Effect of nano-zinc oxide and drought stress on the activity of hydrolytic enzymes and seed reserves mobilization of soybean (Glycine max. L) cultivar Katul (DPX)

To evaluate the effect of drought stress originated from poly ethylene glycol and application of nano ZnO on the activity of hydrolytic enzymes and soybean seed reserves mobilization a factorial experiment was conducted based on completely randomized design with three replications at the University of Mohaghegh Ardabili in 2016. Treatments were drought stress at three levels as 0, -0.7 and -1.4 MPa and nano zinc oxide at the concentrations of 0, 0.75 and 1.5 g lit-1. Germination percentage and rate, seedling length and dry weight, activity of hydrolytic enzymes (alpha-amylase, protease and lipase) and seed reserves (carbohydrate, protein and lipid) mobilization were measured. Results showed that nano zinc oxide had the positive effect on germination percentage and rate, activity of hydrolytic enzymes and mobilization of carbohydrate, lipid and protein reserves. So that application of 1.5 g lit-1 of nano ZnO increased the activity of lipase, protease and α-amylase about 11.75, 12.75 and 11.87%, respectively in severe drought stress compared to non-stress condition. Drought stress also decreased the seed reserves mobilization in addition to reducing the activity of hydrolytic enzymes. There was a reduction trend in the mobilization of carbohydrates, lipids and proteins under drought stress with the increasing in imbibition time, while application of nano ZnO increased the mobilization of seed reserves which is the indicator of growth and production of higher seedling dry weight. Considering the ameliorative effect of nano ZnO on the damages due to drought stress and increasing the seed reserves using efficiency, activity of hydrolytic enzymes and germination percentage it seems that application of nano ZnO in the concentration of 1.5 g lit-1 will improve the soybean seed germination under drought conditions.