Abstract:

To explore the effects of drought stress on the physiological characteristics and drought resistance adaptation mechanism of the seedlings of the medicinal plant Glycyrrhiza uralensis， one-year-old licorice seedlings were used as materials. Using potted plants with controlled water supply to simulate drought stress， we setted up normal water supply control （CK）， light stress （LS）， moderate stress （MS） and severe stress （SS） gradients， and measured key physiological parameters such as the antioxidant system and osmotic regulatory substances. The results showed that with the intensification of drought stress， the contents of malondialdehyde （MDA） and H₂O₂ in the leaves and roots of licorice generally showed an increasing trend， while the content of {\mathrm{O}}_{\mathrm{2}}^{-} in the roots of licorice in the MS group and the SS group was lower than that of CK. The total antioxidant capacity and peroxidase （POD） of roots both showed a trend of first increasing and then decreasing， while the POD and catalase （CAT） activities of leaves first decreased and then increased， and the superoxide dismutase （SOD） activities of leaves and roots both showed a trend of first increasing and then decreasing. After drought stress， the ascorbic acid （ASA） content， glutathione peroxidase （GPX） and GSSG activities in licorice leaves and roots were all higher than those in CK. In conclusion， studies have shown that licorice seedlings can resist mild to moderate drought stress by enhancing the antioxidant enzyme system in leaves and roots and accumulating osmotic regulatory substances. Severe drought exceeds their physiological tolerance threshold， and the drought resistance of leaves is stronger than that of roots. This result provides a physiological basis for water management and drought-resistant germplasm screening of artificial cultivation of licorice in arid areas.

Key words: licorice, drought stress, reactive oxygen species, antioxidant enzymes

摘要：

探究了干旱胁迫对药用植物乌拉尔甘草（Glycyrrhiza uralensis）幼苗生理特性的影响及抗旱适应机制。以一年生乌拉尔甘草苗为材料，采用盆栽控水模拟干旱胁迫，设置正常供水对照组（CK）、轻度干旱胁迫组（light stress，LS）、中度干旱胁迫组（moderate stress，MS）和重度干旱胁迫组（severe stress，SS），测定抗氧化系统及渗透调节物质等关键生理参数。结果发现，随着干旱胁迫程度的加剧，甘草叶和根中丙二醛（malondialdehyde，MDA）和H₂O₂含量整体呈增加趋势，而在MS组和SS组甘草根中{\mathrm{O}}_{\mathrm{2}}^{-}含量均低于CK组。甘草根的总抗氧化能力和过氧化物（peroxidase，POD）均呈先增加后减小趋势，甘草叶POD和过氧化氢酶(catalase，CAT)活性呈先减小后增加趋势，而甘草叶和根中超氧化物歧化酶（superoxide dismutase，SOD）活性均呈先增加后减小趋势。干旱胁迫后，甘草叶和根中抗坏血酸(ascorbic acid，ASA)含量、谷胱甘肽过氧化物酶（glutathione peroxidase，GPX）及氧化型谷胱甘肽（glutathione oxidized, GSSH）活性均高于CK组。结果表明，乌拉尔甘草苗通过增强叶和根系抗氧化酶系统及积累渗透调节物质抵御轻度至中度干旱胁迫，重度干旱则超出其生理耐受阈值；且叶抗旱表现强于根。研究结果可为干旱区乌拉尔甘草人工栽培的水分管理及抗旱种质筛选提供生理依据。

关键词: 甘草, 干旱胁迫, 活性氧, 抗氧化酶