Responses of leaf gas exchange attributes, photosynthetic pigments and antioxidant enzymes in NaCl-stressed cotton (Gossypium hirsutum L.) seedlings to exogenous glycine betaine and salicylic acid

Abstract

Background Application of exogenous glycine betaine (GB) and exogenous salicylic acid (SA) mitigates the adverse effects of salinity. Foliar spraying with exogenous GB or SA alleviates salt stress in plants by increasing leaf gas exchange and stimulating antioxidant enzyme activity. The effects of foliar application of exogenous GB and SA on the physiology and biochemistry of cotton seedlings subjected to salt stress remain unclear. Results Results showed that salt stress of 150 mM NaCl significantly reduced leaf gas exchange and chlorophyll fluorescence and decreased photosynthetic pigment quantities and leaf relative water content. Foliar spray concentrations of 5.0 mM exogenous GB and 1.0 mM exogenous SA promoted gas exchange and fluorescence in cotton seedlings, increased quantities of chlorophyll pigments, and stimulated the antioxidant enzyme activity. The foliar spray also increased leaf relative water content and endogenous GB and SA content in comparison with the salt-stressed only control. Despite the salt-induced increase in antioxidant enzyme content, exogenous GB and SA in experimental concentrations significantly increased the activity of glutathione reductase, ascorbate peroxidase, superoxide dismutase, catalase and peroxidase, and decreased malondialdehyde content under salt stress. Across all experimental foliar spray GB and SA concentrations, the photochemical efficiency of photosystem II (FV/FM) reached a peak at a concentration of 5.0 mM GB. The net photosynthetic rate (Pn) and FV/FM were positively correlated with chlorophyll a and chlorophyll b content in response to foliar spraying of exogenous GB and SA under salt stress. Conclusions We concluded, from our results, that concentrations of 5.0 mM GB or 1.0 mM SA are optimal choices for mitigating NaCl-induced damage in cotton seedlings because they promote leaf photosynthesis, increase quantities of photosynthetic pigments, and stimulate antioxidant enzyme activity. Among, 5.0 mM GB and 1.0 mM SA, the best performance in enhancing endogenous GB and SA concentrations was obtained with the foliar application of 1.0 mM SA under salt stress.

Application of Exogenous Protectants Mitigates Salt-Induced Na+ Toxicity and Sustains Cotton (Gossypium hirsutum L.) Seedling Growth: Comparison of Glycine Betaine and Salicylic Acid

“…In a previous study, we found exogenous foliar-applied GB significantly enhanced the endogenous accumulation of GB but had a non-significant effect on the accumulation of endogenous SA compared with changes under NaCl stress without supplementation. In contrast, the SA-containing foliar spray significantly stimulated both endogenous GB and SA accumulation [37]. In agreement with our observations, exogenously sprayed SA ameliorated the accumulation of endogenous GB in Vigna radiata subjected to salinity stress [19].…”

“…In a recent study, we observed that as a response to 150 mM NaCl stress, the endogenous biosynthesis of GB and SA was significantly increased compared with the wellwatered treatment control [37]. Our findings are in good agreement with those of Chen and Murata [38,39], who reported that plants synthesize GB under environmental stress, including salinity.…”

“…Similarly, Pál, et al [40] reported that SA is endogenously accumulated to protect plants against the negative impacts of abiotic stresses, including salinity and many others, and ensuring plant growth and development. However, despite a significant accumulation of GB and SA in cotton seedling leaves under NaCl stress, the seedlings were unable to mitigate the adverse effects caused by NaCl stress [37]. In a previous study, we found exogenous foliar-applied GB significantly enhanced the endogenous accumulation of GB but had a non-significant effect on the accumulation of endogenous SA compared with changes under NaCl stress without supplementation.…”

Resveratrol Alleviates the KCl Salinity Stress of Malus hupehensis Rhed

“…M. hupehensis is one of the most popular rootstocks for apple production and cultivation ( Su et al, 2020 ) but unfortunately suffers from serious KCl stress due to the huge amount of potassium fertilizer applied to orchards ( Zheng et al, 2021 ). Introducing exogenous substances such as plant growth regulator, osmotic adjustment substances, and antioxidants effectively alleviates salt stress ( Li et al, 2012 ; Chen et al, 2019 ; Hamani et al, 2020 ). As an antimicrobial phytoalexin, Res has an effect on high boron in pepper plants and alleviates NaCl stress in citrus seedlings ( Kostopoulou et al, 2014 ; Sarafi et al, 2017 ).…”

Resveratrol Alleviates the KCl Salinity Stress of Malus hupenensis Rhed. Seedlings by Regulating K+/Na+ Homeostasis, Osmotic Adjustment, and Reactive Oxygen Species Scavenging

“…M. hupehensis is one of the most popular rootstocks for apple production and cultivation [51], but unfortunately suffers from serious KCl stress due to the huge amount of potassium fertilizer applied to orchards. Introducing exogenous substances such as plant growth regulator, osmotic adjustment substances, and antioxidants effectively alleviates salt stress [52,53,54]. As an antimicrobial phytoalexin, Res alleviates NaCl stress in citrus seedlings [42].…”