Screening Of Soybeans With High Phosphorus Absorption Efficiency And Their Responses To Different Phosphorus Levels

Phosphorus deficiency was one of the important limiting factors to produce soybeans. Improving P-effeiciency in soybean made it economically and efficiently to solve the question. This study collected 226 soybean varieties in the northeast, which were experimented in field without P fertilization compared to that in the same soil supplied with P fertilization, and were studied on the difference of morphology and physiology. On the basis, we explored the difference of P-efficient among different soybean genotypes and analysis the growth indexes of plant(including fresh weight﹑dry weight﹑P content in root and shoot of plant) and relative physiological index (including soluble protein content﹑APase activity﹑and soluble﹑P content) through water culture and sandy culture to study the difference of soybean P-efficient genotype and mechanism. The study was expected to provide basis in material and theory. The results were as follows: 1 Screening on soybean P-efficient genotype in field and difference of yield index There were significant difference in grain yield﹑plant height﹑node﹑branch ﹑hundred-seed weight and florescence, which were affected significantly by P-sufficient level, for different soybean genotypes. Based on cluster analysis to relative yield some morphology index, we selected 43 P-efficient and P-inefficient soybean varieties. In the next year, 5 P-efficient and 4 P-inefficient genotypes were selected by the same ways. Under P stress, plant height﹑branch,node and hundred-seed weight changed significantly and there were different in different phosphorus genotypes. 2 Analysis of physiology and cultivation index of different soybean genotypes in field. Under soil cultivation condition, photosynthetic rate which decreasing range corrected with the difference in genotypes showed decreasing trend in both P treatment and compare. Changes of chloroplast pigment content showed the life of soybean shortened, and the average days was 7,the difference in genotypes no significant; The accumulation of plant dry weight conformed to Logistic equation whose parameters had changed between treatments and genotypes; P content in exudates and bleeding liquid decreased and had difference in genotypes; Root volume and water content around roots decreased and had difference in genotypes. 3 Root parameter and leaf analomical structure of different soybean P-efficient genotypes in sandy culture. The study on changes of root morphology under P deficiency stress showed that low-P stress during short time induced root extension﹑root diameter becoming thin﹑root surface area increasing and root system activity increasing. Comparing the changes of roots under P deficiency stress, we concluded that root-shoot ratio and length of root increased, and the difference was significant between P-efficient and P-inefficient genotype during initial stage of P deficiency stress. The relative indexes in roots showed opposite changes under long time P deficiency stress compared with that of short time because of the lace of photosynthate. Under P deficiency stress, plant showed short﹑small and inclined yellow leaves. Analysis on anatomical structure of leaves showed ⑴cell numbers of new leaf per area increased and ranked in close together.⑵l eaf thick increased.⑶changes of thick of middle and below leaves were not significant and cell structure loose.⑷changes of new leaf thick was not connected with genotypes.4 Changes for physiology indexes of different soybean P-efficient genotypes in water culture Under P deficiency stress, study on membrane liqid peroxidation showed MDA content of soybean was far higher than control's with the prolonged stress duration. It could be concluded that P deficiency stress increase the membrane lipid peroxidation in soybean. The results showed protective enzyme(SOD POD CAT)activity decreased after appearing a peak with the duration of P stress and had difference in genotypes. The above results probably indicated that the changes of protective enzyme(SOD POD CAT)activity and the ability of scavenging O–were one of the physiological mechanism of deficiency phosphorus tolerance. Under P deficiency stress, other physiological indexes in soybean were studied. The results showed that ⑴Pro content﹑electrolyxe efflux conductivity and APase activity all increased.⑵leaf wax content and stomatal aperture decreased.⑶leaf area﹑the relative water content and soluble protein content decreased.⑷The soluble sugar content increased.⑸P content in every part of plant decreased and decreasing range differed 10 times.⑹Phosphorus concentrated again in plant and P content decreased in root but that increased in aerial part of plant.