Exogenous ascorbic acid mitigates flood stress damages of Vigna angularis

Prolonged water stress adversely affects many aspects of plant physiology, resulting in severe damage to growth and productivity. In response to this and other environmental stresses, plants have evolved complex physiological and biochemical adaptations. To boost existing plant defense mechanisms, this study quantified the negative effects of waterlogging stress and how it may be mitigated by the addition of a natural protective agent. Adzuki beans (Vigna angularis) were grown in commercially available microbe-free soil and subjected to waterlogging stress for 2 weeks. Waterlogging significantly reduced all growth-related variables: shoot length, fresh and dry biomass, chlorophyll content in stressed versus unstressed plants. Waterlogging stress generated reactive oxygen species that heavily damaged plant tissues, causing electrolyte leakage and eliciting an antioxidative response. Specifically, stress-response phytohormone content altered, with a reduction in abscisic acid (ABA) and an increase in jasmonic acid (JA). Furthermore, antioxidants such as malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), polyphenol oxidase (PPO), and peroxidase (POD) were significantly enhanced in waterlogged plants versus non-waterlogged plants. Supplementation of exogenous ascorbic acid (ASC) at 3, 5, and 7 mM revealed that the lowest concentration further reduced ABA and increased JA, enhancing water evaporation rates to raise water-stress tolerance. Moreover, 3 mM ASC also led to lower MDA, CAT, SOD, PPO, POD, and ascorbate peroxidase concentrations in waterlogged plants than in waterlogged plant not treated with ASC. Thus, ASC at a concentration of 3 mM was the most successful in relieving effects of waterlogging stress on plants.