关键词: 小麦, 倒春寒, 抗氧化酶系统, 渗透调节物质, 产量

Abstract: Late spring coldness constitutes a significant meteorological threat to the production of winter wheat in China. We simulated late spring coldness under controlled conditions in artificial climate chambers and examined the regulatory effects of foliar-applied 2,4-epibrassinolide (EBR) on low-temperature tolerance across different wheat organs (leaf, stem, and spike) at the booting stage by using the winter wheat cultivar Ningmai 13 as experimental material. The results showed that under low-temperature stress, EBR treatment significantly increased grains per spike, 1000-grain weight, and grain yield by 15.0%, 11.8%, and 29.1%, respectively, compared with the water-treated control. Additionally, EBR treatment enhanced whole-plant dry matter accumulation and promoted the allocation of dry matter to spikes by 27.4%. EBR markedly elevated the activities of key antioxidant enzymes. The activities of catalase and glutathione reductase in leaves increased by 23.1% and 14.1%, respectively. The activities of superoxide dismutase, peroxidase, catalase, and glutathione reductase in stems increased by 22.6%, 18.7%, 20.0%, and 30.1%, respectively. The activities of peroxidase, catalase, and ascorbate peroxidase in spikes increased by 18.7%, 20.2%, and 82.1%, respectively. These responses effectively alleviated membrane lipid peroxidation across all organs, reducing malondialdehyde content in leaves, stems, and spikes by 11.9%, 32.2%, and 27.3%, respectively. Furthermore, EBR treatment significantly increased the content of osmotic adjustment substances. In leaves and spikes, total soluble sugar, soluble protein, and free proline increased by 8.2%, 18.1%, 36.5% and 3.9%, 31.0%, 10.7%, respectively, while stems exhibited increases of 4.0% in total soluble sugar and 72.9% in soluble protein content. In summary, foliar EBR application significantly enhanced the antioxidant and osmotic adjustment capacities of leaves, stems, and spikes under low-temperature stress, systematically improved low-temperature tolerance at the booting stage, promoted dry matter accumulation and its translocation from source to sink organs, thereby effectively mitigating yield losses induced by low-temperature stress.

Key words: wheat, late spring coldness, antioxidant enzyme system, osmotic adjustment substance, grain yield