研究了干旱处理15 d后,大叶型丹参和小叶型丹参2个品种幼苗气体交换和叶绿素荧光参数的变化.结果表明:在干旱胁迫15 d后,大叶型丹参叶片净光合速率（Pn)和PSⅡ最大光化学效率（Fv/Fm)分别下降了66.42%和10.98%，而小叶型丹参的Pn和Fv/Fm分别下降了29.32%和5.47%，干旱胁迫对大叶型丹参Pn和Fv/Fm的影响明显大于小叶型丹参.小叶型丹参Pn下降主要由气孔因素造成，而大叶型则主要由非气孔因素所致.干旱胁迫使丹参叶片的气孔导度（Gs)下降,但明显诱导了水分利用效率（WUE)、非光化学猝灭系数（qN)和光呼吸速率与净光合速率比率（Pr/Pn)的增加，以提高干旱胁迫抗性.其中小叶型丹参的增幅明显大于大叶型丹参.表明小叶型丹参的抗干旱胁迫能力更强.
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 (Pn) and the maximal photochemical efficiency of PSⅡ (Fv/Fm) 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 Pn and Fv/Fm 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-tomatal limitation. Drought led to a decrease of leaf stomatal conductance (Gs), but induced the increase of water use efficiency (WUE), non-hotochemical quenching coefficient (qN), and the ratio of photorespiration rate to net photosynthetic rate (Pr/Pn), resulting in the enhancement of drought resistance. The increment of WUE, qN, and Pr/Pn was larger for SI than for SA, indicating that SI had a higher drought resistance capacity than SA.