costly adsorbents, and the outcome of this study may be helpful in designing treatment plants for treatment of Cr(VI)-rich effluents.     

The Influence of Cadmium Toxicity on Some Physiological Parameters as Affected by Iron in Rice (Oryza Sativa L.) Plant

The effects of interaction between cadmium chloride (CdCl₂) and iron (Fe)- ethylenediaminetetraacetic acid (EDTA) were studied in rice plant. The seedlings of rice were treated with 0, 50, and 100 μM CdCl₂ supplemented with 5, 10 and 20 ppm Fe as Fe-EDTA for 30 days. Plants were grown under controlled condition. In all the plants treated with CdCl_2, growth parameters [relative leaf growth rate (RLGR), specific leaf area (SLA), and leaf water content area (LWCA)], soluble, and unsoluble sugars contents decreased. Addition of Fe-EDTA moderated cadmium effects. Under CdCl₂ stress without Fe, malondialdehyde (MDA) content, proline content, catalase (CAT) and peroxidase (POD) activity increased, however, in solutions containing both CdCl₂ and Fe-EDTA, MDA content, proline content and activities of antioxidant enzymes decreased. In 50 μM CdCl₂, total protein content increased but in 100 μM decreased. With increasing Fe in solutions containing CdCl₂, protein content decreased. The results indicated that with increasing Fe-EDTA in CdCl₂ treated plants, the effects of toxicity of Cd decreased.     

Phosphorus amendment decreased cadmium (Cd) uptake and ameliorates chlorophyll contents,gas exchange attributes,antioxidants, and mineral nutrients in wheat (Triticum aestivum L.) under Cd stress

A 28-day pot (sand culture) experiment was carried to evaluate the effects of phosphorus (P) application in alleviating Cd phytotoxicity in wheat plants. Different levels of P (0, 10, and 20 kg ha^?1) were applied without and with 100 µM Cd. The results showed that 100 µM Cd concentration decreased plant biomass, chlorophyll contents, gas exchange attributes, and mineral nutrients in wheat plants. Cadmium stress increased tissue Cd and H₂O₂ concentrations. The activities of superoxide dismutases (SOD), peroxidase (POD) enzymes, increased while the activities of catalase (CAT), ascorbic acid (AsA), α-tocopherol, and phenolics decreased under Cd stress. Phosphorus supply increased shoot biomass, leaf area, photosynthetic pigments, and mineral nutrients and decreased Cd and H₂O₂ concentrations in shoots. Phosphorus application improved antioxidant enzyme activities and gas exchange attributes which emerged as an important mechanism of Cd tolerance in wheat. We conclude that P application contributes to decreased Cd concentrations in wheat shoots and increased gas exchange attributes and antioxidant enzymes and could be implemented in a general scheme aiming at controlling Cd concentrations in wheat for sustained production of this important grain crop.     

O2 supports 3-phosphoglycerate-dependent O2 evolution in chloroplasts from spinach leaves

We tested the hypothesis that the Mehler-ascorbate peroxidase (MAP) pathway supports 3-phosphoglycerate (PGA)-dependent oxygen (O₂) evolution using intact chloroplasts. Lowering O₂ concentration (<1?µM) suppressed PGA-dependent O₂ evolution rate. High O₂ concentration (about 250?µM) enhanced the electron fluxes in Photosystem II (PSII). Also, high O₂ concentration oxidized both Q_A in PSII and Cyt f in thylakoid membranes. These results indicated that the MAP pathway stimulated photosynthetic electron transport. Furthermore, electrochromic shift signal was also increased at high O₂ concentration, compared to low O₂ concentration. Non-photochemical quenching of chlorophyll fluorescence was also enhanced at high O₂ concentration. These data support our hypothesis that the MAP pathway functioned in intact chloroplasts and accelerated PGA-dependent O₂ evolution by inducing ΔpH formation to produce and supply adenosine triphosphate (ATP) to the conversion reaction of PGA to glyceraldehyde 3-phosphate through 1,3-diphosphoglycerate in chloroplasts.