Proline as one of the secondary metabolites was determined according to the method described by Bates et al

Proline as one of the secondary metabolites was determined according to the method described by Bates et al. (1973). Fresh leaf material (0.5 g) was homogenized in 10 ml of 3% aqueous sulfosalicylic acid and was centrifuged at 10,000 × g for 10 min. Afterward, 1 ml of the filtrated mixture was mixed with 1 ml of acid- Ninhydrin and 1 ml of glacial acetic acid in a test tube. The mixture was placed in a water bath for 1 h at 100° C. The reaction mixture was extracted with 4 ml toluene and the absorbance was measured at 520 nm with a spectrophotometer (Model Shimadzu UV- 1601, Shimadzu Corp., Japan).
During the measurement period of physiological variables, drought stress significantly (P? 0.01) reduced stomatal conductance by approximately 43% in 2016 and 50% in 2017 (Figure 3 a, b). KCPF application decremented stomatal conductance at all levels of drought stress and maximum decrease in stomatal conductance was = % observed in severe drought stress level (50 % FC) with 7 % KCPF application in both seasons (Figure 3 a, b).