Effects of Soil Water Conditions on the Transpiration Rate of Cut Branch of Several Tree Species

Abstract

The effects of soil water stress on the stomatal and cuticular transpiration rates were examined by means of the transpiration measurements with cut branches for eight tree species (Pinus densiflora, Cryptomeria japonica, Juniperus conferta, Quercus glauca, Zelkova serrata, Caragana korshinskii, Hedysarum scoparium and H. mongolicum) growing under four different soil water levels. The stomatal transpiration rates for all species were depressed by the water stress sustained during growth period. The reaction time of stomatal closing after leaf detaching was seldom affected by water stress. J. conferta and P. densiflora (new needle) needed relatively long period for their stomatal closing. On the other hand, Q. glauca, Z. serrata and Cr. japonica could close their stomata in relatively short period. Except the cases of P. densiflora and Q. glauca, the cuticular transpiration rates were suppressed with the degree of soil desiccation. Water stress affected on stomatal transpiration rates of Q. glauca and P. densiflora (new needle), and on cuticular transpiration rates of Z. serrata and Cr. japonica. For the xerophite species, such as Ca. korshinskii, J. conferta and P. densiflora (old needle), both rates of transpiration were modified with water stress.