氮素对水稻分蘖芽发育的影响及其作用机制

[目的]本文旨在探索营养生长时期氮素对水稻分蘖芽发育的影响，为水稻理想株型与合理施肥提供理论基础。[方法]以水稻品种‘日本晴’为试验材料，通过水培试验，探究氮素对水稻分蘖芽形成和生长的影响；比较不同氮素浓度下分蘖数量、分蘖芽的活跃度；观察在缺氮条件是否影响分蘖芽形成；检测休眠芽和活跃芽内基因表达情况；分析独角金内酯相关基因的突变对氮素调控分蘖芽的影响。[结果]不同氮素浓度（0、0.2、2.5和5 mmol？L-1）处理下，营养生长时期水稻分蘖数量随着氮素浓度的降低而减少；缺氮条件下，水稻分蘖芽的形成没有受到影响，伸长受到抑制；在0、0.2、2.5和5 mmol？L-1氮素处理下，水稻在培养到4叶期时，分蘖芽活跃度没有明显变化，当培养到5叶期时，2.5和5 mmol？L-1氮素处理下第3个分蘖芽活跃度明显高于0和0.2 mmol？L-1氮素处理。定量RT-PCR分析结果表明：活跃芽内细胞分裂相关基因表达量明显高于休眠芽；独角金内酯相关突变体表型分析显示：氮素调控分蘖芽生长不受独角金内酯的影响。[结论]营养生长时期，氮素浓度对水稻分蘖芽生长有明显影响，低氮明显抑制了分蘖芽的伸长但不会影响其形成，并且细胞分裂可能参与了氮素调控水稻分蘖芽的伸长，这一过程可能独立于独角金内酯途径。
[Objectives] This study was to investigate the regulation of tiller buds development at vegetative stage by nitrogen in rice,which will provide the theoretical basis of the ideal plant type and reasonable fertilization. [Methods] Rice cultivar‘Nipponbare’was used as the plant material. In the hydroponic system,the regulation of rice tiller bud development by nitrogen was studied. The tiller bud number and activity were compared under different nitrogen concentrations(0,0.2,2.5 and 5 mmol？L-1). The initiation of tiller bud was observed. The gene expression was studied and the influence of strigolactone through nitrogen regulation was analyzed. [Results] Under different nitrogen concentrations during vegetative stage,the number of rice tiller decreased when the nitrogen supply reduced. When nitrogen supply was blocked,the initiation of rice tiller bud was not affected while its elongation was suppressed. The tiller bud was developed at the same stage when the 4th leaf of rice was fully expended. When the 5th leaf was fully expended,the 3rd tiller bud was much longer under 2.5 and 5 mmol？L-1 nitrogen compared with 0 and 0.2 mmol？L-1 nitrogen. RT-PCR results showed that cell cycle marker genes were higher expressed in the active buds which grew much longer. Phenotypic analysis of strigolactone mutants showed that strigolactone was not required for the nitrogen regulation. [Conclusions] During the vegetative stage,nitrogen concentration has a significant effect on rice tiller bud growth,and low nitrogen suppresses the tiller bud outgrowth but does not influence on the tiller bud initiation. Cell division was involved in the tiller bud regulation by nitrogen which may be independent of strigolactone pathway