水稻叶片发育过程中某些光合组分的变化

Changes of Some Photosynthetic Components During Rice ( Oryza sativa ) Leaf Development

研究了水稻叶片发育过程中,与光合作用及光抑光合有关的某些光合组分的变化。结果表明,在叶片发育初期,光合机构和其功能的建成均表现出一定的顺序性.Chl a的出现早于Chl b,在Chl b的迅速积累期,光合放氧出现。当生长叶由连续黑暗处理转到连续照光下时,短时内,类胡萝卜素含量的下降比Chl a和Chl b的下降慢,分别为15.2％,30.3％,和55.4％,表明类胡萝卜素的光保护作用是有一定条件的。而光合作用保护系统中的另一个关键成分SOD,其活性在光合放氧出现和色素迅速积累之前就达到较高活性,且具有光诱导特性。成熟叶中,高SOD活力是与高放氧速率相关的。在高温处理下(3小时,44℃),成熟叶中SOD活力降低的少,则光合放氧速率降低的亦少。表明SOD无论是在正常或逆境条件下,对稳定和保护光合作用都有重要意义。

Dynamic changes in and relationships among some photosynthetic components were studied with rice leaves. It was found that there was a certain sequence in the establishment of photosynthetic structure and function during the early development of leaves. From the base to the tip of the enlongating leaves, pigment contents increased rapidly. In the chloroplasts grana structures developed from thylakoid lame-llae. Photosynthetic oxygen evolution ( Pn ) reached 9.25 μmol O2/mg protein/hr in the tip but was undetected in the base. After the beginning of greening of etiolated leaves Chl a and Ch1 b appeared in 3 and 6 hours, respectively, and Pn occurred. The photoprotective system against photoinhibition of photosynthesis was developed in company with photosynthesis. In a short time after transferring the growing leaves from darkness to light, carote-noids, as a component in the photoprotective system, decreased 15.2%, less than Chl a ( 30.3% ) and Chl b (55.4%), indicating their limited protective effect. SOD, a vital component in the photoprotective system,showed a photo-inducible property, and reached about 85% of its maximum induced activity when Pn appeared in the greening of etiolated leaves. In the tip, middle and base sections of mature top leaves, SOD and Pn were 25.5, 18.0, 11.9 units/mg protein and 59.0, 40.0, 36.0 umol O2/mg protein/hr, respectively, and short time high temperature treatment showed that Pn decreased less in the sections where SOD was less sensitive to the treatment, indicating a correlation between high SOD activity and high Pn. It is concluded that the developmental sequence of photosynthetic components and the photoprotective system are fundamental to keep photosynthesis high and stable in changeable environments.