Abstract:In order to understand the physiological adaptability of Clerodendrum inerme to tropical coral islands, the photosynthetic and stress resistance characteristics of C. inerme were studied under different water and nitrogen treatments. The results showed that watering frequency had greater effects than nitrogen treatment on physiological characteristics of C. inerme. The chlorophyll (Chl) a content and Chl a/b were the highest under low watering frequency with significant difference under other watering frequencies. The net photosynthetic rate (Pn), stomatal conductance (Gs) and water use efficiency (WUE) under low watering frequency were significantly higher than those under high watering frequency, while the transpiration rate (Tr) was significantly low, showing better photosynthetic capacity and water use efficiency. The proline (Pro) content under medium watering frequency was the highest with (5.04±1.21) mg/g, which could reduce the osmotic pressure and increase water absorption under drought stress; the relative conductivity under low watering frequency was the lowest with 0.17±0.03, which could reduce membrane system damage caused by drought stress. Therefore, Clerodendrum inerme has a good adaptability to drought and barren habitats in tropical coral islands.