Brassica Water Extract Hormesis Improved Drought Tolerance and Antioxidative Defense in Wheat

Drought is one of the major environmental constraints, affecting agricultural productivity worldwide. Allelopathic hormesis, low dose stimulatory effect of allelochemicals, offers a pragmatic solution in alleviating the adverse effects of drought stress in plants. This study, therefore, was conducted to evaluate the potential of brassica water extract in enhancing drought tolerance in wheat. The experiment was comprised on three factors viz. drought with three levels (100%, 60% and 30% field capacity; FC), different concentrations of brassica water extract (control, water priming, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0%) and two wheat cultivars, Ihsan-2016 (drought-tolerant) and Galaxy-2013 (drought-sensitive). Drought stress, particularly at 30% FC decreased the morpho-physiological attributes of both wheat cultivars; nevertheless, the seed priming with brassica water extract at 1.5% effectively enhanced tolerance against drought stress. Compared with control, seed priming with 1.5% brassica water extract increased the morphological attributes such as seedling length, their fresh and dry weights of both wheat cultivars in the range of 29-142% under 30% field capacity. Besides, 1.5% brassica water extract triggered the activities of antioxidant enzymes including superoxide dismutase, catalase and peroxidase (28-150%), decreased the hydrogen peroxide contents (5-71%) and enhanced chlorophyll a, b, and carotenoid contents (57-201%) as compared to control in both wheat cultivars under 30% field capacity. Vigorous growth and higher drought tolerance in wheat-cultivars under brassica water extract priming were related to improved chlorophyll contents, physiological attributes, better antioxidant defense system, and reduced H2O2 based damaging effect.