Effect of Nitrogen and 6-BA on Development of Tillering Bud and Its Physiological Mechanism

Tiller number is a major factor affecting rice yield, nitrogen and cytokinin have substantial regulative effect on tillering of rice. However, little is known on the mechanism of nitrogen and cytokinin regulating tillering bud growth and on the relationship of them during this process. In this study, two rice cultivars (Yangdao 6 and Nanjing 44) were used to investigate the effect of nitrogen and cytokinin on the regulation in tillering bud growth and the changes of nitrogen, carbon and cytokinins in plant during this process. The results showed that both nitrogen and cytokinin promoted the germination of tillering bud, but there was a significant difference in the effect of them on the subsequent outgrowth, nitrogen promoted both germination and outgrowth of tillering bud, however, cytokinin only promoted tillering bud’s germination. Both nitrogen and 6-BA significantly increased cytokinin (Z+ZR and iP+iPR) content in tillering node and promoted activity of nitrate reductase (NRA) in leaf and root, but 6-BA couldn't significantly increase the content of soluble protein, nitrogen and non structural carbohydrate (NSC) in plant. In conclusion, nitrogen and 6-BA may regulate tiller production by two approaches, one is the promotion of endogenous hormones balance and the other is the controlling of carbon and nitrogen metabolism.