灌浆期高温对小麦旗叶与非叶器官光合和抗氧化酶活性的影响

Effect of High Temperature on Photosynthetic Capability and Antioxidant Enzyme Activity of Flag Leaf and Non-leaf Organs in Wheat

为揭示小麦叶与非叶器官抗氧化系统对灌浆期高温胁迫的反应特征,探讨不同品种和不同器官耐热性差异机制,以小麦强耐热品种石家庄8号和弱耐热性品种河农341为材料,于灌浆期用塑料膜搭棚进行增温处理（花后第8天至第22天）,研究高温胁迫对旗叶光合速率（Pn）、叶绿素含量、旗叶和非叶器官中丙二醛（MDA）和脯氨酸（Pro）含量及超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）活性的影响。高温处理下,两品种Pn比正常温度下（对照）低18.7%~24.9%,叶绿素含量低5.7%~6.2%;旗叶、旗叶鞘、穗下节、颖片和籽粒的MDA含量和Pro含量均升高,其中MDA升高幅度为旗叶〉非叶器官,Pro升高幅度为非叶器官〉旗叶。旗叶、颖片、籽粒的SOD活性和旗叶、旗叶鞘、籽粒的CAT活性以及旗叶、旗叶鞘、颖片的POD活性在高温胁迫初期即诱导增强,而其他器官的抗氧化酶活性则在高温持续一段时间后诱导增强,之后随着高温的持续各器官抗氧化酶活性多表现为低于对照,高温解除后旗叶鞘、穗下节、颖片的SOD活性和旗叶、颖片、籽粒的POD活性有恢复迹象,高温对其他器官的SOD和POD活性以及所有器官的CAT活性造成不可逆影响;总体来看,非叶器官持续抗氧化能力和耐热性强于叶片。石家庄8号叶与非叶器官细胞膜稳定性、抗氧化酶活性均高于河农341,显示其整株耐热性强于河农341,这是石家庄8号在高温胁迫下产量下降幅度低于河农341的重要生理基础。因此认为,非叶器官在小麦适应灌浆期高温逆境中发挥重要作用。

Winter wheat in North China has been subject to high temperature stress during grain filling. The purpose of this study was to determine the effect of high temperature on the photosynthetic capability of flag leaf and the antioxidant system of flag leaf and non-leaf organs in winter wheat cultivars Shijiazhuang 8（tolerant to high temperature） and Henong 341（sensitive to high temperature）. High temperature（HT） stress was imposed with a plastic shed from the 8th to the 22 nd day after anthesis, and normal temperature was used as the control. Under HT, the photosynthetic rate and chlorophyll content of flag leaf decreased by 18.7%–24.9% and 5.7%–6.2%, respectively; whereas the malodialdehyde（MDA） and proline（Pro） contents in flag leaf blade, sheath, peduncle, glume and grain increased in different levels. The increased percentage of MDA was higher in flag leaf than in non-leaf organs and that of Pro was higher in non-leaf organs than in flag leaf. Superoxide dismutase（SOD） in flag leaf, glume and grain, catalase（CAT） in flag leaf, sheath and grain, and peroxidases（POD） in flag leaf, sheath and glume were induced at early stage（4 d after treatment） by HT treatment, while the activities of antioxidant enzymes in other organs increased at later stage（7 d after treatment）. Thereafter, the activities of antioxidant enzymes in various organs maintained lower levels compared with those of the control. At the 26 th day after anthesis when HT stress was relieved for four days, the SOD activity in sheath, peduncle and glume and the POD activity in flag leaf, glume and grain began to increase, but the effects of HT on the SOD and POD activities in other organs and the CAT activity in all organs seemed irreversible. In general, the non-leaf organs exhibited higher antioxidant capability and heat tolerance than flag leaf. Compared with Henong 341, Shijiazhuang 8 exhibited higher cell membrane stability and antioxidant activity in leaf and non-leaf organs, leading to a tolerance to HT stress of the whole plant. This might be the physiological basis of smaller percentage of yield loss in Shijiazhuang 8 than in Henong 341 under HT stress. Our results indicate that non-leaf organs of wheat play an important role in adaptability to climate warming.