Search

A hydroponic experiment was conducted to observe the effects of various cadmium (Cd) levels (0, 50, 100 µM) on morphology and biochemical responses of nine different rice varieties. Initially, seeds were sown in sand in plastic pots. After 16 days of sowing, uniform seedlings were transferred to hydroponic set-up containing Hoagland solution and continuous aeration was provided with aeration pump. After six days, plants were applied the Cd stress for four weeks, then plants were harvested. Plants growth, biomass, photosynthesis, oxidative stress markers contents, antioxidant enzymes activities and Cd uptake in both root and shoot were measured. Results revealed that Cd negatively affected the plant growth as well as photosynthesis; while, oxidative stress and Cd uptake was increased with increasing Cd stress in all nine rice varieties. From this study, it was found that among all nine rice varieties, the Chenab variety was found most tolerant; while, the Kisan Basmati was found most sensitive variety against Cd stress. However, future studies are needed in order to investigate the detailed mechanism of Cd in different varieties of rice. [ABSTRACT FROM AUTHOR]

• Cadmium (Cd) stress reduced plant growth, generates oxidative stress and activates antioxidant defense system. • Application of Silicon (Si) enhanced plant growth and mitigates the oxidative stress induced by Cd. • Si supplementation enhanced endogenous nitric oxide (NO) and hydrogen sulphide (H 2 S) that helps in Cd stress tolerance. • cPTIO (NO scavenger) and hypotuarine, HT (H 2 S scavenger) decreased the NO and H 2 S level and antioxidant defense system • Both NO and H 2 S played a great role in Si-induced Cd tolerance in pepper plants. The current research was aimed to observe the interactive role of silicon-generated hydrogen sulfide (H 2 S) and nitric oxide (NO) on tolerance of pepper (Capsicum annum L.) plants to cadmium (Cd). Thus, the pepper plants were subjected to control (no Cd) or cadmium stress with and without Si supplementation. Significant decreases were found in plant dry weights, water potential, PSII maximum efficiency, glutathione (GSH), total chlorophyll, relative water content, Ca2+ and K+ concentrations and ascorbate, but there was a significant increase in H 2 O 2 , MDA, electron leakage (EL), proline, key antioxidant enzymes' activities, and endogenous Cd, NO and H 2 S in the Cd-stressed plants. Silicon enhanced Cd tolerance of the pepper plants by lowering the leaf Cd concentration, oxidative stress, enhancing the antioxidant defence system, leaf Si content, photosynthetic traits and plant growth as well as the contents of NO, proline and H 2 S. Furthermore, foliar-applied NO scavenger, cPTIO, and that of H 2 S, hypotaurine (HT), significantly decreased the levels of H 2 S alone, but cPTIO effectively reduced the concentrations of NO and H 2 S accumulated by Si in the Cd-stressed plants. The positive effect of Si was eliminated by cPTIO, but not by HT, suggesting that both molecules were involved in Si-induced improvement in Cd tolerance of the pepper plants. [ABSTRACT FROM AUTHOR]

Soil amendments are known to promote several plant growth parameters. In many agro-ecosystems, water scarcity and drought induced phosphorus deficiency limits crop yield significantly. Considering the climate change scenario, drought and related stress factors will be even more severe endangering the global food security. Therefore, two parallel field trials were conducted to examine at what extent soil amendment of leonardite and humic acid would affect drought and phosphorus tolerance of maize. The treatments were: control (C: 100% A pan and 125 kg P ha−1), P deficiency (phosphorus stress (PS): 62.5 kg P ha−1), water deficit stress (water stress (WS): 67% A pan), and PS + WS (67% A pan and 62.5 kg P ha−1). Three organic amendments were (i) no amendment, (ii) 625 kg S + 750 kg leonardite ha−1 and (iii) 1250 kg S + 37.5 kg humic acid ha−1) tested on stress treatments. Drought and P deficiency reduced plant biomass, grain yield, chlorophyll content, Fv/Fm, RWC and antioxidant activity (superoxide dismutase, peroxidase, and catalase), but increased electrolyte leakage and leaf H2O2 in maize plants. The combined stress of drought and P deficiency decreased further related plant traits. Humic acid and leonardite enhanced leaf P and yield in maize plants under PS. A significant increase in related parameters was observed with humic acid and leonardite under WS. The largest increase in yield and plant traits in relation to humic acid and leonardite application was observed under combined stress situation. The use of sulfur-enriched amendments can be used effectively to maintain yield of maize crop in water limited calcareous soils. [ABSTRACT FROM AUTHOR]

Alpha-tocopherol (α-Toc) is a member of the vitamin E family and is lipid soluble. Its biosynthesis is by the reaction of isopentyl diphosphate and homogentisic acid in plastid membranes. The putative biochemical activities of tocopherols are linked with the formation of tocopherol quinone species, which subsequently undergo degradation and recycling within cells/tissues. α-Toc plays a key role in a variety of plant metabolic processes throughout the ontogeny of plants. It can maintain the integrity and fluidity of photosynthesizing membranes. It can also neutralize lipid peroxy radicals, consequently blocking lipid peroxidation by quenching oxidative cations. It preserves membrane integrity by retaining membranous structural components under environmental constraints such as water deficiency, high salt content, toxic metals, high/low temperatures, and radiations. α-Toc also induces cellular signalling pathways within biological membranes. Its biosynthesis varies during growth and developmental stages as well as under different environmental conditions. The current review primarily focuses on how α-Toc can regulate various metabolic processes involved in promoting plant growth and development under stress and non-stress and how it can effectively counteract the stress-induced high accumulation of reactive oxygen species (ROS). Currently, exogenous application of α-Toc has been widely reported as a potential means of promoting resistance in plants to a variety of stressful environments. [ABSTRACT FROM AUTHOR]

Vitamins are regarded as vital growth substances. They act as cofactors of various key enzymes involved in metabolism and also have vital influence on metabolic activities of plants. They are believed to play a significant role in plants against abiotic stresses, particularly during water stress. The current experiment was conducted to evaluate the role of exogenously applied thiamin on two white clover cultivars, Super Late Fsd and Layalpur Late, at varying [100% (control), 80%, and 60% field capacities] water regimes. A significant suppression was noted in plant biomass, plant height, chlorophyll a and b contents, total soluble proteins, and shoot and root P, Ca2+, and K+ contents particularly at 60% field capacity in both cultivars. Drought stress had no significant effect on phenolic contents, but MDA concentration was increased in white clover cultivar Layalpur Late at both 80% and 60% drought levels. However, in Super Late Fsd, it was increased at 80% and decreased at 60% field capacity. Drought stress significantly enhanced levels/activities of ascorbic acid and antioxidant enzymes (CAT, SOD, and POD). Foliar spray of 50 mM thiamin improved the shoot and root fresh weights and shoot dry weight. Varying levels of thiamin were found significantly effective for shoot length, root length, and photosynthetic pigments (chlorophyll a and b). However, no considerable change was observed in ascorbic acid, total soluble proteins, and activities of antioxidants (SOD, CAT, and POD) due to exogenous spray of thiamin on two white clover cultivars. Of the two white clover cultivars, Super Late Fsd was better in shoot and root P and Layalpur Late in root dry weight and root length. Overall, 100 mM of thiamin was found effective in improving growth of both white clover cultivars, which can be attributed to thiamin-induced improvement in photosynthetic pigments and phenolic contents. [ABSTRACT FROM AUTHOR]

Chromium (Cr) is among the most toxic pollutants in the environment that adversely affect the living organisms and physiological processes in different plants. The present study investigated the effect of 15 mg L of 5-aminolevulinic acid (ALA) on morpho-physiological attributes of cauliflower ( Brassica oleracea botrytis L.) under different Cr concentrations (0, 10, 100, and 200 μM) in the growth medium. The results showed that Cr stress decreased the growth, biomass, photosynthetic, and gas exchange parameters. Chromium stress enhanced the activities of enzymatic antioxidants, catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) in response to oxidative stress caused by the elevated levels of malondialdehyde (MDA), hydrogen peroxide (HO), and electrolyte leakage (EL) in both roots and leaves of cauliflower. Chromium concentrations and total Cr uptake were increased in leaves, stems, and roots with increasing Cr levels in the culture medium. Foliar application of ALA increased the plant growth parameters, biomass, gas exchange parameters, and photosynthetic pigments under Cr stress compared to the treatments without ALA. Foliar application ALA decreased the levels of MDA, EL, and HO while further improved the performance of antioxidant in both leaves and roots compared to only Cr-stressed plant. Chromium concentrations and total Cr uptake were decreased by the ALA application compared to treatments without ALA application. The results of the present study indicated that foliar application of ALA might be beneficial in minimizing Cr uptake and its toxic effects in cauliflower. [ABSTRACT FROM AUTHOR]

In this study, changes in growth, chlorophyll pigments, proline, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents, and antioxidative enzyme activities were investigated in the seedlings of four different cultivars (cvs) of mustard [Brassica juncea (L.) Czern. & Coss.], i.e. Varuna, RH-30, Rohini, and Vaibhave under potassium (K) nutrition-deficient conditions. K deficiency induced a significant decrease in concentrations of photosynthetic pigments in all four cvs, however, this decrease was higher in cvs. Varuna and RH-30. During K deficiency, proline concentration increased in all mustard cvs, but a maximum increase in this parameter was shown by cvs. Varuna and RH-30. The activity of the key proline metabolizing enzyme γ-glutamyl kinase increased more in cvs. Varuna and RH-30 compared to cvs. Rohini and Vaibhave. The proline oxidase activity showed greater increase in cvs. Vaibhave and Rohini compared to cvs. Varuna and RH-30. K deficiency increased the concentrations of H2O2 and the activities of anti-oxidative defense system enzymes like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) in the seedlings of all mustard cvs, but higher activities of these enzymes were observed in cvs. Varuna and RH-30 compared to cvs. Rohini and Vaibhave. A significant lipid peroxidation in terms of MDA contents was also observed in the K-deficient seedlings of all four mustard cvs. This study suggests that K-starvation-induced oxidative stress through the high generation of reactive oxygen species (ROS). All mustard cvs counteracted to some extent the effects of ROS by activation of antioxidant machinery. Overall, the results indicate that of all four mustard cvs, Varuna and RH-30 were tolerant to K deficiency. [ABSTRACT FROM AUTHOR]

Exogenous application of different plant growth regulators is a well-recognized strategy to alleviate stress-induced adverse effects on different crop plants by regulating a variety of physiobiochemical processes such as photosynthesis, chlorophyll biosynthesis, nutrient uptake, antioxidant metabolism, and protein synthesis, which are directly or indirectly involved in the mechanism of stress tolerance. Of various environmental factors, salinity, drought, and extreme temperature (low or high) considerably diminish plant growth and yield by modulating endogenous levels as well as signaling pathways of plant hormones. Of various plant hormones/regulators, a potential plant growth regulator, 5-aminolevulinic acid (ALA), is known to be effective in counteracting the injurious effects of various abiotic stresses in plants. Until now the mechanisms behind ALA regulation of growth under stress have not been fully elucidated. It is also not yet clear how far growth and yield in different crops can be promoted by exogenous application of ALA and whether this ALA-induced growth and yield promotion is cost-effective. Thus, in this review we discuss at length the effects of ALA in regulating growth and development in plants under a variety of abiotic stress conditions, including salinity, drought, and temperature stress. Furthermore, advances in the functional and regulatory interactions of this plant growth regulator with plant stress tolerance, as well as the effective mode of exogenous application of ALA in inducing stress tolerance in plants are also comprehensively discussed in this review. In the future, overaccumulation of ALA in plants through manipulation of gene(s) could enhance plant stress tolerance. Thus, genetic manipulation of plants with the goal of attaining increased synthesis/accumulation of ALA and hence improved stress tolerance under stress conditions is an important area for research. [ABSTRACT FROM AUTHOR]

• To assess foliar applied L-methionine (Met) could improve drought tolerance in bitter gourd. • Exogenous application of Met was found to be beneficial in improving plant growth and modulating some of the important biochemical parameters involved in drought tolerance. • Bitter gourd cultivar Ruyu-53 was relatively better in proline, total phenolics and petiole abaxial epidermis thickness. Methionine is an important sulfur-containing amino acid and it plays a central role for several diverse purposes in the living organisms. This study was arranged to determine the effect of foliage application of 10 and 20 mg/L of L-methionine to analyze various physio-biochemical attributes and different anatomical features of bitter gourd (Momordica charantia L.) under control and drought stress conditions. Water deficit conditions (60 % field capacity) adversely reduced shoot fresh and dry weights, root fresh weight, shoot length, leaf xylem area, leaf phloem area, petiole adaxial epidermis thickness, petiole xylem area, petiole phloem area, and petiole cortical cell area. While a considerable elevation was found in total phenolics, glycine betaine, leaf adaxial and abaxial epidermal thickness, leaf vascular bundle area, petiole adaxial epidermal cell area and petiole vascular bundle area. The foliar application of L-methionine increased the shoot and root fresh weights, shoot length, total phenolics, ascorbic acid, glycine betaine, leaf abaxial epidermal thickness, leaf adaxial epidermal cell area, leaf abaxial epidermal cell area, leaf vascular bundle area, leaf xylem area and leaf phloem area. The application of 10 mg/L L-methionine was found to be comparatively more effective for regulating the levels of hydrogen peroxide, leaf abaxial epidermal thickness, leaf abaxial epidermal cell area, leaf xylem area, petiole abaxial epidermal thickness, whereas 20 mg/L concentration was effective for improving shoot fresh weight, shoot dry weight, shoot and root lengths, chlorophyll a and glycine betaine contents. Overall, bitter gourd cultivar Ruyu-53 was relatively better in proline, total phenolics and petiole abaxial epidermis thickness, whereas cv. Ruyu-146 was better in accumulating ascorbic acid. [ABSTRACT FROM AUTHOR]

Abstract: Two eggplant cultivars, Dilnasheen and Bemisal, were selected to assess whether pure GB and sugarbeet extract could effectively ameliorate the harmful effects of salt stress on eggplant (Solanum melongena L.), under saline conditions. Salt stress markedly suppressed the growth, yield, photosynthetic capacity, internal CO2 level, transpiration, and stomatal conductance in both cultivars. Potassium (K+) and Ca2+ contents and K+/Na+ ratios of both root and leaf were also reduced, while GB and proline in leaves, and Na+ and Cl− contents in roots and leaves were significantly enhanced. Exogenously applied glycinebetaine and sugarbeet extracts significantly counteracted the salt-induced adverse effects on growth, yield, various gas exchange characteristics, GB and leaf K+, Ca+, Cl− and Na+. However, GB and sugarbeet extract showed differential effects on photosynthetic rate, stomatal conductance and transpiration, internal CO2 level, C i /C a ratio, leaf K+, Ca2+, and Cl− contents, and K+/Na+ ratio. Sugarbeet extract proved better than the GB in improving growth, photosynthetic rate, transpiration, stomatal conductance, yield and GB accumulation. Since, sugarbeet extract contains a substantial amount of GB along with a variety of other important nutrients so it was found as effective as pure GB in improving growth and some key physiological processes in eggplant under salt stress. Thus, it can be used as an alternative cheaper source of GB for its use as an ameliorative agent for protecting plants against the hazardous effects of salt stress. [Copyright &y& Elsevier]

Abstract: To assess whether foliar application of K+S as potassium sulfate (K2SO4) could alleviate the adverse effects of salt on sunflower (Helianthus annuus L. cv. SF-187) plants, a greenhouse experiment was conducted. There were two NaCl levels (0 and 150mM) applied to the growth medium and six levels of K+S as K2SO4 (NS (no spray), WS (spray of water+0.1% Tween 20 solution), 0.5% K+0.21% S, 1.0% K+0.41% S, 1.5% K+0.62% S, and 2.0% K+0.82% S in 0.1% Tween-20 solution) applied two times foliarly to non-stressed and salt-stressed sunflower plants. Salt stress markedly repressed the growth, yield, photosynthetic pigments, water relations and photosynthetic attributes, quantum yield (Fv/Fm ), leaf and root K+, Mg2+, P, Ca2+, N as well as K+/Na+ ratios, while it enhanced the cell membrane permeability, and leaf and root Na+ and Cl− concentrations. Foliar application of potassium sulfate significantly improved growth, achene yield, photosynthetic and transpiration rates, stomatal conductance, water use efficiency, leaf turgor and enhanced shoot and leaf K+ of the salt-stressed sunflower plants, but it did not improve leaf and root Na+, Cl−, Mg2+, P, Ca2+, N as well as K+/Na+ ratios. The most effective dose of K+S for improving growth and achene yield was found to be 1.5% K+0.62% S and 1% K+0.41% S, respectively. Improvement in growth of sunflower plants due to exogenously applied K2SO4 was found to be linked to enhanced photosynthetic capacity, water use efficiency, leaf turgor and relative water content. [Copyright &y& Elsevier]

Abstract: Ageing or senescence is an intricate and highly synchronized developmental phase in the life of plant parts including leaf. Senescence not only means death of a plant part, but during this process, different macromolecules undergo degradation and the resulting components are transported to other parts of the plant. During the period from when a leaf is young and green to the stage when it senesces, a multitude of factors such as hormones, environmental factors and senescence associated genes (SAGs) are involved. Plant hormones including salicylic acid, abscisic acid, jasmonic acid and ethylene advance leaf senescence, whereas others like cytokinins, gibberellins, and auxins delay this process. The environmental factors which generally affect plant development and growth, can hasten senescence, the examples being nutrient dearth, water stress, pathogen attack, radiations, high temperature and light intensity, waterlogging, and air, water or soil contamination. Other important influences include carbohydrate accumulation and high carbon/nitrogen level. To date, although several genes involved in this complex process have been identified, still not much information exists in the literature on the signalling mechanism of leaf senescence. Now, the Arabidopsis mutants have paved our way and opened new vistas to elucidate the signalling mechanism of leaf senescence for which various mutants are being utilized. Recent studies demonstrating the role of microRNAs in leaf senescence have reinforced our knowledge of this intricate process. This review provides a comprehensive and critical analysis of the information gained particularly on the roles of several plant growth regulators and microRNAs in regulation of leaf senescence. [Copyright &y& Elsevier]