RESPONSES OF SOYBEAN LEAVES AND GRAIN YIELD TO WATER STRESS AT REPRODUCTIVE STAGES
A field experiment was carried out as split plot based on RCB design with four replications in 2011 to assess the effects of different irrigation treatments (I1, I2, I3 and I4: well-watering on the bases of 70 mm evaporation from class A pan and irrigation disruptions during flowering, during grain filling and during flowering and grain filling stages, respectively) on some physiological traits and grain yield of three soybean cultivars (Clark, Williams and L17). Results showed that with increasing water stress, leaf temperature increased, while chlorophyll content index, quantum yield of the PSII (Fv/Fm) and grain yield decreased. Maximum leaf temperature and minimum chlorophyll content were observed under water stress. Maximum reduction in Fv/Fm and grain yield per unit area was observed when plants were subjected to water stress during flowering and grain filling stages (I4). Williams produced the highest grain yield per unit area, which related with higher leaf chlorophyll content of this cultivar.