Studies On Agronomic Traits And Nutrition Mechanism Of Genotypes With Zn-rich In Grain

Recently, it was found that the most aboard area decrease of rice output in the word is due to the deficiency of zinc. And zinc deficiency is one of the most important nutrition deficient elements inferior to that of phosphor and nitrogenous. In the mean time, zinc is not only the necessary nutrition element to humans, but also one of the three most easily absent microelement Zn, Fe, V_A Although many researchers have studied on the nutritional genotypic difference of zinc in rice, most rest on phenotypic description without deeper researching on the physiological and biochemical mechanism. Therefore, there was no uniform and credible screening guideline. In this study, the genetic mechanism of rice of Zn-rich in seed was researched by the investigation of the agronomic characteristics and physiological and biochemical changes. And it also provided theoretical gist and practical guidance for screening and cultivating rice of Zn-rich in seed. The major results obtained were summarized as follows:1. There was significantly genotypic difference in root morphological traits. As Zn²⁺ activity decreased from pZn²⁺9.7 to pZn²⁺10.3, Zn-efficient genotype IR8192 could more effectively increase root length and root absorbing area by contrast with Zn-inefficient genotype IR26;Zn-rich in seed genotype BY could more effectively increase root volume, root fresh weight, root dry weight and root absorbing area by contrast with Zn-poor in seed genotype Z921. It was proved that root length and root absorbing area of rice seedlings could be used in screening Zn-efficient genotypes.2. Kinetic parameters of Zn²⁺ uptake by root which were determined at low Zn²⁺ activity could response better to difference by the absorbing ability in root of rice seedlings. At low Zn²⁺ activity, C_min, I_maxand β values of IR8192 were smaller than those of IR26, which was showed that root of IR8192 had better congeniality to Zn²⁺ and Zn absorption efficiency increased;I_maxand a values of BY were larger than those of Z921, Km, β and C_min values of BY were smaller than those of Z921, which were expressed that root of BY had better congeniality to Zn²⁺ and Zn absorption efficiency increased, and there were more Zn²⁺ influxto BY. It also could be concluded that there would be more study to improve p and Cmin values in root of rice seedlings had the correlation to Zn-efficient genotypes, and Km, p\ Cmin and Imax values in root of rice seedling had the correlation to Zn-rich in seed genotypes.3. As Zn2+ activity increased from pZn2+9.7 to pZn2+10.3, photosynthetic rate of IR26 improved significantly, whereas which of the others genotypes didn't change significantly. It might because that the best of Zn2+ activity to IR26 was higher than pZn2+9.7. The largest Fv/Fm of BY indicated that the ability of restraining lightfastness of BY was the best.4. As Zn2+ activity increased from pZn2+9.7 to pZn2+10.3, zinc partitioning into rice shoot from root increased with the elevation of Zn supply for BY and Z921 in tillering and initial booting stages. Moreover the amount of Zn uptake increased as Zn2+ activity increased in all genotypes.5. At different Zn2+ activity, the amount of Zn uptake in root and shoot obviously increased more than those without Zn supply since initial booting stage. Though the biomass of BY was significantly less than Z921, the amount of Zn uptake in BY was more than Z921. And the biomass and Zn uptake in spike of BY with Zn supply at different Zn2+ activity were more than those of Z921. The amount of Zn uptake in BY was more significantly decreased when those without Zn supply since initial booting stage. Thus The amount of Zn uptake in booting stage might be one of the mechnism of Zn-rich in seed.