德国景天扦插苗对干旱胁迫的生理响应

以耐旱性较强的德国景天(Sedum hybridum)扦插苗为材料进行干旱胁迫处理(60d),并测定其叶片相对含水量、丙二醛含量、细胞伤害率、光合参数(净光合速率、气孔导度、蒸腾速率)、荧光参数(F_v/F_m、q~P、PHiPS2),以及苹果酸含量、磷酸烯醇式丙酮酸羧化酶(PEPCase)活性等生理指标。结果显示,干旱胁迫导致德国景天叶片相对含水量、光合参数、荧光参数降低,细胞伤害率、丙二醛含量升高;干旱胁迫30d时,各项生理指标变化幅度较小,但40d后变化幅度显著增加,并且德国景天叶片的苹果酸含量和PEPCase活性显著升高,表明C_3光合途径不断减弱,景天酸代谢(CAM)途径被激活,参与了德国景天对干旱胁迫的响应,提高了其耐旱性;当干旱胁迫达60d时,因超过其耐受范围,德国景天受损严重,逐渐死亡。这说明德国景天在生理上表现出极强的耐旱性,并且具有兼性CAM植物的特征,通过CAM途径活化提高植株耐旱性是德国景天重要的耐旱机理。

Studies on the Physiological Response of Sedum hybridum Cutting Seedlings to Drought Stress

Sedum hybridum presents high drought resistance. In this study, the physiological indexes of S. hybridum cutting seedlings were investigated in the 60 days of drought stress, including leaf relative water content, malondialdehyde (MDA) content, cell damage rate, photosynthetic parameters (net photosynthetic rate, stomatal conductance and transpiration rate), fluorescence parameters (F_v/F_m, q^P, PHiPS2), malic acid content and phosphoeno-lpyruvate carboxylase (PEPCase) activity. Results showed that drought stress led to a decrease in leaf relative water content, photosynthetic parameters and fluorescence parameters, and an increase in cell damage rate and MDA content. Within the first 30 days of drought stress, the physiological indexes exhibited small amplitude variation. After 40 days of stress, the variation amplitude of physiological indexes increased rapidly. In the following experiments, malic acid content and PEPCase activity increased significantly, demonstrating that the C₃ pathway was weakened and crassulacean acid metabolism (CAM) pathway was stimulated, which was involved in the stress response of S. hybridum to enhance drought resistance. After 60 days, stress exceeded the tolerance range of S. hybridum plants, leading to serious damage and gradual death. Our results showed that S.hybridum cuttings exhibited strong drought tolerance physiologically, and possessed the characteristics of a facultative CAM plant. Activation of the CAM pathway enhanced drought tolerance, which was an important mechanism of S.hybridum.