Leaf water relations of some dipterocarps

The leaf water relations of well watered and shaded small seedlings in nursery and exposed trees of some dipterocarps were studied to assess tolerance and adaptability to drought using the pressure-volume technique. Leaf water potential at which leaf cells lose turgor initially and osmotic potential at full turgor were lower in the exposed trees than in the nursery seedlings. Relative water content of leaves at turgor loss was also lower in the exposed trees. Both leaf dry weight and total volume of water per unit leaf area were greater in the exposed trees than in the nursery seedlings. These results indicate that the capacity of leaves to maintain positive turgor is relatively low in nursery seedlings. Open-grown dipterocarps that experience greater water deficiency develop drought-adapted leaves that are capable of maintaining positive turgor through osmotic adjustment.