Impact of exogenous amino acids on physiological and biochemical responses under salt stress of hydroponically grown lettuce

Soil salinity is a common abiotic stress for plants that is having an increasing impact on international food production. A practical strategy to help mitigate the adverse effects of salinity stress on crop productivity is to increase salt tolerance of crop plants. It has been shown that exogenous application of amino acids is capable of reducing the severity of salinity stress on seed germination and early seedling growth of brassica and cucumber, respectively. The main aim of the present study was to investigate the potential of sulfur containg amino acid, L-methionine to alleviate salinity stress in lettuce (Lactuca sativa L.) for short term exposure to stress (10 days). Reducing destructive effects of lettuce plants grown in saline water was investigated in greenhouse. The experiment was conducted at institute of vegetables and flowes in December, 2018. Lettuce (Lactuca sativa L.) cv. Butterhead grown in nutrient solution supplemented with methionine (0.22 g/L) were treated using two levels two leavels of salt (40mM/L and 80mM/L) respectively. After 30 DAS (days after sowing) plants were transplanted to hydroponics nutrient solution. Eight days after transplanting plants were treated with methionine (0.2g/L) and subjected to NaCl stress after 15 days of treatment (DAT). After 10 days of stress, it was found that lettuce seedling growth was protected from the salt stress. Additionally, plants treated with methionine showed better growth performance than the plants without methionine subjected to stress or control without amino acid and salt stress. It is concluded that methionine also enhance salt tolerance for crop stand establishment in soils with salinity issues. Generally, the application of methionine with (reduced salt amount) 40mM/L NaCl enhanced growth parameters, i. e. plant height; root length; number of leaves per plant; plant fresh and dry weight; leaf relative water content (LRWC); membrane permeability (MP); lipid peroxidation (MDA); total chlorophyll content in leaf; proline; superoxide dismutase (SOD) and peroxidase (POD) activity; and Na, K, Ca content. adversely affected the plant growth in a dose-dependent manner.

Dr Shumaila Khan, an Assistant Professor of Horticulture at Khwaja Fareed Univerity of Engineering and Information Technology. Her core Research areas are Plant nutrition and Plant stress physiology.