Ethylene plays a crucial role throughout the life cycle of plants under optimal and stressful environments. The present study reports the involvement of exogenously sourced ethylene (as ethephon; ...2-chloroethyl phosphonic acid) in the protection of the photosynthetic activity from glucose (Glu) sensitivity through its influence on the antioxidant system for adaptation of wheat (Triticum aestivum L.) plants under salt stress. Ten-day-old plants were subjected to control and 100 mM NaCl and treated with 200 µl L
ethephon on foliage at 20 days after seed sowing individually or in combination with 6% Glu. Plants receiving ethylene exhibited higher growth and photosynthesis through reduced Glu sensitivity in the presence of salt stress. Moreover, ethylene-induced reduced glutathione (GSH) production resulted in increased psbA and psbB expression to protect PSII activity and photosynthesis under salt stress. The use of buthionine sulfoximine (BSO), GSH biosynthesis inhibitor, substantiated the involvement of ethylene-induced GSH in the reversal of Glu-mediated photosynthetic repression in salt-stressed plants. It was suggested that ethylene increased the utilization of Glu under salt stress through its influence on photosynthetic potential and sink strength and reduced the Glu-mediated repression of photosynthesis.
Heat stress adversely affects plants growth potential. Global warming is reported to increase in the intensity, frequency, and duration of heatwaves, eventually affecting ecology, agriculture and ...economy. With an expected increase in average temperature by 2–3 °C over the next 30–50 years, crop production is facing a severe threat to sub-optimum growth conditions. Abscisic acid (ABA) and nitric oxide (NO) are growth regulators that are involved in the adaptation to heat stress by affecting each other and changing the adaptation process. The interaction between these molecules has been discussed in various studies in general or under stress conditions; however, regarding high temperature, their interaction has little been worked out. In the present review, the focus is shifted on the role of these molecules under heat stress emphasizing the different possible interactions between ABA and NO as both regulate stomatal closure and other molecules including hydrogen peroxide (H
2
O
2
), hydrogen sulfide (H
2
S), antioxidants, proline, glycine betaine, calcium (Ca
2+
) and heat shock protein (HSP). Exploring the crosstalk between ABA and NO with other molecules under heat stress will provide us with a comprehensive knowledge of plants mechanism of heat tolerance which could be useful to develop heat stress-resistant varieties.
Drought has been highly prevalent around the world especially in Sub‐Saharan Africa and South‐East Asian countries. Consistent climatic instabilities and unpredictable rainfall patterns are further ...worsening the situation. Rice is a C3 staple cereal and an important food crop for the majority of the world's population and drought stress is one of the major growth retarding threats for rice that slashes down grain quality and yield. Drought deteriorates rice productivity and induces various acclimation responses that aids in stress mitigation. However, the complexity of traits associated with drought tolerance has made the understanding of drought stress‐induced responses in rice a challenging process. An integrative understanding based on physiological adaptations, omics, transgenic and molecular breeding approaches successively backed up to developing drought stress‐tolerant rice. The review represents a step forward to develop drought‐resilient rice plants by exploiting the knowledge that collaborates with omics‐based developments with integrative efforts to ensure the compilation of all the possible strategies undertaken to develop drought stress‐tolerant rice.
Salicylic acid (SA) is known to affect photosynthesis under normal conditions and induces tolerance in plants to biotic and abiotic stresses through influencing physiological processes. In this ...study, physiological processes were compared in salt-tolerant (Pusa Vishal) and salt-sensitive (T44) cultivars of mungbean and examined how much these processes were induced by SA treatment to alleviate decrease in photosynthesis under salt stress. Cultivar T44 accumulated higher leaf Na
+ and Cl
− content and exhibited greater oxidative stress than Pusa Vishal. Activity of antioxidant enzymes, ascorbate peroxidase (APX) and glutathione reductase (GR) was greater in Pusa Vishal than T44. Contrarily, activity of superoxide dismutase (SOD) was greater in T44. The greater accumulation of leaf nitrogen and sulfur through higher activity of their assimilating enzymes, nitrate reductase (NR) and ATP-sulfurylase (ATPS) increased reduced glutathione (GSH) content more conspicuously in Pusa Vishal than T44. Application of 0.5
mM SA increased nitrogen and sulfur assimilation, GSH content and activity of APX and GR. This resulted in the increase in photosynthesis under non-saline condition and alleviated the decrease in photosynthesis under salt stress. It also helped in restricting Na
+ and Cl
− content in leaf, and maintaining higher efficiency of PSII, photosynthetic N-use efficiency (NUE) and water relations in Pusa Vishal. However, application of 1.0
mM SA resulted in inhibitory effects. The effect of SA was more pronounced in Pusa Vishal than T44. These results indicate that SA application alleviates the salt-induced decrease in photosynthesis mainly through inducing the activity of NR and ATPS, and increasing antioxidant metabolism to a greater extent in Pusa Vishal than T44.
We investigated the potential of salicylic acid (SA) in alleviating the adverse effects of heat stress on photosynthesis in wheat (Triticum aestivum L.) cv WH 711. Activity of ribulose ...1,5-bisphosphate carboxylase (Rubisco), photosynthetic-nitrogen use efficiency (NUE), and net photosynthesis decreased in plants subjected to heat stress (40°C for 6 h), but proline metabolism increased. SA treatment (0.5 mM) alleviated heat stress by increasing proline production through the increase in γ-glutamyl kinase (GK) and decrease in proline oxidase (PROX) activity, resulting in promotion of osmotic potential and water potential necessary for maintaining photosynthetic activity. Together with this, SA treatment restricted the ethylene formation in heat-stressed plants to optimal range by inhibiting activity of 1-aminocyclopropane carboxylic acid (ACC) synthase (ACS). This resulted in improved proline metabolism, N assimilation and photosynthesis. The results suggest that SA interacts with proline metabolism and ethylene formation to alleviate the adverse effects of heat stress on photosynthesis in wheat.
The effect of exogenously-applied ethylene sourced from ethephon (2-chloroethyl phosphonic acid)was studied on photosynthesis, carbohydrate metabolism, and high-temperature stress tolerance in ...Taipei-309 and Rasi cultivars of rice (
L.). Heat stress increased the content of H
O
and thiobarbituric acid reactive substances (TBARS)more in Rasi than Taipei-309. Further, a significant decline in sucrose, starch, and carbohydrate metabolism enzyme activity and photosynthesis was also observed in response to heat stress. The application of ethephon reduced H
O
and TBARS content by enhancing the enzymatic antioxidant defense system and improved carbohydrate metabolism, photosynthesis, and growth more conspicuously in Taipei-309 under heat stress. The ethephon application enhanced photosynthesis by up-regulating the
and
genes of photosystem II in heat-stressed plants. Interestingly, foliar application of ethephoneffectively down-regulated high-temperature-stress-induced elevated ethylene biosynthesis gene expression. Overall, ethephon application optimized ethylene levels under high-temperature stress to regulate the antioxidant enzymatic system and carbohydrate metabolism, reducing the adverse effects on photosynthesis. These findings suggest that ethylene regulates photosynthesis via carbohydrate metabolism and the antioxidant system, thereby influencing high-temperature stress tolerance in rice.
The involvement of nitric oxide (NO) and hydrogen sulfide (H
S) in countermanding heat-inhibited photosynthetic features were studied in wheat (
L.). Heat stress (HS) was employed at 40 °C after ...establishment for 6 h daily, and then plants were allowed to recover at 25 °C and grown for 30 days. Glucose (Glc) content increased under HS and repressed plant photosynthetic ability, but the application of sodium nitroprusside (SNP, as NO donor) either alone or with sodium hydrosulfide (NaHS, as H
S donor) reduced Glc-mediated photosynthetic suppression by enhancing ascorbate-glutathione (AsA-GSH) metabolism and antioxidant system, which reduced oxidative stress with decreased H
O
and TBARS content. Oxidative stress reduction or inhibiting Glc repression was maximum with combined SNP and NaHS treatment, which was substantiated by 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) and hypotaurine (HT), scavengers for NO and H
S, respectively. The scavenge of H
S reduced NO-mediated alleviation of HS suggesting of its downstream action in NO-mediated heat-tolerance. However, a simultaneous decrease of both (NO and H
S) led to higher Glc-mediated repression of photosynthesis and oxidative stress in terms of increased H
O
content that was comparable to HS plants. Thus, NO and H
S cooperate to enhance photosynthesis under HS by reducing H
O
-induced oxidative stress and excess Glc-mediated photosynthetic suppression.
Salicylic acid (SA) is a well-known plant growth regulator, which participates in many physiological processes of plants under normal and stressful conditions. In this study, we investigated the ...impact of SA supplementation on the components of ascorbate-glutathione cycle and glyoxalase system, photosynthesis and growth of rice (Oryza sativa) plants subjected to arsenic (As) stress. Plants grown with As exhibited enhanced As uptake, increased oxidative stress, and photosynthesis and growth inhibition. Application of SA promoted photosynthesis and growth in plants with or without As stress by improving plant defense systems and reducing oxidative stress through interaction with ethylene and nitric oxide (NO). SA acted as an ethylene antagonist, reducing stress ethylene formation under As stress, while NO formation was induced. This resulted in coordinated control over the antioxidant defense systems and enhanced As tolerance, protecting photosynthesis and growth from As-induced damage. The study showed that positive responses of SA in promoting photosynthesis and growth under As stress were the result of its interplay with ethylene and NO, enhanced capacity of defense systems to reduce oxidative stress. The crosstalk of SA with ethylene and NO will be useful in augmenting the performance of rice plants under As stress.
•Arsenic stress increases oxidative stress and inhibits photosynthesis.•Salicylic acid strengthens defense mechanisms under As stress.•Salicylic acid improves photosynthesis and growth under As stress.•Salicylic acid interacts with ethylene and nitric oxide for As tolerance.
The severity of salt stress is alarming for crop growth and production and it threatens food security. Strategies employed for the reduction in stress are not always eco-friendly or sustainable. ...Plant-growth-promoting rhizobacteria (PGPR) could provide an alternative sustainable stress reduction strategy owning to its role in various metabolic processes. In this study, we have used two strains of PGPR,
(NAIMCC-B-00340) and
Beijerinck 1901 (MCC 2351), either singly or in combination, and studied their effect in the amelioration of salt toxicity in mustard cultivar Pusa Jagannath via its influence on plants' antioxidants' metabolism, photosynthesis and growth. Individually, the impact of
was better in reducing stress ethylene, oxidative stress, photosynthesis and growth but maximal alleviation was observed with their combined application. MDA and H
O
content as indicator of oxidative stress decreased by 27.86% and 45.18% and osmolytes content (proline and glycine-betaine) increased by 38.8% and 26.3%, respectively, while antioxidative enzymes (SOD, CAT, APX and GR) increased by 58.40, 25.65, 81.081 and 55.914%, respectively, over salt-treated plants through the application of
. The combined application maximally resulted in more cell viability and less damage to the leaf with lesser superoxide generation due to higher antioxidative enzymes and reduced glutathione formation (GSH). Considering the obtained results, we can supplement the PGPR in combination to plants subjected to salt stress, prevent photosynthetic and growth reduction, and increase the yield of plants.
Sulfur (S) assimilation results in the synthesis of cysteine (Cys), a common metabolite for the formation of both reduced glutathione (GSH) and ethylene. Thus, ethylene may have regulatory ...interaction with GSH in the alleviation of salt stress. The involvement of ethylene in the alleviation of salt stress by S application was studied in mustard (Brassica juncea cv. Pusa Jai Kisan). First, the effects of 0, 0.5, 1.0 and 2.0 mM SO₄ ² ⁻ were studied on photosynthetic and growth parameters to ascertain the S requirement as sufficient‐S and excess‐S for the plant. In further experiments, the effects of sufficient‐S (1 mM SO₄ ² ⁻) and excess‐S (2 mM SO₄ ² ⁻) were studied on the alleviation of salt stress‐induced by 100 mM NaCl, and ethylene involvement in the alleviation of salt stress by S. Under non‐saline condition, excess‐S increased ethylene with less content of Cys and GSH and adversely affected photosynthesis and growth. In contrast, excess‐S maximally alleviated salt stress due to high demand for S and optimal ethylene formation, which maximally increased GSH and promoted photosynthesis and growth. The involvement of ethylene in S‐mediated alleviation of salt stress was further substantiated by the reversal of the effects of excess‐S on photosynthesis by aminoethoxyvinylglycine (AVG), ethylene biosynthesis inhibitor. The studies suggest that plants respond differentially to the S availability under non‐saline and salt stress and excess‐S was more potential in the alleviation of salt stress. Further, ethylene regulates plants' response and excess S‐induced alleviation of salt stress and promotion of photosynthesis.
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