外源多胺对小麦小花退化的调控机制

小麦穗粒数与小花退化密切相关，多胺是调控小花发育的一种重要植物生长调节剂。本研究利用小麦品种(系)双大1号(大穗型)和西农538 (小穗型)，于小花退化阶段在穗部施用腐胺(Put)、亚精胺(Spd)和精胺(Spm)，分析外源多胺对小麦小花退化的影响及其与内源激素、植株碳氮的关系。结果表明，外源Spd和Spm显著抑制小花退化、提高了可孕小花数目，而Put加具有显著的负效应；并且多胺的调控具有明显的位置效应，对小穗上部弱势小花退化的调控效应显著大于下部强势小花。施用外源Spd和Spm后，弱势小花中Spd、Spm显著增加，同时玉米素+玉米素核苷(Z+ZR)含量及其与脱落酸(ABA)的比值也显著升高，而内源乙烯的释放速率降低，并且弱势小花中可溶性总糖和可溶性蛋白质含量显著提高。外源Put对弱势小花的控调效应与此相反，施用后弱势小花中Put、ABA含量以及内源ETH释放速率显著提高，而(Z+ZR)与ABA比值和可溶性总糖含量降低。因此认为，多胺参与了对小麦小花退化的调控，其对小麦小花退化的调控与内源激素、植株碳氮代谢密切相关。

Effect of ExogenousPolyamines on Mechanism of Floret Degeneration in Wheat

Kernel number per spike has a close relationship with floret degeneration in wheat, which is regulated greatly by polyamines (PAs), one of important plant growth regulators. In this study, we applied exogenous spermine (Spm), spermidine (Spd) and putrescine (Put) to the young spikes of cultivars Shuangda 1 (large-spike type) and Xinong 538 (small-spike type) to investigate the effects of PAs on floret degeneration,endogenous hormones, and the carbon and nitrogen changes in wheat floret. The results indicated that exogenous Spd and Spm had similar effects on floret degeneration whereas exogenous Put was in function. In the treatments with external Spd and Spm applied, the floret degeneration was inhibited and the number of fertile floretsincreased significantly. In the external Put treatment, floret degeneration aggravated and the fertile floret number decreased significantly. Such influence by external PAswas different in upper and lower florets of a spike and the upper florets (inferior florets) showed greater effects than the lower ones (superior florets). The concerntrations of endogenous Spd and Spm, zeatin (Z) + zeatin ridoside (ZR),and the ratio of Z+ZR-to-abscisic acid (ABA)in inferior florets increased after applying exogenous Spd and Spm. However, the evolution rate of endogenous ethylene (ETH) in inferior floret decreased. As a result, the total soluble sugar and protein contents increased significantly in inferior floret. In contrast, exogenous Put showed reverse effects compared to Spd and Spm. Our results indicate that PAswere involved in the regulation of floret degeneration by changing the endogenous hormone concerntrations and the carbon and nitrogen metabolism in wheat plants.