| A pot-grown experiment was conducted to investigate the effects of regulated deficit irrigation on morphological characteristics and water use of Jatropha curcas L. Two water deficit levels were set as severe water deficit W1 (soil moisture maintained at 25%～45% of field capacity) and moderate water deficit W2 (soil moisture maintained at 45%～65% of field capacity) and three water deficit time levels (D1: 120 d, D2: 90 d, and D3: 60 d) were designed in the study. Control treatment was full irrigation (soil moisture maintained at 65%～85% of field capacity). Results showed that effects of light water deficiency were more apparent than those of severe water deficiency on plant height, stem diameter, healthy index of seedlings, total leaf area, xylem cross-sectional area of basal shoot, total dry mass, and water use efficiency of Jatropha curcas L. However, severe water deficit level seemed to have affected the root-shoot ratio and Huber value of Jatropha curcas L. more than light water deficit level. Effects of water deficit time on plant height, stem diameter, healthy index of seedlings, total leaf area, xylem cross-sectional area of basal shoot, total dry mass, and water use efficiency of Jatropha curcas L. were in the following order: 60 d＞90 d＞120 d. Additionally, effects of water deficit time on root-shoot ratio and Huber value of Jatropha curcas L. were as 120 d＞90 d＞60 d. Compared with the control, W2D3 treatment saved irrigation water by 11.2%, leaf and petiole dry mass were significantly reduced, and root, stem, and total dry mass dropped slightly. Nevertheless, base stem diameter-plant height ratio and root-shoot ratio became significantly increased. As a result, irrigation water use efficiency and healthy index of sapling were significantly increased to 7.8% and 8.1.%, respectively. It is clear that light water deficit level t the late stage of seedling development not only increased the healthy index, but significantly promoted water use efficiency. |