Effect of exogenous application of salicylic acid on alleviation of drought stress of immature tea (Camellia sinensis L.) plants

Abstract Application of salicylic acid (SA) leads to positive impacts in improving the physiological and growth parameters under drought in other crops. Knowledge on SA regulation on tea is scanty but important especially under drought. Therefore, potential of minimizing the drought effects on tea via exogenous application of SA was studied in a glasshouse at the Tea Research Institute, Talawakelle, Sri Lanka, using one-year-old potted tea cultivars of known drought tolerance (TRI 2025 – tolerant and TRI 2023 – susceptible). Plants were exposed to a drying cycle while they were foliar sprayed with SA in various concentrations (0, 50, 100, 150 and 200 ppm) along with well-watered and no-spray treatments. Data were collected at 18 hours and 3, 7, 14 and 21 days after applying the treatments from randomly selected plants. Physiological parameters were measured along with soil moisture content. Drought stress led to declining of gas exchange parameters (rate of net photosynthesis, transpiration and stomatal conductance), leaf relative water content and increasing accumulation of osmolytes (total soluble sugar and proline) in both tea cultivars compared with well-watered plants. Exogenous application of 150 and 200 ppm SA significantly improved physiological parameters. These results revealed the role of exogenous application of 150 and 200 ppm SA in diminishing the negative effects of drought on tea plants. Exogenous application of SA 150 ppm will therefore be more effective in alleviating the drought impact on immature tea when considering the environmental impact and cost effectiveness.