Influence of Salicylic Acid on the Growth of Lettuce ( Lactuca sativa   var longifolia) During Reduced Leaf Water Potential

Salicylic acid (SA) a signal molecule which is responsible for inducing defense mechanisms in plants and also has a protective role in stress sensitivity. A study was conducted to determine the effect of water deficit stress on the growth of Lactuca sativa L. (Lettuce) using SA (1 mM and 3 mM) during reduced leaf water potential. Plants were subjected to 7 days drought after four weeks of growth. Stressed plants exhibited a lower leaf water potential (ψ_w) of -0.499 MPa as compared with the control (ψw of -0.460 MPa). Plants with lower leaf ψ_w exhibited reduction in almost all the parameters studied: 1 mM SA foliar treatment caused increase of 8 % in plant height and 53.16 % in plant biomass. Foliar treatment of 3 mM SA of the relative water content stimulated 13 % increase in the growth as compared to the control plant which was statistically significant at P<0.05. Overall, SA in stressed plant exhibited higher ameliorative capacity which has the beneficial role of mediating defense response in plants under stress.