Abstract: Cadmium (Cd), one of the most ecotoxic heavy metals, severely inhibits growth and development of crops. We investigated the effects of foliar spraying diethyl aminoethyl hexanoate (DA-6) on morphogenesis, photosynthetic pigment content, osmotic regulatory substances, and antioxidant defense systems in two cultivars of mung bean (Lyufeng 2 and Lyufeng 5) at the seedling stage under 100 μmol·L^-1 Cd stress in a pot experiment. The results showed that foliar spraying DA-6 increased total chlorophyll content, soluble sugar content, and antioxidant enzyme activities. The POD and CAT activities in Lyufeng 2 were increased by 35% and 197% respectively, while those in Lyufeng 5 were increased by 204% and 378% respectively. However, SOD activity in both cultivars declined under Cd stress. Foliar spraying of DA6 improved glutathione metabolism (P<0.05). In particular, the GSH content of Lyufeng 2 was increased by 30%, GSSG was significantly decreased by 78%, and the GSH/GSSG ratio was increased by 458%. For Lyufeng 5, the GSH content was increased by 53%, GSSG was significantly decreased by 84%, and the GSH/GSSG ratio was increased by 617%. DA-6 could effectively alleviate Cdinduced growth inhibition in mung bean seedlings through synergistic activation of the POD-CAT antioxidant system, reconstruction of glutathione redox homeostasis, and increase of photosynthetic pigment content. Notably, Lyufeng 2 and Lyufeng 5 showed maximum increases of 59% and 51% in stem diameter and 107% and 78% in total dry biomass, respectively. Our results provide theoretical basis and technical support for the application of exogenous plant growth regulators to alleviate Cd stress in crops.

Key words: mung bean, cadmium stress, plant growth regulator, diethyl aminoethyl hexanoate (DA-6), regulatory role