College of Agronomy, Northwest A&F University, Yangling, Shaanxi, PR China.
International Center for Agricultural Research in the Dry Areas (ICARDA), Rabat, Morocco.
Physiol Plant. 2024 May-Jun;176(3):e14321. doi: 10.1111/ppl.14321.
Increasing density is an effective way to enhance wheat (Triticum aestivum L.) yield under limited cultivated areas. However, the physiological mechanisms underlying the reduction in grain weight when density increased are still unclear. Three field experiments were conducted during the 2014-2019 growing seasons to explore the physiological mechanisms by which polyamines affect grain weight formation. The results showed that when wheat planting density exceeded 450 × 10 seedlings ha and 525 × 10 seedlings ha, wheat yield tended to decrease. Compared to moderate density (DM, 450 × 10 seedlings ha), the filling rate of inferior grains was reduced before 25 days after anthesis (DAA) and the active filling period was shortened by 6.4%-7.4% under high density (DH, 600 × 10 seedlings ha), resulting in a loss of 1000-grain weight by 5.4%-8.1%. DH significantly reduced sucrose and starch content in inferior grains at the filling stage. Meanwhile, DH inhibited the activity of key enzymes involved in polyamine synthesis [SAMDC (EC 4.1.1.50) and SpdSy (EC 2.5.1.16)] and induced the activity of ethylene (ETH) precursor synthase, resulting in a significant decrease in endogenous spermidine (Spd) content in inferior grains, but a significant increase in ETH release rate. Post-flowering application of exogenous Spd increased the accumulation of sucrose and starch in the inferior grains and positively regulated the filling and grain weight of the inferior grains, whereas exogenous ETH had a negative effect. Overall, Spd may affect wheat grain weight at high planting density by promoting the synthesis of sucrose and starch in inferior grains.
增加种植密度是在有限耕地面积下提高小麦（Triticum aestivum L.）产量的有效方法。然而，增加种植密度会降低粒重的生理机制仍不清楚。本研究在 2014-2019 年生长季进行了 3 个田间试验，以探讨多胺影响粒重形成的生理机制。结果表明，当小麦种植密度超过 450×10 株/公顷和 525×10 株/公顷时，小麦产量趋于下降。与中度密度（DM，450×10 株/公顷）相比，高密度（DH，600×10 株/公顷）下，低于正常粒的灌浆速率在花后 25 天（DAA）前降低，活跃灌浆期缩短 6.4%-7.4%，导致千粒重损失 5.4%-8.1%。DH 显著降低了灌浆期劣质粒中的蔗糖和淀粉含量。同时，DH 抑制了多胺合成关键酶[SAMDC（EC 4.1.1.50）和 SpdSy（EC 2.5.1.16）]的活性，并诱导乙烯（ETH）前体合成酶的活性，导致劣质粒中内源腐胺（Spd）含量显著降低，但 ETH 释放速率显著增加。花后喷施外源 Spd 增加了劣质粒中蔗糖和淀粉的积累，正向调节了劣质粒的灌浆和粒重，而外源 ETH 则产生了负向调节作用。综上所述，Spd 可能通过促进劣质粒中蔗糖和淀粉的合成来影响小麦的粒重。
