Alteration in morpho-physiological attributes of Leymus chinensis (Trin.) Tzvelev by exogenous application of brassinolide under varying levels of drought stress

Climate change and prolong drought adversely affect the grassland ecosystem, is precarious environmental constraint restricting plant growth and productivity. An experiment was conducted to alleviate adverse impacts of drought on physiochemical and morphological attributes of Leymus chinensis (Trin.) Tzvelev using brassinosteroid (BR). Treatments comprised well watered control (soil water contents 80%-85%) including Control (T0) and Control+ BR (TB0), moderate drought stress (soil water contents 50%-55%) including (T1) and T1+ BR (TB1) and severe drought stress (soil water contents 30%-35%) including (T2) and T2+ BR (TB2), they were laid out in completely randomized design with five replicates. Drought stress significantly impaired growth, osmotic substances, photosynthetic rate, and other physiochemical process. Moreover, perturbation in recorded attributes was aggravated by increasing drought severity from moderate to severe. Nevertheless, BR application (0.1 mg L-1) improved plant weight (38.8%-46.2%), relative water content (23.4%-29.1%), chlorophyll a (16.6%-56.5%), chlorophyll b (8.5%-16.9%), carotenoids (29.1%-67.3%), soluble sugars (1.7%-29.4%), free amino acids (15.4%-19.4%), and proline content (45.2%-79.4%); while, lowered malondialdehyde (34.8%-45.4%) at each level of drought. Likewise, BR application enhanced net photosynthetic rate (69.8%-165.1%), transpiration rate (45.0%-146.9%), water utilization efficiency (9.3%-16.0%), carboxylation utilization efficiency (80%-250%), sunlight utilization efficiency (66.6%-158.8%) and improved chlorophyll fluorescence characteristics at each level of drought, as compared to untreated controls. The adverse implications on physiochemical and morphological attributes were aggravated with the enhancing severity of drought from control to severe drought. Yet, 0.1 mg L-1 exogenous BR improved morphological and physiochemical attributes remarkably over respective controls and hence can be used to improve growth of drought stressed L. chinensis.