Relative water content (RWC) of black gram leaves was measured four times during crop growth period for each treatment (with three replications). RWC measurements were performed during four days (before and after irrigation) every other week. On the days of measurement, two to three adult and young leaves in the direction of the sunlight were cut from each plot after Tc measurement at the maximum stress time. They were placed in plastic bags and transferred to the laboratory immediately21. The RWC values were obtained by the following Eq. :29

where FW is fresh leaf weight (g), TW leaf weight at full turgidity (g) and DW leaf weight when dried in oven (g). The FW value was obtained after the leaves were removed from the crop. The leaves were then immersed in distilled water for four hours. After achieving equilibrium, the leaves were removed by forceps and dried gently and their weight (TW) was measured. Finally, the leaves were placed in a paper bag to dry in the oven at 70 °C for 24 h, so that their dry weight (DW) is obtained29,30.