Objective The study was conducted to explore the physiological and biochemical response mechanism of Thunbergia Laurifolia mature seedlings to drought.

Method The mature seedlings of T. Laurifolia were selected as the materials, and the pot water control method was adopted.Three water treatments were set, namely, normal water supply (CK), moderate drought stress (MD) and severe drought stress (SD).The morphological index, photosynthetic index and chloroplast ultrastructure were determined.

Result Compared with the control, the morphological indexes such as plant height, ground diameter, number of leaves, leaf length, leaf width and root-top ratio of each treatment all decreased gradually with the aggravation of drought.The diurnal variation of net photosynthetic rate of T. Laurifolia under all treatments had the phenomenon of photosynthesis "napping".Compared with the control, the water use efficiency were higher under MD and SD treatments (0.89 μmol/mmol and 0.77 μmol/mmol, respectively).The chloroplast ultrastructure changed greatly under MD and SD treatments.

Conclusion The mature seedlings of T. Laurifolia could respond to harsh environmental drought conditions by reducing photosynthesis, closing stomata and improving water use efficiency.The chloroplast structure of T. Laurifolia changed under the MD treatment.Although the chloroplast structure was seriously damaged under the SD treatment, no death was observed in the mature seedlings, indicating that the mature seedlings of T. Laurifolia had strong drought tolerance.T. Laurifolia can be applied in landscape because it is more resistant to drought.