Individual and combined effects of selenium and silica on enhancing the heat tolerance of lentil (Lens culinarisMedik.) genotypes

A serious threat across the world is the environmental stress that affects plant growth and development. To maintain crop growth and yield during stressful environment, various strategies are being evaluated to induce thermo tolerance. In the present study, an indoor experiment was performed under controlled environment with the aim to alleviate the effects of heat stress on lentil plants at vegetative stage through exogenous application of selenium (Se) and silica (Si), individually or in combination. To begin with, we evaluated the reaction of a heat-tolerant (HT) and a heat-sensitive (HS) genotype to varying degree of heat stress under controlled environment. The plants (15-d old) were subjected to 30/20 °C, 35/25 °C, 38/28 °C, 40/30 °C; as day/night temperature, along with controls (30/20 °C). A drastic reduction in shoot and root growth was reported at 38/28 °C, and at 40/30 °C, the plants could not survive beyond 7 days. In a subsequent experiment, we selected the temperature of 35/25 °C to test the effectiveness of exogenously-applied selenium (Se) and silica (Si). Se and Si were supplemented (as soil drench initially, and as foliar spray at 7 days after heat stress), in a range of 1–10 µM concentrations, independently or in combination, to heat-stressed lentil genotypes. It was found that the effects Si were more prominent in improving the water status of the leaf, membrane integrity, chlorophyll content and photosynthetic ability, while Se exerted primarily by reducing the oxidative damage. The combined treatment of Se and Si proved to be more beneficial compared to their individual treatments in declining the adverse impacts of heat stress in lentil genotypes, which might be ascribed to combination of unique effects of each element.