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To clarify the physiological mechanisms by which exogenous brassinolide (Brassinolide, BR) regulates floret degeneration and grain formation in wheat, a spring wheat cultivar Yangmai 15 was used as the material. During the booting stage, plants were sprayed with 0, 0.1, 0.2, or 0.4 mg·L-1 BR. The results showed that compared with un-spraying BR, spraying BR significantly reduced the floret degeneration rate and increased the number of grains per spike and grain weight. The 0.2 mg·L-1 BR treatment was the most effective, increasing grains per spike by 4.76 and grain weight per spike by 7.58%. Spraying BR signifficant improved the chlorophyll content, maximum photochemical efficiency, and net photosynthetic rate from 5 to 25 days after spraying. Spraying BR promoted the accumulation of photosynthetic assimilates and their translocation to the spike. 10 days after spraying, sucrose content in the spike increased by 10.47% under 0.2 mg·L-1 BR; sucrose synthase activity also increased, accompanied by upregulated expression of key sucrose-metabolism genes, including TaSUT1, TaSUS1, TaCWI, and TaAGPL1. Spraying BR modulated endogenous hormone balance in the spike: the 0.2 mg·L-1 BR treatment increased gibberellin content by 13.42%, decreased abscisic acid content by 34.86%, and significantly raised the IAA/ABA and GA3/ABA ratios by 37.10% and 42.71%, respectively. Spraying BR improved endosperm development. After anthesis, the relative areas of amyloplasts and protein bodies in endosperm cells under 0.2 mg·L-1 BR increased significantly with 27.12% and 18.98% respectively. In conclusion, exogenous BR effectively reduced floret degeneration and promoted grain formation by enhancing photosynthetic capacity, optimizing assimilate partitioning, and regulating sucrose metabolism and hormonal homeostasis. This led to higher grains per spike and grain weight per spike, and ultimately increased yield. Under the experimental conditions, the optimal BR concentration was 0.2 mg·L-1.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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