The role of oxidative stress induced by growth regulators in the regeneration process of wheat

As part of work to optimize the regeneration processes of winter wheat callus culture the effects of two auxins (2,4-D, IAA), two cytokinins (kinetin, zeatin), and the fungal mycotoxin zearalenone, were tested individually in vitro using embryo-, and inflorescence-derived callus. To determine the role of oxidative stress in cell regeneration, changes in the basic antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidases (PODs) were investigated. In general, zearalenone (ZEN) was found to be more effective than cytokinin treatments for inducing shoot production, whereas auxins suppressed the regeneration process. Regenerating callus showed higher induction of these antioxidant enzymes in comparison with non-regenerating callus. SOD, CAT and POD activities were higher in callus derived from inflorescence than in callus derived from immature embryo. Activities of SOD, CAT and POD in culture derived from immature embryos were depending on type of growth regulator in medium. The highest enzyme activities were observed in non-regenerating tissues after auxins treatment and in regenerating tissues after cytokinins treatment. The effect of ZEN was similar to that of cytokinins. One MnSOD band and two Cu/ZnSOD bands were detected in all cultures. Changes in SOD izoform patterns occurred in callus culture on media with auxins and ZEN, but not on media with cytokinins. Our results suggest that callus regeneration is associated with reactive oxygen species production induced by specific growth regulators. Reactive oxygen species under the control of cellular antioxidant machinery can mediate signalling pathways between exogenously applied growth regulators and the induction and/or creation of the direction of morphogenesis.     

Adaptive responses of <Emphasis Type="Italic">Populus przewalskii</Emphasis> to drought stress and SNP application

In this study we used the cuttings of Populus przewalskii Maximowicz as experimental material and sodium nitroprusside (SNP) as nitric oxide (NO) donor to determine the physiological and biochemical responses to drought stress and the effect of NO on drought tolerance in woody plants. The results indicated that drought stress not only significantly decreased biomass production, but also significantly increased hydrogen peroxide content and caused oxidative stress to lipids and proteins assessed by the increase in malondialdehyde and total carbonyl contents, respectively. The cuttings of P. przewalskii accumulated many amino acids for osmotic adjustment to lower water potential, and activated the antioxidant enzymes such as superoxide dismutase, guaiacol peroxidase and ascorbate peroxidase to maintain the balance of generation and quenching of reactive oxygen species. Moreover, exogenous SNP application significantly heightened the growth performance of P. przewalskii cuttings under drought treatment by promotion of proline accumulation and activation of antioxidant enzyme activities, while under well-watered treatment the effect of SNP application was very little.     

Acquired tolerance of tomato (Lycopersicon esculentum cv. Micro‐Tom) plants to cadmium‐induced stress

The effects of varying concentrations of cadmium (Cd) on the development of Lycopersicon esculentum cv. Micro‐Tom (MT) plants were investigated after 40 days (vegetative growth) and 95 days (fruit production), corresponding to 20 days and 75 days of exposure to CdCl₂, respectively. Inhibition of growth was clearly observed in the leaves after 20 days and was greater after 75 days of growth in 1 mM CdCl₂, whereas the fruits exhibited reduced growth following the exposure to a concentration as low as 0.1 mM CdCl₂. Cd was shown to accumulate in the roots after 75 days of growth but was mainly translocated to the upper parts of the plants accumulating to high concentrations in the fruits. Lipid peroxidation was more pronounced in the roots even at 0.05 mM CdCl₂ after 75 days, whereas in leaves, there was a major increase after 20 days of exposure to 1 mM CdCl₂, but the fruit only exhibited a slight significant increase in lipid peroxidation in plants subjected to 1 mM CdCl₂ when compared with the control. Oxidative stress was also investigated by the analysis of four key antioxidant enzymes, which exhibited changes in response to the increasing concentrations of Cd tested. Catalase (EC 1.11.1.6) activity was shown to increase after 75 days of Cd treatment, but the major increases were observed at 0.1 and 0.2 mM CdCl₂, whereas guaiacol peroxidase (EC 1.11.1.7) did not vary significantly from the control in leaves and roots apart from specific changes at 0.5 and 1 mM CdCl₂. The other two enzymes tested, glutathione reductase (EC 1.6.4.2) and superoxide dismutase (SOD, EC 1.15.1.1), did not exhibit any significant changes in activity, apart from a slight decrease in SOD activity at concentrations above 0.2 mM CdCl₂. However, the most striking results were obtained when an extra treatment was used in which a set of plants was subjected to a stepwise increase in CdCl₂ from 0.05 to 1 mM, leading to tolerance of the Cd applied even at the final highest concentration of 1 mM. This apparent adaptation to the toxic effect of Cd was confirmed by biomass values being similar to the control, indicating a tolerance to Cd acquired by the MT plants.     

Assessing of tolerance to metallic and saline stresses in the halophyte Suaeda fruticosa: The indicator role of antioxidative enzymes

Many areas are simultaneously affected by high concentrations of salts and trace metal elements (TME), the latter constituting a serious threat to human health. In the present study, we determined the combined effect of high salinity and toxic levels of trace elements on physiological behavior of the halophytic species Suaeda fruticosa. Plants were cultivated for three months with an irrigation solution supplemented separately with different concentrations of Pb²⁺ and Zn²⁺ (0, 200, 400 and 600 μM) with and without 200 mM NaCl. Growth, total chlorophyll, water status and ion nutrition were quantified and antioxidant enzyme activities [ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and catalase (CAT)] were studied. Our results revealed that S. fruticosa has a strong ability to tolerate lead and zinc. This halophyte accumulated higher concentrations of TME in their roots. Growth parameters of S. fruticosa were not significantly affected by TME. An enhancement of Ca²⁺ concentration accompanied by a decrease of Mg²⁺ content was observed under Pb²⁺ or Zn²⁺ treatments whereas K⁺ content was not affected by TME. Of the antioxidant enzymes, the activity of CAT and APX was increased by metal stress. However, the activity of GPX was diminished by increasing TME concentrations. It was concluded that NaCl 200 mM had a positive impact on the response of S. fruticosa to Zn²⁺ toxicity, acting through a decrease in Zn absorption.     

Chromium stress induced oxidative burst in Vigna mungo (L.) Hepper: physio-molecular and antioxidative enzymes regulation in cellular homeostasis

Vigna mungo (L.) Hepper commonly known as blackgram is an important legume crop with good quality dietary proteins and vitamins. Low production of blackgram in the chromium rich soil of Odisha is a serious concern against its demand. Chromium (VI) was tested on V. mungo var. B3-8-8 at 100, 150, 200, 250 and 300 µM concentration on growth, anti-oxidative enzymes and chromium content at 15, 30 and 45 d of treatments. Seed germination and growth decreased with increase dose and duration. Cr uptake induced oxidative burst with significant increase of osmolytes was observed in cell at lower doses but failed to adjust homeostasis at higher dose. Increase of GPX and SOD and decrease of CAT was observed as dose dependent. Increased protein content was detected in < 200 µM Cr concentration whereas, significant decrease of protein was noted thereafter. Down regulation of proteins (29.2 kDa and 32.6 kDa) was observed at > 250 µM of Cr. Total Cr uptake was greater in root than in shoot which might be due to poor translocation of heavy metal or detoxification. Thus, blackgram was able to maintain homeostasis at lower concentrations of Cr by activating the cascade of enzymes following cellular detoxification mechanism.Supplementary InformationThe online version of this article contains supplementary material available at (10.1007/s12298-021-00941-3)     

Protective effect of jasmonic acid and potassium against cadmium stress in peas (Pisum sativum L.)

A combination of mineral nutrients and plant growth regulators should be assessed to improve crop performance under various abiotic stresses. There is a need to include plant growth regulators in fertilization regime of various crops along with essential mineral nutrients, especially when they are irrigated with polluted water with higher levels of heavy metals. The performance of pea was evaluated under cadmium (Cd) stress coupled with potassium (K) and jasmonic acid (JA) supplementation. The Cd stress (50 μM) was applied to soil (sandy loam) grown pea plants as basal dose after a month of sowing. The control and stressed plants were then supplemented with K (5 M), JA (0.5 mM) and their collective application along with control as distilled water. Cd stress showed a marked reduction in growth pattern, however, the collective supplementation sufficiently improved the growth pattern of stressed peas plants as evidenced by improvement in shoot length (cm), root length (cm), number of leaves per plant, leaf area (cm²), plant fresh and dry weight (gm). Potassium application under Cd stress significantly enhanced internodal distance (cm) while the number of seeds per pod and relative water contents remained nonsignificant. The applied treatment (JA + K) under Cd stress prominently improved enzymatic activities, which were measured as nitrate reductase activity (NRA), nitrite reductase activity (NiRA), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). Cd stress impacted the biochemical profile by enhancing antioxidant capacity (AC), antioxidant activity (AA), total phenols (TP), while reducing total soluble protein (TSP), chlorophyll ‘a’, chlorophyll ‘b’ and carotenoids. The combined application of JA and K under Cd stress enhanced AC, AA, TP, Chl a and b, TSP and carotenoids. The results indicate that foliar application of JA and K efficiently negated the harmful effects of Cd stress on peas.     

Influence of silicon on antioxidant mechanisms and lipid peroxidation in chickpea (Cicer arietinum L.) cultivars under drought stress

Abstract

The effects of exogenous silicon (Si) on leaf relative water content (RWC), and the growth, Si concentrations, lipid peroxidation (MDA), lipoxygenase (LOX) activity, proline and H₂O₂ accumulation, non-enzymatic antioxidant activity (AA) and the activity of some antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX) in shoots of ten chickpea cultivars grown under drought were investigated. Drought stress decreased the growth of all the cultivars while applied Si improved the growth at least five of the 10 chickpea cultivars. Silicon applied to the soil at 100 mg kg^?1 significantly increased Si concentrations of the cultivars and counteracted the deleterious effects of drought in 5 of the ten chickpea cultivars by increasing their RWC. In most cultivars tested H₂O₂, proline and MDA content and LOX activity were increased by drought whereas application of Si decreased their levels. APX activity was increased by drought but it was depressed by Si. In general, SOD and CAT activities of the cultivars were decreased by drought. Depending on cultivars, the CAT activity was decreased, and increased or unchanged in response to applied Si, while the SOD activity of the cultivars increased or unchanged by Si. The non-enzymatic antioxidant activity of the cultivars was also increased by Si. These observations implied an essential role for Si in minimizing drought stress-induced limitation of the growth and oxidative membrane damage in chickpea plants.     

Phytochemical and physiological changes in Salvia officinalis L. under different irrigation regimes by exogenous applications of putrescine

Water stress is the major factor limiting plant productivity and quality in most regions of the world. In the present study, a two-year field experiment was conducted to determine the influence of putrescine (Put) on phytochemical, physiological, and growth parameters of Salvia officinalis L. under different irrigation regimes. The highest stem dry weight (56.05 and 65.21 g m⁻²) plus leaf dry weight (124.51 g m⁻²) were predicted in irrigation regimes of (20 and 40%) plus 20% available soil water was depleted (ASWD), respectively. Total phenolic content (TPC) was increased significantly under the irrigation regime of 80% with the application of distilled water in spring. TPC showed an increasing trend with increases in Put concentration under all irrigation regimes in both spring and summer. The highest total flavonoids content (TFC) in wavelengths of 415 and 367 nm were predicted in 2.25 mM Put. The highest ascorbate peroxidase (APX) activity (0.13 μmol mg⁻¹ protein) was predicted in the irrigation regime of 20% with the application of distilled water in spring and summer. There was a significantly negative correlation coefficient between APX, TPC, and TFC. Indeed, there was a decreasing trend in APX and an increasing trend in TPC and TFC with increases in Put concentration under the irrigation regime of 20% ASWD. The highest hydroxyl radical scavenging activity (HRSA) values were obtained under irrigation regimes of 49.27% and 20% ASWD in spring and summer, respectively. There was an increasing trend in endogenous Put with increases in the Put concentration. The responses of compatible osmolytes to irrigation regime can be expressed by quadratic model, suggesting maximum proline (0.52 mg g⁻¹), total reducing sugars (TRS) (0.37 mg g⁻¹), xylose (0.68 mg g⁻¹), and mannose (0.37 mg g⁻¹) values would be obtained in irrigation regimes of 68.33%, 48.33%, 53.75%, and 56.25% ASWD, respectively.     

Effects of cold stress on glutathione and related enzymes in rat erythrocytes

Effects of acute and chronic cold stress on glutathione and related enzymes in rat erythrocytes were investigated. Blood from both cold-acclimated (CA) and cold-adapted (CG) rats had significantly lower concentrations of glutathione than blood from control animals. Superoxide dismutase activity was increased significantly in CA rats and tended to rise in CG rats. Activity of glutathione peroxidase in erythrocytes was inconsistent in that it tended to increase in CA rats but decreased significantly in CG rats. The results may imply that CG rats suffered deleterious effects of hydrogen peroxide. On the other hand, there were marked decreases in glutathione peroxidase and glutathione reductase activities in acutely cold-exposed rats in conjunction with unchanged levels of glutathione. In all treatments the state of riboflavin metabolism was estimated to be adequate, since no increases were observed in the erythrocyte glutathione reductase activity coefficient.     

Effect of copper on pro- and antioxidative reactions in radish (Raphanus sativus L.) in vitro and in vivo

The generation of superoxide radicals, lipid peroxidation (as measured by malone dialdehyde formation) and the activity of selected antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase) were assessed in radish (Raphanus sativus L.), in response to elevated concentrations of copper ions in the culture medium in vitro and in vivo. Experiments were performed on 7-day-old seedlings and 5-week-old calluses grown on media supplemented with CuSO₄ in concentrations of 10, 100 and 1000 μМ. The exposure to elevated Cu concentrations in the medium significantly reduced both callogenesis and the proliferation of radish calluses in vitro. Cu treatment resulted in the increased generation of the superoxide radical (O₂⁻) in radish seedlings and calluses indicating the occurrence of oxidative stress in radish cells, whereas the level of lipid peroxidation (LPO) remained unchanged. Both in calluses and in radish seedlings in vivo, the relative level of oxidative stress was maximal at micromolar Cu concentrations and became attenuated with increasing Cu concentrations. Stronger oxidative stress occurred in the radish seedlings in vivo, compared with radish calluses in vitro. The observed lower sensitivity of calluses to Cu-induced oxidative stress and their ability to proliferate upon exposure to Cu concentrations of up to 1000 μМ demonstrate the potential of in vitro cell-selection to obtain metal-tolerant radish plant lines.     

Efficiency of different types of biochars to mitigate Cd stress and growth of sunflower (Helianthus; L.) in wastewater irrigated agricultural soil

Cadmium contamination in croplands is recognized one of the major threat, seriously affecting soil health and sustainable agriculture around the globe. Cd mobility in wastewater irrigated soils can be curtailed through eco-friendly and cost effective organic soil amendments (biochars) that eventually minimizes its translocation from soil to plant. This study explored the possible effects of various types of plants straw biochar as soil amendments on cadmium (Cd) phytoavailability in wastewater degraded soil and its subsequent accumulation in sunflower tissues. The studied biochars including rice straw (RS), wheat straw (WS), acacia (AC) and sugarcane bagasse (SB) to wastewater irrigated soil containing Cd. Sunflower plant was grown as a test plant and Cd accumulation was recorded in its tissues, antioxidant enzymatic activity chlorophyll contents, plant biomass, yield and soil properties (pH, NPK, OM and Soluble Cd) were also examined. Results revealed that addition of biochar significantly minimized Cd mobility in soil by 53.4%, 44%, 41% and 36% when RS, WS, AC and SB were added at 2% over control. Comparing the control soil, biochar amended soil effectively reduced Cd uptake via plants shoots by 71.7%, 60.6%, 59% and 36.6%, when RS, WS, AC and SB. Among all the biochar, rice husk induced biochar significantly reduced oxidative stress and reduced SOD, POD and CAT activity by 49%, 40.5% and 46.5% respectively over control. In addition, NPK were significantly increased among all the added biochars in soil–plant system as well as improved chlorophyll contents relative to non-bioachar amended soil. Thus, among all the amendments, rice husk and wheat straw biochar performed well and might be considered the suitable approach for sunflower growth in polluted soil.     

The role of potassium phosphite in chlorophyll fluorescence and photosynthetic parameters of downy mildew-challenged cucumber Cucumis sativus plants

The effect of potassium phosphite (KPhi) on the photosynthetic parameters of cucumber plants inoculated with Pseudoperonospora cubensis was investigated in the present study. Cucumber plants were treated with KPhi before or after inoculation with P. cubensis and leaf samples were collected at different time courses for assessments. Results showed that in pathogen-inoculated plants Fv/Fm was decreased up to 3%. The rate of quantum photosynthetic was also decreased significantly in inoculated plants. Downy mildew led to a decrease in chlorophyll amount which in turn reduced the efficiency of photosystem II. In the KPhi-treated leaves, chlorophyll a and b decreased by 72% and 68%, respectively. Remarkable reduction in the efficiency of photosystem II as well as increased lipid membrane disruption, led to increased lipid peroxidation rate of the membranes up to 52%. The results of this study indicate the mitigating role of potassium phosphite in reducing the adverse effects of pathogen and maintaining the photosynthetic apparatus efficiency in cucumber plants.     

Pattern of cadmium accumulation and essential cations during growth of cadmium-tolerant fungi

The present study evaluates the growth response of two strains of filamentous fungi; a Fusarium sp. and Alternaria tenuis, grown on both solid and liquid Czapek Dox medium amended with different concentrations of CdCl₂. Colony extension and the mycelial dry weight of both fungi were significantly inhibited by high concentrations of cadmium. Extended lag phases and low growth rates resulted from cadmium administration. Cadmium drastically affected fungal morphogenesis by the production of stunted sterile thick mycelial filaments of the Fusarium sp. and chains of uncharacterized swellings instead of conidia in A. tenuis. Experiments showed that cadmium accumulation by the Fusarium sp. grown in liquid medium was a concentration dependent, and over the incubation time it displayed a plateau pattern. The cells grown on medium containing 0.25 mmol l^–1 CdCl₂ accumulated up to 89 ± 12 mol Cd (gm dw)^–1 after two days, falling to 29 ± 10 mol Cd (gm dw)^–1 after five days. At 0.5 mmol l^–1 CdCl₂ treatment the maximum cellular cadmium content was 132 ± 14 mol (gm dw)^–1, attained after 3 days, and decreased to 98 ± 9 mol (gm dw)^–1 at the end of the incubation time. There was a simultaneous marked drop in cadmium content and pH of the growth medium during the first few days. The presence of cadmium markedly altered the cellular essential cations; K⁺ and Mg²⁺ being decreased while Na⁺ increased during the growth period. Such findings resulted a reverse pattern of cellular Na⁺/K⁺ ratio for cells grown on cadmium-containing medium in respect to the control treatment. The results are discussed in relation to a further dimension of cadmium effects that might reflect its toxicity, as well as the implication of cadmium extrusion for tolerance during fungal growth.     

Effect of nitric oxide and putrescine on antioxidative responses under NaCl stress in chickpea plants

Chickpea plants were subjected to salt stress for 48 h with 100 mM NaCl, after 50 days of growth. Other batches of plants were simultaneously treated with 0.2 mM sodium nitroprusside (NO donor) or 0.5 mM putrescine (polyamine) to examine their antioxidant effects. Sodium chloride stress adversely affected the relative water content (RWC), electrolyte leakage and lipid peroxidation in leaves. Sodium nitroprusside and putrescine could completely ameliorate the toxic effects of salt stress on electrolyte leakage and lipid peroxidation and partially on RWC. No significant decline in chlorophyll content under salt stress as well as with other treatments was observed. Sodium chloride stress activated the antioxidant defense system by increasing the activities of peroxidase (POX), catalase (CAT) superoxide dismutase (SOD) and ascorbate peroxidase (APX). However no significant effect was observed on glutathione reductase (GR) and dehydro ascorbate reductase (DHAR) activities. Both putrescine and NO had a positive effect on antioxidant enzymes under salt stress. Putrescine was more effective in scavenging superoxide radical as it increased the SOD activity under salt stress whereas nitric oxide was effective in hydrolyzing H₂O₂ by increasing the activities of CAT, POX and APX under salt stress.     

Selenium modulates the activities of antioxidant enzymes,osmotic homeostasis and promotes the growth of sorrel seedlings under salt stress

Using physiological assays coupled with ultrathin tissue sections, we investigated the impacts of exogenous selenium (Se) on the growth, antioxidant enzymes, osmotic regulation and ultrastructural modifications of leaf mesophyll and root tip cells of 100 mM NaCl-stressed sorrel (Rumex patientia × R. tianshanicus) seedlings. At low concentrations (1–5 M), Se tended to stimulate the growth, the activities of superoxide dismutase and peroxidase enzymes, as well as the accumulation of water-soluble sugar in leaves of sorrel seedlings. At higher concentrations (10–30 M), Se exerted diminished beneficial effects on growth and enzyme activities. CAT activity did not change with Se addition (1–30 M). Electrolyte leakage of leaf cells declined, and K⁺ and Na⁺ ions increased in leaves with Se treatment, notably at 5 M of Se. TEM observations revealed that treatment with 5 M of Se positively promoted the integrity of membrane systems and cellular organelles, such as chloroplasts and mitochondria in leaf mesophyll and root tip cells. These results strongly suggest that an appropriate concentration of exogenous Se functions positively to promote the antioxidative and osmoregulatory capacity, and enhance the salt-resistance in sorrel seedlings.     

The effect of drought and ultraviolet radiation on growth and stress markers in pea and wheat

It emerged recently that there is an inter‐relationship between drought and ultraviolet‐B (UV‐B) radiation in plant responses, in that both stresses provoke an oxidative burst. The purpose of this investigation was to compare the effects and interaction of drought and UV‐B in wheat and pea. The absence of changes in relative leaf water content (RWC) after UV‐B treatments indicate that changes in water content were not involved. RWC was the main factor resulting in reduced growth in response to drought. Increases in anthocyanin and phenols were detected after exposure to UV‐B. The increases do not appear to be of sufficient magnitude to act as a UV‐B screen. UV‐B application caused greater membrane damage than drought stress, as assessed by lipid peroxidation as well as osmolyte leakage. An increase in the specific activities of antioxidant enzymes was measured after UV‐B alone as well as after application to droughted plants. Proline increased primarily in drought‐stressed pea or wheat. Proline may be the drought‐induced factor which has a protective role in response to UV‐B. The physiological and biochemical parameters measured indicate the UV‐B light has stronger stress effectors than drought on the growth of seedlings of both species. The two environmental stresses acted synergistically to induce protective mechanisms in that pre‐application of either stress reduced the damage caused by subsequent application of the other stress.     

Cadmium accumulation and its effects on physiological and biochemical characters of summer savory (Satureja hortensis L.).

Abstract

The objective of this study was to determine the effects of cadmium (Cd) toxicity on accumulation, growth, physiological responses, and biochemical characters in summer savory (Satureja hortensis L.). Plants were subjected to different levels of Cd concentrations including 0 (control), 2.5, 5, and 15?mg L^?1 in the growing medium. Cd exposure led to a significant increase in root and shoot Cd content. Calculation of bioaccumulation factor, translocation factor, and transfer coefficient revealed that Cd mostly accumulated in roots of S. hortensis and root to shoot transport was effectively restricted. Cd toxicity negatively affected plant growth and significantly reduced chlorophyll content. Contrarily, proline, soluble and reducing carbohydrates, anthocyanin content, and the activity of antioxidant enzymes significantly increased as a result of Cd exposure. Cd application led to a significant increase in essential oil content of S. hortensis. GC-MS analysis revealed that percentage main constitute of S. hortensi, carvacrol, which determines the quality of oil increased under the highest Cd treatment. Based on our findings, S. hortensis can be considered an invaluable alternative crop for mildly Cd-contaminated soils. Besides, due to the high potential of Cd accumulation in the root, S. hortensis may offer a feasible tool for phytostabilization purposes.