Studies On Agronomic And Physiological Characteristics Of Different Rice (Oryza Sativa L.) Genotypes In Zn-efficiency And Zn-density In Grain

There is significant difference in tolerance to Zn-deficiency and Zn-content in grain among different rice genotypes(Oryza Sativa L.).The relation between tolerance to Zn-efficiency and Zn-density in grain has not yet been fully understood. In this study a series of solution culture experiments were conducted by using Zn-efficient cultivars IR8192 and Zn-inefficient cultivars IR26,Zn-density in grain cultivars BY and Zn-poor grain cultivars ZHE , to study the relation between Zn-efficiency and Zn-density in grain and morphological and physiological characteristics under different Zn concentration. The main results are summarized as follows:1 .There is significant genotypic difference in Zn-concentration and Zn-distribution in rice grain. BY is significantly higher in Zn content of brown rice and rice shell than other cultivars .It can maintain good growth condition under low Zn-concentration. Under Zn2+0.5 mol/L, BY can grow to 4.97 leaves, fewer than Zn-efficient cultivars IR8192's 5.26 but more than Zn-inefficient cultivars IR26's 4.27 leaves. There is no obvious difference in Zn-content of brown rice between IR8192 and IR26 though there is significant difference in resistance to Zn-deficiency. And BY is Zn -inefficient cultivars in spite of Zn-density in grain. It can be concluded that there is no relation between Zn-efficient and Zn-density in grain and it is possible to screen rice cultivars both Zn-efficient and Zn-density in grain.2. Chlorophyll content and assimilation of CO2 in photosynthesis decreased during Zn concentration decreased.The chlorophyll content increased slightly during Zn-deficiency slightly, and decreased sharply according to heavy deficiency and time elongation. Zn-inefficient cultivars IR26 decreased faster in chlorophyll content than Zn-efficientAbstractcultivars IRS 192, Zn-density in grain cultivars BY decreased more slowly than IR26 but faster than IRS 192 .The chlorophyll content of BY is the highest among the four cultivars under Zn2+2.0jLimol/L and Zn2+0.5 mol/L .It suggests that Zinc content of grain is very important to the growth of rice seedling.3.Gs and Pn changes in the same development trend yet different to Ci development trend under low Zn-concentration. Ci increased while Zn-concentration decreased suggests both stomatal factors and non-stomatal factors affect the Pn of rice .The changes of Ci resulted from the Zn treatment bigger than Gs. It indicates non-stomata factors, decreasing of photosynthesis organism activity is the main reason induced Pn decreasing. Zn-efficient cultivars IRS 192 and Zn-density in grain cultivars BY can keep high photosynthesis rate under low Zn concentration, maybe mainly caused by maintaining high activity of photosynthesis organism.4.Transpration rate of rice was affected greatly by Zn-deficiency .Tr of IR26 and BY decreased obviously but IRS 192 and ZHE changed slightly during Zn-concentration decreased from Zn2+40u.mol/L to Zn2+10 mol/L.5.SOD activity decreased according to the decreasing of Zn-concentration. At Zn2+ 0.5 mol/L, IR26 and BY decreased mostly and became to the lowest in SOD activity, IR8192 changed in a small range.6. MDA content of rice shoot increased while Zn-concentration decreased. At Zn2+0.5 mol/L, MDA content in leaves of IR26increased obviously than IR8192 and BY. Zn-deficiency caused membrane lipid peroxidation of rice shoot. The stress to different rice genotype is different. Heavy Zn-deficient does more harm to Zn-inefficient rice cultivars IR26 than Zn-efficient cultivars IR8192.BY increased in a medium range compared to IR26 and IR8192.7.Relative conductance of rice leaves increased while Zn-concentration decreased. Relative conductance of all genotypes increased rapidly during Zn-concentration decreased from Zn2+10 mol/L to Zn2+ 2 mol/L, compared to the value underZn2+40nmol/L, IR26 increased largest, reached to 322.84%, ZHE increased most slowly, reached to 94.84%, IRS 192 and BY changed in the same development trend and in a medium range.8. H+ excretion of roots was affecte...