Effect Of Chlorophyll Deficient And High Nitrogen On Soybean Photosynthesis Capacity

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 assimilates. Therefore, to increase the light energy use 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, either by conventional breeding methods or by gene transformations, to select and breed for genotypes with superior photosynthetic capacity.In this paper, the soybean varieties are a mutation dealed with EMS chemical mutagen and wild-type 86-4.The soybeans were cultivated with soil and midding as well as high nitrogen nutrient solutions.All the measurements were conducted in 4th health leaves of the main stem after one month. The results are as follows:chlorophyll content of the mutant leaves was significantly lower than that of wild-type, about one half of the wild-type's, presenting a clear yellow bud traits. From the result of photosynthetic rate, we can see that photosynthetic rate of the mutant leaves was little lower that of wild-type. It is not proportionate with the decrease of chlorophyll content. Chlorophyll deficient induced a decrease of PS II reaction centers and electron transport rate. Furthermore, the energy used to thermal dissipation was lower than wild-type. But from the excitation energy capture by per PSII reaction centers, we can see, the ABS/RC, TR/RC, ET/RC were all increased in the mutant leaves. It is suggested that the mutant can compensate the deficiency of light energy by increasing the activation of PSII unit reaction centers, we also measured the three compositions of NPQ. The results showed that the relationship of primary and secondary of the three compositions of NPQ has changed in the mutant. The proportionmemt of the mutant depended on qT was increased in the higher light.After cultivating with high nitrogen, net photosynthetic rate were both increased in the wild type and the mutant soybeans,but the extent of increasement in the mutant was greater than the wild type. It is indicated that high nitrogen can increase the content of the cholophyll and photosynthetic capcity in the mutant more efficient than in the wild type, and have the potential of high yield.