高温干旱复合胁迫对构树幼苗抗氧化酶活性和活性氧代谢的影响

近年来,全球气温不断升高,亚热带部分地区夏季高温和临时性干旱现象日益显著,高温与干旱严重威胁着植物的生存与生长。采用盆栽和人工气候室方式模拟不同的温度和土壤水分梯度,研究了高温与干旱复合胁迫对构树幼苗超氧化物歧化酶(SOD)、过氧化物酶(POD)与过氧化氢酶(CAT)活性、活性氧代谢和丙二醛(MDA)含量的影响。结果表明:(1)高温或干旱单一胁迫下,构树幼苗SOD、POD、CAT活性增加,复合胁迫下,SOD和POD酶活性高于单一胁迫,且随着复合胁迫时间延长而升高。SOD活性受温度和土壤水分双因素影响极其显著,复合胁迫对SOD活性有一定程度的叠加效应;(2)复合胁迫下,活性氧代谢物与MDA含量均显著高于单一胁迫,表明复合胁迫加剧对植物的伤害。通过改变抗氧化酶活性以减轻膜脂过氧化的伤害作用是有限的。

Effects of combined elevated temperature and drought stress on anti-oxidative enzyme activities and reactive oxygen species metabolism of Broussonetia papyrifera seedlings

In recent years, under the global climate change scenario, the occurrence of seasonal high temperature and temporal drought phenomena has increased in some subtropical regions. Consequently, the survival and growth of plants are restrained under the combined stress of elevated temperature and drought. In the present study, a pot experiment was performed at the Xiashu Forest Station of Nanjing Forestry University in 2013. One-year-old Broussonetia papyrifera seedlings were grown in 27-cm pots with brown loam soil, using a completely randomized design with four replicates. Seedlings were initially grown in the field environment and then transferred to a controlled greenhouse with three elevated-temperature and soil-moisture treatments, and the effects of combined elevated temperature and drought stress on anti-oxidative enzyme activities and reactive oxygen species(ROS) metabolism were measured in B.papyrifera seedling leaves. The results indicated that under either elevated temperature or drought stress, the superoxide dismutase(SOD), peroxidase(POD), and catalase(CAT) activities of seedlings increased with the increase of stress level. Under the combined elevated temperature and drought stress, the activities of SOD and POD were higher than those under single temperature or drought stress, and increased over stress exposure time. Significant variation was observed in SOD activity of the seedlings between combined stress treatments, revealing the synergistic effects of combined stress on SOD activities. Under the combined elevated temperature and drought stress, ROS, including O₂^- production rates and hydrogen peroxide(H₂O₂) and malondialdehyde(MDA) contents, were significantly higher than those under the single temperature or drought stress treatment, which suggests the limited role of antioxidant enzyme activities in alleviating the damage of the cell membrane of seedlings due to differences in ROS metabolite accumulation.