中文摘要：

以田间持水量的30％、50％和75％为3个水分处理梯度，研究了决明子和菘蓝2种药用植物在不同水分处理和生长阶段的生长特性，并对稳定碳同位素分辨率（△13C）和水分利用效率（wuE）特征及二者之间的关系进行了分析．结果表明：与田间持水量的50％和30％相比，决明子和菘蓝在田间持水量75％的条件下具有较高的生长指标，说明这2种植物在充足或适当的水分条件下具有较高的生产力．随干旱胁迫程度的增加，决明子和菘蓝地上生物量和总生物量的△13C均逐渐减小，而地上生物量和总生物量的wUE均逐渐增加．决明子和菘蓝在不同水分处理之间各指标差异较小，说明这2种药用植物对干旱胁迫反应不敏感．菘蓝wUE与地上生物量和总生物量均呈显著负相关，决明子wUE与根冠比呈显著正相关．

英文摘要：

Growth characteristics, stable carbon isotope discrimination （△^13C） , water use efficien-cy （WUE）, and their correlation of Cassia obtusifolia and Isatis indigotica were measured at threesoil water levels, i. e. , 30% , 50% and 75% of field water holding capacity （FWHC）, and atthree growth stages. The growth indices of the two medicinal plants at 75% of FWHC were higherthan those at 30% and 50% of FWHC, suggesting that the two medicinal plants could obtain highproduction under sufficient moisture condition. The △13C（ aboveground biomass-based A13C） andA IZCT （total biomass-based △13C） decreased, and the WUEA （aboveground biomass-based WUE）and WUET （total biomass-based WUE） of C. obtusifolia and L indigotica increased with the in-creasing degree of drought stress. The growth indices of the two medicinal plants had little differ-ence in the different water treatments, which indicated that the two medicinal plants were insensitiveto drought stress. Water use efficiency of I. indigotica had significant negative relationships withaboveground biomass and total biomass, whilelation with the root/shoot ratio.