Response of Growth and Other Physiological Characteristics of Sophora Japonica L. Saplings to Drought Stress

Abstract

Potting and continuous drought was applied to study the effect of drought stress (2 days for a treatment interval and 0-14 days of continuous drought) on the growth and photosynthetic characteristics of Sophora japonica L. saplings. The results were received as followed. (1) The ground diameter and height increment of Sophora japonica L. saplings were inhibited under drought stress. There was no significant difference under mild and moderate drought treatments (drought time 2-8 days) compared with the control group in leaf water content and leaf relative water content; and serious drought treatment (drought time > 10 days) was significantly lower than that of control group (P < 0.01).(2) Under drought stress, the content of every photosynthetic pigment of the leaf of Sophora japonica L. saplings was first increased and then decreased, reaching the highest point on the eighth day of drought. After drought stress, the net photosynthetic rate, transpiration rate, stomatal conductance and other aspects of the leaf of Sophora japonica L. saplings presented various degrees of being inhibited.(3) Under the drought stress, several physiological indexes of the leaf of Sophora japonica L. saplings decreased significantly, including the apparent quantum yield (AQY), carboxylation efficiency (CE) of RuBP, light compensation point (LCP), light saturation point (LSP) and CO2 compensation point (CCP), which shows that drought stress can reduce the utilizing and adaptive capacity of Sophora japonica L. saplings to CO2 in the environment.(4) Under drought stress, the content of soluble sugar and free proline in the leaf of Sophora japonica L. saplings increased first and then decreased. They reached the highest in the eighth day of drought but were still higher than that of the control group at the end of the drought stress. (5) Under drought stress, the content of antioxidant enzymes like POD and SOD in the leaf of Sophora japonica L. saplings increased first and then decreased; they reached the highest on the eighth day of drought but were still higher than that of the control group at the end of the drought stress.