Effect On Soybean Leaf Light Energy Distribution And Changes In The Characteristics Of Anti-Photoinhibition In The Condition Of Chlorophyll Defcient

Soybean is an important food and oil crop. Increasing soybean yield is one of the most important breeding aims. About 95% of the crop dry matter comes from the photosynthetic assimilation. Therefore, the improvement of the light energy utilization ratio during photosynthetic process is the key for further increasing crop yield and feeding the world's increasing population. For many years, considerable researches have been carried out to breed for genotypes with superior photosynthetic capacity by conventional breeding methods, or rather, by gene transformations.The soybean variety cdl which is a mutation dealed with EMS chemical mutagen and wild-type 86-4 were used as the experiment materials in this paper. The soybeans were cultivated with soil. All the measurements were carried out in 4th health leaves of the main stem. The results are as follows:chlorophyll content of the mutant leaves was lower than that of wild-type significantly, which could be as low as 40% of the wild-type chlorophyll content, and the whole mutant plant was present a clear yellow bud traits. We also can see that the photosynthetic rate of the mutant leaves was little lower than that of wild-type according to the light response curve. It is showed that the decrease of photosynthetic rate is not proportionate to the decrease of chlorophyll content. Chlorophyll deficient induced the decrease of PS II open reaction centers rate and light absorption coefficient. Furthermore, the energy which is used to thermal dissipation in mutant was lower than that in wild-type. And the lack of chlorophyll lead to the decrease of cdl's maximum PSI redox capacity, and the increase of the PQ pool capacity can reduce the electron transport pressure. Another important point is that the xanthophyll cycle in the cdl was activated and replaced the reversible inactivation of PSII in normal leaves.