Sensitivity of Platycladus orientalis young tree to water stress and its transpiration efficiency at different growth stages during annual growth period
侧柏幼树不同生长阶段对水分的敏感性与蒸腾效率

Using the artificial water control technique in the shed of free-rain and periodically- changing water supply at different growth stages during annual growth period, we examined the sensitivity of young trees to water stress and the relationships between transpiration water-consumption, transpiration efficiency and soil water supply for Platycladus orientalis. The results showed that the transpiration water-consumption was affected by the average amount and procedure of water supply at different growth stages over the annual growth period. Transpiration water-consumption of Platycladus orientalis increased with increasing water supply either at the fast growing and late growth stages when the annual water supply was low or relative soil moisture was no more than 87.84% at any growth stage, or at the early growth stage and fast growing stage when the annual water supply was high or relative soil moisture was more than 87.84% at any single growth stage. The apportionment of water supply among growth stages had a big impact on the transpiration water-consumption, showing the highest sensitivity of Platycladus orientalis to soil water stress at the fast growing stage and the lowest at the late growth stage. However, maintaining relative lower soil moisture at the late growth stage can improve the youngling's growth. The optimum relative soil moisture for WUE was 75.96% at the early growth stage, 73.76% at the fast growing stage, and 69.52% at the late growth stage. A dated water production functions for Platycladus orientalis were put forward for the first time.