Plant growth retardants (PGRs) have been widely used to improve lodging resistance in crops like maize. However, unsuitable PGRs concentration and application stage always caused yield penalty. This study delayed PGR application time and increased the PGR concentration to simultaneously enhance lodging resistance and grain yield. We aimed to propose a model for maize production regulation and dwarf breeding. A four-year field experiment was conducted by applying EC (a mixture of ethephon and cycocel) at V7 (7th leaf collar is visible; TV7) and V14 (TV14) stage, respectively. Lodging resistance, leaf area, florets, internode length, carbon isotope distribution, and grain yield were evaluated. The results showed that both TV7 and TV14 significantly improved stalk bending strength and lodging-resistant index compared to the control (CK). TV7 reduced basal internodes length and leaves area, while TV14 shortened the internodes above ear without affecting leaf size. Notably, the decreased stem in TV14 facilitated assimilates allocation to the ear from the leaves above ear traced by C isotope, which could promote kernel set when the number of fully developed florets of each treatment was similar. Indeed, the kernel number per ear was increased by 7.6 % for TV14 but reduced by 7.3 % for TV7 compared to CK, leading to a yield increase of 8.1 % for TV14 and a decrease of 8.1 % for TV7. Hence, delaying the application of EC from V7 to V14 stage can effectively enhance both maize lodging resistance and grain yield. Finally, a model for optimizing the utilization of assimilates by PGRs is proposed, which provides an insight for maize production regulation and dwarf breeding in the future.

中文翻译：

---

通过延迟植物生长抑制剂的施用同时提高玉米产量和抗倒伏性


植物生长延缓剂（PGR）已被广泛用于提高玉米等作物的抗倒伏性。然而，不合适的PGRS浓度和施用阶段总是会导致产量下降。本研究推迟了植物生长调节剂的施用时间并增加了植物生长调节剂的浓度，以同时增强抗倒伏性和产量。我们的目的是提出一个玉米生产调控和矮化育种的模型。分别在V7（第7叶领可见；TV7）和V14（TV14）阶段施用EC（乙烯利和cycocel的混合物）进行了四年的田间试验。评估了抗倒伏性、叶面积、花数、节间长度、碳同位素分布和籽粒产量。结果表明，TV7和TV14较对照（CK）显着提高茎秆抗弯强度和抗倒伏指数。 TV7 减少了基部节间长度和叶片面积，而 TV14 缩短了穗以上的节间，但不影响叶片大小。值得注意的是，TV14中减少的茎有利于同位素从穗上的叶子向穗的同化分配，当每个处理的完全发育的小花数量相似时，这可以促进籽粒凝固。事实上，与 CK 相比，TV14 的每穗粒数增加了 7.6%，但 TV7 的每穗粒数减少了 7.3%，导致 TV14 的产量增加了 8.1%，TV7 的产量减少了 8.1%。因此，将EC的施用从V7阶段推迟到V14阶段可以有效提高玉米的抗倒伏性和产量。最后，提出了优化植物遗传资源同化物利用的模型，为未来玉米生产调控和矮化育种提供了思路。