宁麦8号功能叶衰老过程中的光能转化特性

Photo-energy Conversion Characteristics of Functional Leaves from a New Wheat Cultivar Ningmai 8 during Senescence

为探讨小麦衰老过程中的光能转化以及有关生理特性的变化,以大田种植的高产小麦新品种宁麦8号冠层上部的三片功能叶为对象,自旗叶全展时至枯黄,研究其光合速率、叶绿素含量、电子传递活性、叶绿体类囊体膜吸收光谱和抗氧化酶SOD、POD活性,以及MDA含量的变化。结果表明,叶片衰老过程中,净光合速率平稳下降,而叶绿素含量先略有下降,然后逐渐上升,且旗叶的叶绿素含量较倒二叶和倒三叶要高。PS 电子传递活性在前期相对稳定,旗叶全展35d以后其活性明显降低;PS 电子传递活性则经历两个时期,全展28d以前上升,28d后快速下降。PS 和PS 电子传递活性在三片功能叶中的变化趋势基本相同,但倒三叶活性明显最低。与此同时,MDA含量在三片功能叶中均有上升,而SOD则下降,而且倒三叶的含量比旗叶和倒二叶要低,POD的活性在三片功能叶中都是下降的。叶绿体类囊体膜室温下吸收光谱的变化反映出旗叶的总体光能吸收水平要高于倒二叶和倒三叶的,而三者的总体趋势均下降。光能转化及早衰直接影响到光合产物,因此,研究小麦功能叶片的光能转化、有效控制或延缓衰老是进一步发挥增产潜力的有效途径。

The experiment was conducted on physiological and biochemical characteristics, including net photosynthetic rate, the (activities) of electron transport and antioxidases (SOD and POD), and contents of chlorophyll and MDA during senescence period of functional leaves from a newly-developed wheat (Triticum aestivum L.)variety Ningmai.8 grown in the field. The results showed that, with functional leaves senescing, the net photosynthetic rate decreased; chlorophyll content declined between 7~14 d after full expansion of flag leaf, but increased from 14 to 28 d and then started to decrease significantly. The chlorophyll content of flag leaf was the highest among three functional leaves. The electron transport (activity) of PSI was stable (before) the 35 d but quickly declined after 35 d of flag leaf full expansion; (before) the 28 d the electron transport (activity) of PSⅡ were increased but after that decreased. The changing (patterns) of PSⅠand PSⅡ were similar for three functional leaves. With leaf aging, MDA content in these three functional leaves rose, SOD content dropped, lowest for the last third leaf. The (activity) of POD was (reduced) for these three functional leaves. The absorption spectrum of thylakoid membrane at room (temperature) showed that the ability of light absorption of flag leaf was greater than the other two leaves.