Abstract: Effects of drought and enhanced UV-B radiation as well as their combined stress on the UV-B absorbing compounds and osmotic adjustment substances of three Lespedeza species were studied. The contents of osmotic adjustment substances of three Lespedeza species first increased and then decreased. Significant inter-species differences were observed: co-stresses induced more soluble protein than single drought or enhanced UV-B radiation since day 12; co-stresses induced more osmotic adjustment compounds in the last several days; the soluble protein synthesis of L. potaninii in the early stage of all treatments was inhibited. The UV-B absorbing compounds (flavonoids and total phenol) were mainly induced by enhanced UV-B radiation and co-stresses. The MDA contents of three Lespedeza species increased compared to control, which increased less in L. formosa than that in L. bicolor and L. potaninii. According to subordinate function, L. formosa and L. bicolor were of higher antioxidant capacity than L. potaninii. Results suggested that the combined stresses of drought and enhanced UV-B radiation functioned synergistically, which could alleviate the damage caused by each other.

Key words: Enhanced UV-B radiation, Drought stress, UV-absorbing compounds, Osmotic adjustment substances

摘要： 以美丽胡枝子(Lespedeza formosa)、二色胡枝子(L. bicolor)和牛枝子(L. potaninii)为材料,采用盆栽试验研究正常生长(CK)、干旱处理(D)、增强UV-B辐射(U)以及二者复合处理(D+U)下其叶片中渗透调节物质和紫外吸收物质含量的响应。结果表明:3种胡枝子叶片中渗透调节物质含量均较对照呈先升后降的趋势,但存在一定的种间差异。复合处理后期美丽胡枝子可溶性蛋白含量均高于单因子处理下的含量;二色胡枝子可溶性蛋白、可溶性糖和游离脯氨酸的含量在各处理下均呈先升后降的趋势,且在后期复合处理诱导的含量逐渐增大;牛枝子叶片中可溶性蛋白在各处理初期合成受到一定程度抑制。3种胡枝子叶片中总酚和类黄酮对干旱无显著响应,而对增强UV-B辐射和复合处理响应显著。各处理下各胡枝子叶片内丙二醛(MDA)含量均有不同程度的升高,但美丽胡枝子MDA含量升高幅度明显小于另外2种。隶属函数法综合评价得出:复合处理下美丽胡枝子和二色胡枝子具有较强的抗氧化能力,牛枝子抗氧化能力较弱。与单因子干旱胁迫和增强UV-B辐射处理相比,复合处理对植物的伤害程度更小。

关键词: 增强UV-B辐射, 干旱胁迫, 紫外吸收物质, 渗透调节物质