Abstract
Effects of salinity caused by 150 mM NaCl on primary photochemical reactions and some physiological and biochemical parameters (K+/Na+ ratio, soluble sugars, proline, MDA) have been studied in five Triticum aestivum L. genotypes with contrasting salt tolerance. It was found that 150 mM NaCl significantly decreased the photosynthetic efficiency of two sensitive genotypes. The K+/Na+ ratio decreased in all genotypes exposed to salinity stress when compared with the control. Salinity stress also caused lipid peroxidation and accumulation of soluble sugars and proline. The amounts of soluble sugars and proline were higher in tolerant genotypes than sensitive ones, and lipid peroxidation was higher in sensitive genotypes. The noninvasive measurements of photosynthesis-related parameters indicated the genotype-dependent effects of salinity stress on the photosynthetic apparatus. The significant decrease of chlorophyll content (SPAD values) or adverse effects on photosynthetic functions at the PSII level (measured by the chlorophyll fluorescence parameters) were observed in the two sensitive genotypes only. Although the information obtained by different fast noninvasive techniques were consistent, the correlation analyses identified the highest correlation of the noninvasive records with MDA, K+/Na+ ratio, and free proline content. The lower correlation levels were found for chlorophyll content (SPAD) and Fv/Fm values derived from chlorophyll fluorescence. Performance index (PIabs) derived from fast fluorescence kinetics, and F735/F685 ratio correlated well with MDA and Na+ content. The most promising were the results of linear electron flow measured by MultispeQ sensor, in which we found a highly significant correlation with all parameters assessed. Moreover, the noninvasive simultaneous measurements of chlorophyll fluorescence and electrochromic band shift using this sensor indicated the apparent proton leakage at the thylakoid membranes resulting in a high proton conductivity (gH+), present in sensitive genotypes only. The possible consequences for the photosynthetic functions and the photoprotection are discussed.
Highlights
Being one of the extreme factors of the environment, soil salinity greatly impacts the development and productivity of agricultural plants (Arif et al 2019; Rastogi et al 2020)
The highest value of the K +/Na+ ratio in stress-exposed plants was recorded in the Mirbashir 128 (MIR), GOB genotypes, and the lowest value was recorded in the FAT and Zirva 80 (ZIR) genotypes (Fig. 1C)
The genotypic differences in expression of the genes responsible for individual protective mechanisms responsible for observed differences among the genotypes were not assessed in this study, the analytical parameters applied in this study provided a set of representative indicators covering multiple salt stress effects as well as mechanisms of tolerance at the different level, enabling to identify a high diversity of the responses in the set of tested genotypes, which could be efficiently compared with the results of the noninvasive indicators
Summary
Being one of the extreme factors of the environment, soil salinity greatly impacts the development and productivity of agricultural plants (Arif et al 2019; Rastogi et al 2020). Ionic, and oxidative stresses leads to plant death (Munns et al 2006; Sharma et al 2012; Zeeshan et al 2020). Salt stress leads to oxidative stress caused by the formation of reactive oxygen species (ROS). In this case, changes in various components of the cell such as lipid peroxidation, reduced enzymatic activities, oxidation of proteins, and damage to DNA occur (Jena 2012; Gupta and Huang 2014; Isayenkov and Maathuis 2019; Rasel et al 2020)
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