Effects of drought stress on leaf gas exchange and chlorophyll fluorescence of Salvia miltiorrhiza
干旱胁迫对丹参叶片气体交换和叶绿素荧光参数的影响

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 photosyn thetic rate(P_n)and the maximal photochemical efficiency of PS Ⅱ(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 Pn under drought stress was mainly due to stomatal limitation; while for SA,it was mainly due to non-stomatal limitation.Drought led to a decrease of leaf stomatal conductance(G_s),but induced the increase of water use efficiency(WUE),non photochemical quenching coefficient(q_N),and the ratio of photorespiration rate to net photosyn thetic rate(P_r/P_n),resulting in the enhancement of drought resistance.The increment of WUE,qN,and P_r/P_n was larger for SI than for SA,indicating that SI had a higher drought resistance capacity than SA.