多胺对小麦小花退化的调控及其生理机制

Grain number per spikelet is one of yield components of wheat and floret degeneration determined grain number of wheat. So inhibited floret degeneration is the key point of increases grain number per spikelet of wheat. Polyamine significantly affected the young panicle growth of wheat. However, the effect of polyamine on floret degeneration of wheat and the mechanism of that were still unclear. Our previous study suggested that polyamine significantly affected the floret degeneration of wheat. In the present study, the cultivars with different genotype were selected and the irrigation, nitrogen, hormones, and external spermine (Spm), spermidine (Spd), putrescine (Put) was applied respectively. The ratio of floret degeneration was measured and the polyamine levels, the activity of the enzymes regulate the polyamine and the express level of the gene regulate these enzymes in the different organs were measured during the floret degeneration. Based on these results the effect of polyamine on floret degeneration of wheat was analyzed. Besides this, the cytokinin (CTK) and ethylene (ETH) levels and the carbohydrate contents in different organs were measured. According to the relationship of polyamine, hormone (CTK and ETH) and carbohydrate, the objective of the present study was to investigate the effect of polyamine on floret degeneration of wheat and physiological mechanism of that from polyamine metabolism, hormonal mechanism and carbohydrate transportation.

穗粒数是小麦产量构成因素之一，减少小花退化是提高小麦穗粒数的关键。多胺显著影响禾谷类作物幼穗发育。但是，关于多胺对小麦小花退化的调控及其机理，目前还不明确。本课题组预备试验结果表明，外源多胺显著影响小麦小花退化，同时外源多胺对小麦小花退化的调控具有花位效应、多胺种类效应等独特的特点。基于这些特点，本项目拟通过基因型、水氮调控、外源激素等处理，塑造小花退化情况不同的小麦群体，测定小花退化过程中不同花位小花、叶、叶鞘、茎等不同器官内源多胺的合成及其时空变化，结合外源多胺验证试验，从内源、外源2个角度探明多胺对小花退化的影响；同时，以多胺—激素（ETH、CTK）—碳水化合物转运之间的关系为主线，结合多胺调控小麦小花退化的花位及多胺种类效应，从多胺代谢、碳水化合物转运、激素学机制等方面深入分析多胺调控小麦小花退化的生理机制，为采用适宜措施减少小花退化、提高小麦穗粒数提供依据。

穗粒数是小麦产量构成因素之一，减少小花退化是提高小麦穗粒数的关键。前人研究表明，多胺显著影响禾谷类作物幼穗发育，但是关于多胺对小麦小花退化的影响及其生理机制，目前尚不明确。为揭示多胺对小麦小花退化的影响及其机理，本项目分别设置了品种、氮肥和水分等试验，并结合外源多胺喷施对结果进行验证。本项目的主要研究目标为从内源、外源的角度阐明多胺对小麦小花退化的影响及其生理机制。研究结果表明，品种、氮肥以及水分处理均会影响小麦的小花退化和内源多胺含量，亚精胺（Spd）在调控小麦小花退化过程中发挥着关键作用。小花退化率高的品种其幼穗中Spd显著低于退化率低的品种，低氮和干旱处理在加剧小花退化的同时均显著降低了幼穗中Spd含量，幼穗中Spd含量与可孕小花数呈显著正相关关系，而与小花退化率呈显著负相关。这些结果表明，较高的内源Spd含量有利于可孕小花的形成，能显著提高小麦穗粒数。进一步分析表明，从氨基酸向Spd的合成过程参与调控了小麦小花退化，精氨酸和鸟氨酸合成腐胺、腐胺经S-腺苷甲硫氨酸脱羧酶、亚精胺合成酶途径向Spd的合成途径畅通，有利于提高内源Spd的浓度，能够抑制小花退化，提高小麦千粒重。外源施用试验表明，对双大1号（大穗型品种）和西农538（小穗型品种）进行Spd外源喷施，能够提高幼穗内源Spd含量、内源细胞分裂素含量、可溶性总糖和蛋白含量，从而缓解了小花退化。在干旱胁迫下对小麦植株进行Spd外源喷施，能够有效改善小麦旗叶光合能力、优化氮在不同器官间的分配，从而缓解了小麦小花退化，增加了结实粒数。综上，Spd的合成在调控小麦小花退化过程中发挥着重要作用，而Spd通过影响植株叶片光合，植株碳氮分配以及内源激素含量，从而调控了小麦小花退化，进而影响了小麦结实粒数。