Effect of Water Deficit on Water Relations, Photosynthesis and Osmolytes Accumulation of Salvia leriifolia Benth

In order to investigate the effect of water deficit (WD) stress on water relations and some physiological characteristics of Salvia leriifolia Bench., a greenhouse experiment was conducted in completely randomized design with three replications. Irrigation treatments were fully irrigated as control (-0.035 MPa), mild stress (-0.138 MPa), moderate stress (-0.516 MPa) and severe stress (-1.92 MPa). One set of stressed plants were kept constantly in different levels of matric potentials and the other set (Recovery treatments) irrigated to maximum water holding capacity after soil water was depleted in each stress level. Measured parameters were leaf relative water content (LRWC), membrane stability index (MSI), prolin and soluble carbohydrates content, gas exchange parameters, Intrinsic Water Use Efficiency (WUEi) and Intrinsic Gas Exchange Efficiency (GEEi). The results showed that LRWC and MSI in control plants significantly (P≤0.05) were lower than mild stress but decreased 17.3% and 21% respectively in severe stress compared to control. Soluble carbohydrates content was increased with increasing WD levels but it was only significant with control plants. There was strong negative correlation between LRWC and proline content (r= -0.99***), therefore leaves proline content increased twice (1023 nmol per g fresh weight) at -1.92 Mpa compared to control. Results also indicated that gas exchange parameters were not significantly difference in mild WD against control but with decreasing soil matric potential to -1.92 Mpa, net photosynthesis rate (A), transpiration rate and stomatal conductance (gs) decreased 52, 62 and 75 % respectively. In contrast WUEi and GEE increased 35 and 92% respectively.