No abstract

Increased activities of enzymatic and non-enzymatic antioxidants provide a common reaction to environmental stress in most crops. To investigate the effect of foliar application of stress moderators on enzymatic and non-enzymatic antioxidant changes, field experiments were conducted as split-plot design based on a randomized complete block design with three replications in 2017 and 2018. Planting date (early and late) was considered as the main plot, and foliar applications with 50 and 100 mM of Glycine Betaine, 1 and 2 mM of salicylic acid, and 100 and 200 lM of sodium nitroprusside, along with the control treatment, were regarded as the subplot. The results showed that the amounts of chlorophyll pigments and the levels of enzymatic antioxidants (glutathione peroxidase, ascorbate peroxidase, superoxide dismutase, catalase), and proline increased, and H 2 O 2 level decreased with the foliar application of stress moderators. Glycine betaine and sodium nitroprusside had the lowest and highest effects on the enzymatic antioxidant activities, respectively. The analysis of the main components revealed that in the early and delay planting date, the characteristics of enzymatic antioxidants and photosynthetic properties had the greatest effects on the enhancement of tolerance to salinity stress. In general, the results of this research demonstrated that the elevated activities of enzymatic antioxidants compared to non-enzymatic ones were more effective in reducing the impacts of salinity stress. Moreover, the foliar application of sodium nitroprusside at a concentration of 100 lM served as the most suitable moderator for augmenting the activities of enzymatic antioxidants in salinity stress conditions.

Background Today, stress moderators are employed to mitigate crop loss due to the adverse effects of environmental stress. The current research aimed to investigate the impacts of time and stress moderator types on agro-physiological responses of cotton on conventional and double-cropping systems during 2017 and 2018 under saline conditions. A split-plot factorial experiment was carried out in a randomized complete block design with three replications. Cultivation system [conventional (recommended planting date) and double-cropping systems (sowing after harvest of wheat)] were considered as the main plots, and stress moderator type at four levels [water control, 2 mmol·L–1 Salicylic acid (SA), 100 mmol·L–1 Glycine betaine (GB), and 100 μmol·L–1 sodium nitroprusside (SNP)] and application time (flowering and flowering + bolling stages) were regarded as subplots. Results Plant height, reproductive branch number, the number of bolls, 10-boll weight, 1 000-seed weight, biological yield, seed cotton yield, lint yield, chlorophyll a, chlorophyll b, carotenoids, total chlorophyll, sodium, potassium, and proline content were less in double-cropping system comparing with conventional system. Spraying with the stress moderators alleviated soil salinity effects on yield, yield components, and biochemical traits of cotton. SNP spraying led to maximum plant height, branch number, the number of bolls per plant, 10-boll weight and seed cotton yield. SA spraying yielded the highest 1 000-seed weight, biological yield, lint percentage and lint yield. The highest chlorophyll a, chlorophyll b, carotenoids, and total chlorophyll content resulted from SNP spraying. Yield, yield components, and biochemical traits did not respond to the stress moderator types in double-cropping system. However, the highest chlorophyll a, carotenoids, proline content, the number of bolls per plant, and seed cotton yield resulted from SNP spraying in conventional system. No statistically significant differences were observed between spraying with SNP and SA in most studied traits. Conclusions The results suggest that the optimum cotton planting time and SNP spraying could be recommended for producing the most suitable yield under saline conditions. Highlights External application of stress modulators increases salinity stress tolerance. Spraying with sodium nitroprusside has more moderating effect. Agro-physiological response of cotton to moderators is stronger in early sowing. Maximum seed cotton yield was achieved at early sowing and spraying sodium nitroprusside. Delayed cultivation reduces cotton yield.