He–Ne Laser Priming Enhances Drought Tolerance in Wheat through Differential Modification of Photosynthetic Pigments and Antioxidative Enzymes

Water stress seriously impacts agro-systems worldwide, severely affecting plant growth and crop productivity. Radio-priming agents such as lasers can induce stress tolerance in plants due to their physiological roles in growth and development. The potential protective role of He–Ne laser pretreatment (i.e., one, two and five min at 630 nm) was evaluated in germination and growth of two wheat varieties, FSD-2008 and Anaj-2017, under water-stressed (50% field capacity) environments. Drought and laser priming significantly affected the growth (shoot and shoot fresh and dry weight and lengths), grain yield (number of total and fertile tillers and 100-grain weight), biochemical attributes (total soluble proteins and total free amino acids), and ionic concentration of both tested wheat varieties. In this study, the 2 min laser priming treatments were most effective for protecting wheat plants from drought stress. While the prolonged treatment duration significantly inhibited growth. We conclude that laser pretreatment assisted wheat plants in sustaining biomass assimilation, growth and yield formation by protecting their pigments and key metabolites from drought-induced oxidative injury. This study suggested that 2 min of laser priming had a much better result than other time duration, i.e., 1 and 5 min of laser priming.