Euchresta japonica is a Class II key protected wild plant in China. The response of photosynthetic characteristics to light intensity and drought was studied by setting different layers of shade nets and watering with different concentrations of polyethylene glycol solution. The results showed that the saturated light intensity of E. japonica leaves was 683.06~907.07 mmol/(m2·s). The maximum electron transfer rates (ETRmax) and the maximum net photosynthetic rate (Pnmax) under single layer shading were higher than those under double layer shading. The ETRmax and Pnmax under single layer shading without drought were the highest of 55.36 and 6.73 mmol/(m2·s), respectively. Under the same shading condition, the Pnmax and the corresponding saturated light intensity of E. japonica decreased with the increase of drought degree. The transpiration rate and water use efficiency under single layer shading were higher than those under double layer shading. The actual photochemical efficiency, photochemical quenching coefficient and non-photochemical quenching coefficient of photosystem II of E. japonica leaves showed no significant difference among different treatments (P>0.05). Euchresta japonica is a semi-sunny plant, whose leaves whose leaves can take advantage of weak light and its plants have strong drought tolerance. Therefore, it is suggested that proper shading and adequate soil water content should be maintained during field return, ex situ conservation and artificial cultivation.
