Abstract: Taking the seedlings of Salvia miltiorrhiza cv. Sativa（SA) and S. miltiorrhiza cv. Silcestris（SI) as test materials, this paper studied the effects of drought stress on their leaf gas exchange and chlorophyll fluorescence parameters. After 15 days of drought stress, the net photosynthetic rate (P_n) and the maximal photochemical efficiency of PSⅡ (F_v/F_m) of SA were decreased by 66.42% and 10.98%, whereas those of SI were decreased by 29.32% and 5.47%, respectively, compared with the control, suggesting that drought stress had more obvious effects on the P_n and F_v/F_m of SA than of SI. For SI, the reduction of P_n under drought stress was mainly due to stomatal limitation; while for SA, it was mainly due to non-tomatal limitation. Drought led to a decrease of leaf stomatal conductance (G_s), but induced the increase of water use efficiency (WUE), non-hotochemical quenching coefficient (q_N), and the ratio of photorespiration rate to net photosynthetic rate (P_r/P_n), resulting in the enhancement of drought resistance. The increment of WUE, q_N, and P_r/P_n was larger for SI than for SA, indicating that SI had a higher drought resistance capacity than SA.

Key words: drought stress, Salvia miltiorrhiza, as exchange, hlorophyll fluorescence, flue-cured tobacco, phosphorus, root system.