干旱胁迫对蒙古黄芪生长及根部次生代谢物含量的影响

以山西道地药材黄芪一年生幼苗为试验材料,设置常规水分条件(CK)、轻度干旱胁迫(A1)、中度干旱胁迫(A2)、重度干旱胁迫(A3)4个不同处理,研究土壤干旱胁迫对黄芪生长及生理的影响。结果表明:黄芪茎叶快速生长集中在出苗后80—120d,以后生长减缓;当茎叶枯萎时,根中生物量短期快速积累。与常规水分条件相比,干旱胁迫处理显著降低了黄芪苗高及茎叶生物量,但对抗氧化能力、根系生长及次生代谢物积累产生了不同的影响。轻度干旱胁迫下SOD、POD、CAT 3种抗氧化酶活性升高,丙二醛(MDA)含量和细胞膜透性降低,同时根长与根生物量增加、多糖与皂苷两种次生代谢物积累增多,黄芪药材的质量得到显著提高(P0.05);胁迫上升到中度、重度时,SOD酶活性逐渐降低,重度胁迫下低于对照,而POD及CAT酶活性、MDA含量、细胞膜透性均随胁迫增强而升高,相反,根长、根生物量、多糖与皂苷含量降低,导致黄芪药材的质量显著降低(P0.01)。综上表明,干旱胁迫下,SOD酶表现较为敏感,可能在清除活性氧中起主要作用;轻度水分胁迫能有效启动黄芪体内抗氧化酶系统和次生代谢,它们相互协作共同对抗胁迫对细胞产生的伤害,通过降低地上部分的生长,将营养物质优先运往根部,促进根产量及药材质量的提高。这一结论,可在黄芪多糖和皂苷次生代谢物定向培育的水分管理中加以利用。

Effects of drought stress on seedling growth and accumulation of secondary metabolites in the roots of Astragalus membranaceus var. mongholicus

Drought stress usually influences growth and secondary metabolite accumulation in the roots of Astragalus membranaceus var. mongholicus, resulting in varied qualities and medicinal properties. In this study, four different drought treatments (regular soil-water contentCK], mild drought stressA1], medium drought stressA2], and strong drought stressA3]) were applied to evaluate the effects of drought on one-year-old Shanxi native A. membranaceus seedlings. The results showed that an increase in the growth of stems and leaves of A. membranaceus occurred 80-120 d following germination, and then it gradually decreased. A high accumulation of root biomass occurred during the withering period of the aboveground parts of the plants. Drought stress reduced the height and aboveground biomass significantly and affected antioxidant activity, root development, and secondary metabolite accumulation. Under A1 conditions, the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), were raised with increased root length, root biomass, polysaccharides, and saponins. However, the malondialdehyde (MDA) content and cell membrane permeability decreased accompanied with a significant improvement in the overall quality of A. membranaceus (P < 0.05). The SOD activity decreased, and it was lower than that of the control under the A4 conditions. For increased drought stress, the activities of POD and CAT, MDA content, and cell membrane permeability were all increased and consequently resulted in a decreasing in root length, root biomass polysaccharides, saponins and the overall quality of the plant (P < 0.01). In summary, the result showed that the SOD activity was more sensitive to drought stress, suggesting a major function in the resistance to active oxygen. In addition, mild drought stress might promote the interaction between the antioxidant enzyme system and secondary metabolism system in A. membranaceus by increasing resistance to cell damage. The quality and yield of root could be improved by reducing aboveground growth for nutrient transportation to roots to some extent. The results of this study can be applied to promote the production of A. membranaceus with high polysaccharide and saponin contents through water management.