采用称重控水法控制土壤相对含水量分别为(85. 0±2. 5)%(对照)、(67. 5±2. 5)%(轻度干旱)、(50. 0±2.5)%(中度干旱)和(32. 5±2. 5)%(重度干旱),对土壤干旱胁迫条件下九头狮子草[Peristrophe japonica (Thunb.)Bremek.]和圆苞金足草(Goldfussia pentstemonoides Nees)2 年生苗的植株形态及生理特性变化进行了研究。结果表明:经土壤干旱胁迫处理30 d 后供试2 种植物的外部形态均有一定变化,其中九头狮子草主要变化为叶片失绿、变薄且萎蔫、枝条下垂;圆苞金足草主要变化为茎干倒伏、叶片变软且叶柄低垂。随土壤干旱胁迫程度的增加,供试2 种植物叶片的自然饱和亏、临界饱和亏、需水程度、束缚水含量、束缚水与自由水的含量比值、脯氨酸含量和可溶性糖含量均呈逐渐增加的趋势且均高于对照,而自由水含量、最高水势、最低水势和可溶性蛋白质含量均逐渐降低且总体上低于对照。总体上看,在重度干旱胁迫条件下供试2 种植物各生理特性均与对照有极显著或显著差异,而在轻度或中度干旱胁迫条件下部分指标与对照无显著差异。供试2 种植物各生理指标的变化幅度有明显差异,在同一干旱胁迫条件下九头狮子草叶片的自然饱和亏、需水程度、自由水含量、最高水势和最低水势的降幅、脯氨酸含量和可溶性蛋白质含量的降幅均高于圆苞金足草,其临界饱和亏、束缚水含量、束缚水与自由水的含量比值和可溶性糖含量均低于圆苞金足草。综合分析结果表明:供试2 种植物对土壤干旱胁迫均具有一定的耐性,但圆苞金足草具有更强的抵御干旱的生理机制。

Using weighting method for controlling relative water content in soil with (85. 0±2. 5)% (the control), (67. 5±2. 5)% (light drought), (50. 0±2. 5)% (moderate drought) and (32. 5±2. 5)% (heavy drought), changes of plant morphology and physiological characteristics of 2-year-old seedlings of Peristrophe japonica (Thunb.) Bremek. and Goldfussia pentstemonoides Nees under drought stress in soil were studied. The results show that after soil drought stress treating for 30 d, there are some changes in external morphology of two species, in which, the change in P. japonica is mainly leaf chlorosis, thinning and wilting, and branch weeping; that in G. pentstemonoides mainly stem lodging, leaf softening and petiole weeping. As increasing of soil drought stress degree, natural saturation deficit, critical saturation deficit, water requirement, bound water content, content ratio of bound water to free water, contents of proline and soluble sugar in leaf of two species all gradually increase and all are higher than those of the control, while, their free water content, maximum and minimum water potentials, and soluble protein content all gradually decrease and all are lower than those of the control. General, as compared with the control, there are extremely significant or significant differences in every physiological index of two species tested under heavy drought stress, while no significant difference in some physiological indexes under light and moderate drought stresses. There are obvious differences in change range of every physiological index between two species. Under the same drought stress, natural saturation deficit, water requirement, free water content, decreasing range of maximum and minimum water potentials, content of proline, and decreasing range of soluble protein content in leaf of P. japonica all are higher while its critical saturation deficit, bound water content, content ratio of bound water to free water and soluble sugar content all lower than those in leaf of G. pentstemonoides. Comprehensive analysis result indicates that two species tested possess a certain resistance to drought stress in soil, and G. pentstemonoides has a more advantaged physiological resistant mechanism to drought stress.