【摘要】 稀土矿尾砂区地表大面积裸露,土壤结构遭到破坏,保水性能差,植物生长受到严重的干旱胁迫,季节性高温干旱期甚至威胁植物的生存。以稀土矿区周边广泛分布的枫香、木荷、樟树和桉树4种植物为研究对象,对比分析高温干旱条件下4种植物幼苗的光合特征、水分利用效率(WUE)、渗透调节物质和抗氧化酶活性等生理特征及适应性,为稀土尾砂矿区生态修复中植物的筛选提供理论依据。结果显示,高温干旱(空气温度40℃,土壤含水量2%左右)条件下,4种植物的光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和叶绿素(Chl)含量显著低于高温丰水条件(空气温度40℃,土壤含水量15%左右),光合作用受到抑制,WUE升高;不管高温丰水还是干旱条件下,樟树WUE最高;干旱条件下枫香和桉树的丙二醛(MDA),木荷和桉树的可溶性糖、脯氨酸(Pro)和可溶性蛋白,以及所有植物的过氧化物酶活性(超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT))均显著高于丰水条件。隶属函数评价得出4种植物幼苗抗高温干旱的等级为樟树>桉树>木荷>枫香;灰色关联分析发现WUE和可溶性糖与抗旱性关联最大,其次为CAT、Pro和MDA,可溶性蛋白与抗旱性关联最小。其中,樟树通过提高WUE、可溶性糖和CAT来应对干旱,桉树通过可溶性糖和MDA响应干旱胁迫,木荷在Pro调节下体现抗旱性,枫香则通过可溶性蛋白来抗旱。因此,在稀土尾砂植被恢复中关于乔木树种的选择可优先考虑樟树。更多还原

【Abstract】 Mining rare earth minerals by heap leaching processes imposes substantial threats to the soil in rare earth ore areas, including the destruction of soil structures and the exposure of the ground surface over large areas, which together leads to poor soil water retention and severe soil erosion. Consequently, the growth and survival of plants in these areas are likely to be threatened by soil water deficit, especially during the drought season when air temperatures are frequently very high. To improve the ecological environments of rare earth mill tailings, effective restoration strategies are urgently needed, of which screening for suitable plants is a critical step for ecological recovery. In this study, four woody plant species(Liquidambar formosana, Schima superba, Eucalyptus grandis, and Cinnamomum camphora) that are widely distributed around rare earth mine tailings were selected and tested for their physiological responses to drought stress at high temperatures, and the photosynthetic traits, water use efficiency(WUE), osmotic regulation substances, and antioxidant enzymes activities of seedlings were measured. All four species grown under the drought treatment(with soil water content at 2% and air temperature at 40℃) had significantly lower photosynthetic rates(Pn), stomatal conductance(Gs), and transpiration rates(Tr) than those in the wet treatment(with soil water content at 15% and air temperature at 40℃), but there was a higher WUE for seedlings under the drought condition compared to seedlings in the wet treatment. C. camphora had the highest WUE regardless of soil water status. Malondialdehyde(MDA) in L. formosana and E. grandis, the soluble sugar, proline(Pro), the soluble protein in S. superba and E. grandis, and the peroxidase activity of all species under the drought condition were significantly higher than those in wet. The comprehensive evaluation on physiological indexes based on the subordinate function value method indicated that the sequence for drought resistance of the four plants at high temperatures was C. camphora, E. grandis, S. superba, and L. formosana. The gray correlation analysis showed that WUE and soluble sugar had the largest correlation with drought resistance, followed by CAT, Pro and MDA. On the other hand, soluble protein was least correlated with drought resistance. Overall, C. camphora coped with drought stress at high temperatures by improving WUE and accumulating soluble sugar and CAT jointly, while E. grandis coped with drought stress by accumulating soluble sugar and MDA. For the other two species, S. superba responded to drought through the proline regulation, while L. formosana regulated their soluble proteins in resistance to drought. Therefore, C. camphora could be a priority for vegetation restoration in rare earth mill tailings.更多还原