Abstract:

In order to elucidate the antioxidation mechanism of wheat subjected to post-anthesis high temperature stress, changes of MDA content and protective enzyme activity under high temperature stress at different grain filling stages were studied by using two different heat-tolerance winter wheat (Triticum aestivum L.) cultivars SN1391 and GC8901. High temperature stresses were made from the 8th to 10th day after anthesis (T1) and from the 15th to 17th day after anthesis (T2) respectively by plastic sheds. Antioxidant system in flag leaf could be more efficiently operated in T1 to reduce lipid peroxidation, while the injury of T2 couldn’t be recovered. In T1, the activity of SOD and CAT significantly increased, the increasing time of CAT was later than that of SOD, the two enzymes cooperated with each other so that they could retard the senescence of flag leaf. On the 28th day after anthesis, the MDA content of SN1391 was lower than that of GC8901 in corresponding treatment. The SOD activity increasing extent of SN1391 was much bigger than that of GC8901, and the recovery capability of CAT activity was greater in SN1391 than in GC8901. In T2, the activity of SOD decreased. Although the activity of CAT was higher than that of CK, it couldn’t abate the degree of flag leaf lipid peroxidation efficiently. This indicated that SOD played an essential role in protective enzyme system. The ability of POD eliminating H₂O₂ was diminished in T1 and the activity of POD significantly increased in T2, which probably damaged the leaves and accelerated their senescence. According to the results above we concluded that with the post-anthesis development, the wheat heat tolerance is deteriorated, so field management should be enhanced especially in middle and late grain filling stages in order to ease the injury of high temperature stress.

Key words: Winter wheat, Flag leaf, High temperature stress, Membrane lipid peroxidation, Senescence, Activity of protective enzyme