Plant growth retardant increases nitrogen utilization efficiency and harvest index in maize by optimizing the plant horizontal-vertical ratio and vascular bundle morphology

doi:10.1016/j.jia.2025.02.037

Journal of Integrative Agriculture

2026, Vol. 25

Issue (5): 1913-1926 DOI: 10.1016/j.jia.2025.02.037

Crop Science

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Plant growth retardant increases nitrogen utilization efficiency and harvest index in maize by optimizing the plant horizontal-vertical ratio and vascular bundle morphology

Qian Tang^{1, 2*}, Jianhong Ren^1*, Xinru Zhang¹, Cai Wu¹, Yarong Zhang¹, Dahong Bian¹, Guangzhou Liu¹, Yanhong Cui¹, Xiong Du¹, Chuang Wang^2#, Zhen Gao^1#

¹State Key Laboratory of North China Crop Improvement and Regulation/Key Laboratory of Water-Saving Agriculture in North China, Ministry of Agriculture and Rural Affairs/Key Laboratory of Crop Growth Regulation of Hebei Province/College of Agronomy, Hebei Agricultural University, Baoding 071001, China

²College of Resources and Environment, Huazhong Agricultural University, Wuhan 430000, China

Highlights
● Plant growth retardant (EC (an ethephon and cycocel compound)) improves nitrogen utilization efficiency and harvest index.
● The dry matter determines maize nitrogen uptake.
● EC and high-density planting can synergistically improve nitrogen use efficiency in maize.

Abstract
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摘要

提高氮肥利用效率不仅有助于增加玉米产量，还能减轻因氮肥过量使用而对环境造成的负面影响。大量研究已经明确植物生长调节剂和种植密度对玉米抗倒伏能力和氮素吸收利用的影响，但关于植物生长调节剂与种植密度互作对氮肥利用效率的影响却鲜有报道。本试验于2020-2021年开展，设置4个种植密度：4.5、6.0、7.5和9.0株·m⁻²，并在玉米7展叶设3个EC（乙烯利和矮壮素复合剂）喷施剂量：0（CK）、450和900 mL·ha⁻¹。与CK相比，EC处理（尤其是900mL ha⁻¹剂量）显著降低了玉米株高和生物量，同时增加了茎粗、植株横纵比（PHVR，我们将其定义为玉米地上部第一节间茎粗与株高的比值）以及维管束的数量和面积。PHVR和维管束形态与单株干物质转运量及其对籽粒的贡献率呈显著正相关。尽管EC处理降低了玉米的生物量，但促进了干物质的再分配进而提高了收获指数（HI）。EC处理下，干物质积累量降低导致玉米氮素吸收效率降低，同时PHVR和维管束数量、面积的增加则有助于加速玉米植株中氮素向籽粒转运，在不同密度下玉米氮素利用效率（NUtE）较CK显著提高了4.3% - 31.1%。增加种植密度则可以同步提高玉米氮肥吸收效率和利用效率。因此，在高密度下施用高剂量的EC不仅可以显著增强玉米抗倒伏能力，还可以通过促进干物质和氮素的转运显著提高玉米NUtE和HI。

Abstract

Improving nitrogen utilization efficiency is not only beneficial for increasing maize yield, but it can also mitigate the environmental impact of excessive nitrogen fertilizer use. Numerous studies have evaluated the impacts of plant growth retardants and plant density on plant lodging resistance and nitrogen uptake. However, the influence of plant growth retardants on nitrogen utilization efficiency (NUtE) under varying plant densities has been rarely reported. A field experiment conducted in 2020–2021 involved spraying EC (an ethephon and cycocel compound) at the 7th-leaf stage of maize with dosages of 0 (CK), 450, and 900 mL ha⁻¹ at plant densities of 4.5, 6.0, 7.5, and 9.0 plants m⁻². Compared to CK, the application of EC (especially the high dosage) significantly reduced plant height and dry matter, while increasing stem diameter, the plant horizontal-vertical ratio (PHVR, a new index which we define as the ratio of stem diameter of the basal first internode above the ground to plant height), and the number and area of vascular bundles. PHVR and vascular bundle morphology had significantly positive correlations with individual plant dry matter remobilization amount and its contribution to grain yield. Therefore, despite the reduced dry matter weight observed in the EC treatment, the greater dry matter remobilization enhanced the harvest index (HI). However, nitrogen uptake efficiency was not improved with the enhancement of PHVR and vascular bundle morphology, due to a reduction in dry matter accumulation. In contrast, the improved PHVR and vascular bundle were beneficial for accelerating nitrogen translocation, thus increasing NUtE significantly by 4.3–31.1% compared with CK across the plant densities. Increasing density simultaneously improved nitrogen uptake and utilization efficiency. Consequently, a high dosage application of EC under high density could not only significantly enhance lodging resistance but also improve NUtE and HI significantly by promoting the transport of dry matter and nitrogen.

Keywords: maize vascular bundle dry matter remobilization nitrogen use efficiency harvest index

Received: 13 September 2024 Accepted: 21 January 2025 Online: 20 February 2025

Fund:

This work was supported by National Key R&D Program of China (2023YFD2301500).

About author: Qian Tang, E-mail: tangqian1998n@163.com; Jianhong Ren, E-mail: ndrenjianhong@163.com; #Correspondence Chuan Wang, E-mail: chuang.wang@mail.hzau.edu.cn; Zhen Gao, E-mail: gaozhenvision@163.com * These authors contributed equally to this study.

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Qian Tang, Jianhong Ren, Xinru Zhang, Cai Wu, Yarong Zhang, Dahong Bian, Guangzhou Liu, Yanhong Cui, Xiong Du, Chuang Wang, Zhen Gao. 2026. Plant growth retardant increases nitrogen utilization efficiency and harvest index in maize by optimizing the plant horizontal-vertical ratio and vascular bundle morphology. Journal of Integrative Agriculture, 25(5): 1913-1926.

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