The leaves were tightly wrapped in aluminum foil, frozen at −80 ◦C, and stored in liquid nitrogen. After thawing, sap was collected from syringes at 25 ◦C and placed in the osmometer (Rodríguez-Gamir et al., 2010). Osmolyte content (mmolkg−1) was converted to MPa using the Van’t Hoff equation. The osmotic adjustment (OA) was determined as the difference between the osmotic potential of the leaves at full turgor for control plants and the stressed plants (Garcia-Sanchez et al., 2007).