Thiourea-induced metabolic changes in two mung bean [Vigna radiata (L.) Wilczek] (Fabaceae) varieties under salt stress

A pot experiment was conducted to assess the effect of foliar application of thiourea on two mung bean (Vigna radiata (L.) Wilczek) varieties (NM-2006 and NM-2011) under salt stress. Experiment was laid-out in a completely randomized design with four replicates. Two salt treatments [non-saline (control) and 75 mM NaCl] were applied to 28-day-old mung bean plants. Three levels of TU [0 (water spray), 10, and 20 mM] were foliarly sprayed after 1 week of salt treatment. Data for various growth and physio-chemical attributes were collected of 64-day-old mung bean plants, while two plants were left for obtaining yield. Salt stress significantly decreased all growth and yield attributes, while increased anthocyanin, relative membrane permeability (% RMP), malondialdehyde, total soluble sugars, total soluble proteins, activities of catalase and peroxidase enzymes, total phenolics, free proline, and glycinebetaine contents. Foliar application of varying TU levels significantly increased shoot and root fresh and dry weights, shoot and root lengths, seed yield per plant, pod fresh and dry weights, number of seeds per plant, 100-seed weight, chlorophyll b (in NM-2006), total soluble sugars, total soluble proteins, POD activity, and total phenolic contents, while decreased RMP (%), total free amino acids, and GB contents. Of the two mung bean varieties, NM-2006 was superior to NM-2011 in most of growth and physio-chemical attributes under both salt stress and non-stress conditions as well as foliarly applied varying levels of TU. Overall, 20 mM TU proved more effective in reducing adverse effects of salt stress in both mung bean varieties.