Physiological and biochemical changes in rice associated with high night temperature stress and their amelioration by exogenous application of ascorbic acid (vitamin C)

Significant efforts are required to enable rice plant to cope with the menace of high night temperature (HNT) stress. As an immediate solution, use of plant growth hormones can be targeted to maximize plant tolerance against HNT stress. Ascorbic acid (AsA) is a small water soluble molecule which acts as an antioxidant and can directly detoxify active oxygen species. In this study, the potential role of AsA has been investigated for the alleviation of HNT related problems by improving the overall anti-oxidant status and physiological performance of rice. In this regard, the current research was carried out in controlled environment to study the interactive effect of HNT and foliar application of AsA on physiological traits of rice; mainly focusing on its anti-oxidative and nutrient status. Two tested genotypes showed considerable similarity in response to both HNT and AsA. HNT increased the malondialdehyde (MDA) content of both varieties and exogenous AsA reduced it almost to the level of control night temperature (CNT). Similarly, the HNT associated increases in Na and K in both root and shoot were also lowered by exogenous AsA. The anti-oxidative enzymes catalase (CAT) and peroxidase (POD) were also increased under HNT. While application of AsA led to reductions in their concentrations. POD was more sensitive to HNT than CAT and AsA also showed more pronounced effect on POD compared to CAT. Although preliminary results for the acclamatory role AsA under HNT are favorable, future detailed studies including diverse genotypes and different levels of AsA applied at various stages are imperative.