Elevated ozone phytotoxicity ameliorations in mung bean {Vigna radiata (L.) Wilczek} by foliar nebulization of silicic acid and ascorbic acid.

The present work provides an insight into the development of biochemical adaptations in mung beans against ozone (O) toxicity. The study aims to explore the O stress tolerance potential of mung bean genotypes under exogenous application of growth regulators. The seeds of twelve mung bean genotypes were grown in plastic pots under controlled conditions in the glasshouse. Six treatments, control (ambient ozone level 40-45 ppb), ambient O with ascorbic acid, ambient ozone with silicic acid, elevated ozone (120 ppb), elevated O with ascorbic acid (10 mM), and elevated ozone with silicic acid (0.1 mM) were applied. The O fumigation was carried out using an O generator. The results revealed that ascorbic acid and silicic acid application decreased the number of plants with foliar O injury symptoms in different degrees, i.e., zero, first, second, third, and fourth degrees; whereas 0-4 degree symptoms represent, no symptoms, symptoms occupying < 1/4, 1/4-1/2, 1/2-3/4, and > 3/4 of the total foliage area, respectively. Application of ascorbic acid and silicic acid also prevented the plants from the negative effects of O in terms of fresh as well as dry matter production, leaf chlorophyll, carotenoids, soluble proteins and ascorbic acid, proline, and malondialdehyde (MDA) contents. Overall, silicic acid application proved more effective in reducing the negative effects of O on mung bean genotypes as compared to that of the ascorbic acid. Three mung bean genotypes (NM 20-21, NM-2006, and NM-2016) were identified to have a better adaptive mechanism for O toxicity tolerance and may be good candidates for future variety development programs.