Foliar Melatonin Application Mitigates Salt Stress Effects on Wheat Photosynthesis, Antioxidant Activity and Grain Quality

Abstract

The present study was performed at the Farm of the Department of Laboratory, China. To evaluate the effects of pre-anthesis melatonin priming in alleviating the negative impact of post-anthesis salt stress on plant growth, yield, and quality of two winter wheat (Triticum aestivum L.), Yangmai 16 from China and Imam from Sudan. Pre-anthesis wheat plants at nine-leaf-stage were separately treated with 500 μM of melatonin and after post-anthesis consequently exposed to 100 and 300 mM of NaCl. Five concentrations were used: CT: Control; S1: 100 mM NaCl only; S2: 300 mM NaCl only; S1+M: 100 mM NaCl +melatonin, S2+M: 300 mM NaCl + melatonin. The treatments were arranged in a Randomized Complete Block Design (RCBD) with four replications. Parameters measured under study were analyzed statistically using SPSS (SPSS Inc, Chicago, IL). Significantly different means of the measured data separated at the 0.05 probability level using Duncan’s Multiple Range Test (DMRT). The results demonstrated that post-anthesis salt stress led to a significant decrease in plant height, flag leaf area, fresh and dry weight of shoot and root, relative water content (RWC), while the pre-anthesis foliar application of melatonin alleviated these declines. Also, post-anthesis salt stress decreased chlorophyll, indole acetic acid (IAA), gas exchange and Chlorophyll fluorescence parameters contents, antioxidant activities, yield and yield components’ characters, protein and starch concentration, Ca+2 and K+ contents, but pre-anthesis with 500 μM of foliar melatonin application improved these parameters. We also found that post-anthesis salt- stressed plants had elevated reactive oxygen species (ROS) malondialdehyde (MDA), hydrogen peroxide (H2O2) contents, superoxide (O2-), sodium (Na+) contents, where pre- anthesis treated with melatonin lowered these parameters. Then, pre- anthesis treatment with 500 μM of foliar melatonin expected to be a best alternative to mitigate the negative effects of post-anthesis salts stress at plant growth yield and yield components and grain quality in wheat.