Evaluation of Physiological Characteristics Related to Water Deficit in Some Genotypes of Sesame (Sesamum indicum L.)

Investigation of physiological responses to water deficit in sesame (Sesamum indicum L.) genotypes can help to identify effective mechanisms of plant resistance to stress. Therefore, chlorophyll content, proline, soluble carbohydrates, net photosynthesis rate, stomatal conductance, maximum quantum efficiency (fv/fm), plant height and shoot dry weight in a complete block factorial pot experiment with three replications were conducted at the College of Agriculture, Isfahan University of Technology, Isfahan, Iran. Four levels of irrigation included irrigation when the soil, water potential of pots was approximately -0.2 MPa (control) =W1, -0.5 MPa (low water deficit) =W2, -1.0 MPa (intermediate water deficit) =W, and -1.4 MPa (severe water deficit) =W4 and 12 sesame genotypes. The highest reduction in chlorophyll content (46%) in the severe water deficit and the genotype was Non-branching Naz. Net photosynthesis rate, stomatal conductance, total chlorophyll content and maximum quantum efficiency (Fv/Fm) were decreased by 43.8%, 39.6%, 46.6% and 17.7%, respectively, compared to control. Proline and soluble carbohydrate content of sesame genotypes was increased by 129.8% and 35.6%, respectively, under severe water deficit compared to control. Plant height and plant dry weight decreased with severe water deficit by 21.5% and 52%, respectively, due to severe water deficit. Severe water deficit, with negative effects on photosynthetic systems by limiting stomatal conductance and reduce the net photosynthesis rate, was due to the decrease in maximum quantum efficiency. Decrease in maximum quantum efficiency on one side and the chlorophyll content reduction in other side, reduces the photosynthetic production and reduce the yield (dry matter) per genotypes.