Objective Seedling growth, morphology and physiological characteristics of Triadica rotundifolia and Croton lachnocarpus were investigated under drought stress to provide scientific basis for species selection and artificial reforestation in the limestone region of South China.

Method Pot culture experiment was applied in this study to simulate drought stress by watering frequency.The physiological indicators were measured with comventional methods.

Result and conclusion The results showed that height growth of T.rotundifolia and C. lachnocarpus declined by 2%-5% and 8%-10% respectivly, while basal diameter growth increased by 17%-35% and 10%-30% respectivly under drought stress. Seedling aboveground biomass, underground biomass, total biomass, and root-shoot ratio could be enhanced by light drought stress, but they declined with the increase of drought stress. Results of physiological examination showed that the soluble protein content, peroxidase (POD) activity, activity of superoxide dismutase (SOD), and malondialdehyde (MDA) content varied with species and drought stress. Soluble protein content and POD activity were more sensitive than the activity of SOD and MDA content. Comparison of the stem anatomical structure showed that there were differences in the structure of cortex, phloem, xylem and marrow. Drought would result in increasing ratio of xylem and marrow, which indicated that they could adapt to drought stress by adjusting xylem and marrow structure. Analyses of subordinate functions showed that the drought tolerance of T.rotundifolia were higher than that of C. lachnocarpus under various drought stresses. They may possess different resistance mechanisms to drought stress based on their difference in physiological responses and stem anatomical structures.