Context

Ideotype root system architecture is crucial for achieving high yields in maize by enhancing lodging resistance and nitrogen absorption, particularly under high planting densities. However, there is limited research on this topic in maize.

Objective

The objectives of this study were to reveal the relative importance of different root system traits in root anchorage strength and nitrogen absorption, and to investigate their variations in response to increased plant density.

Methods

To clarify this, a two-year field experiment was conducted in 2018 and 2019, involving four different lodging resistant maize genotypes and two plant densities. Root system traits including root crown architecture, root morphology per whorl, and root distribution in upper and lower soil layers were fully characterized. Root lodging resistance and nitrogen absorption capacity were quantified through artificial root lodging tests and ¹⁵N labeling, respectively, based on measuring root lodging rate and plant nitrogen content.

Results

In comparison to lodging susceptible genotypes XY335 and XD20, lodging resistant genotypes LS1 and FM985 exhibited stronger root anchorage strength and lower root lodging risk. These characteristics were primarily attributed to their wider root crown width, larger projected root area, larger root angle, thicker brace roots, and wider distribution of the root system in the upper soil layer. However, LS1 was unfavorable for nitrogen absorption due to the larger root skeleton increased metabolic costs of soil exploration, which led to reduced root elongation, shallower rooting depth, and thus limited nitrogen acquisition from the soil. FM985 demonstrated a comparable nitrogen absorption capacity to XY335 (slightly higher than LS1) mainly because of the larger growth angle of the outermost crown root and greater specific root length of embryonic roots. With increased plant density, LS1and FM985 had larger reductions in root system traits, but maintained a larger root crown architecture than that of XY335 and XD20, leading to a lower lodging risk. XY335 and XD20 exhibited a stronger capacity for nitrogen acquisition at high plant densities, attributed to the increased root surface area, root volume and root dry matter of embryonic roots and root dry matter in the subsoil.

Conclusions

Taken together, maintaining an optimized root crown architecture, coupled with an increase in surface area, volume and dry matter of embryonic roots and root dry matter in the subsoil, appears to be a more feasible approach for reducing lodging incidents and enhancing nitrogen absorption at a dense population.

中文翻译：

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优化根系结构提高玉米高密度下根系固着强度和氮素吸收能力

语境

理想型根系结构对于通过增强抗倒伏和氮吸收来实现玉米高产至关重要，特别是在高种植密度下。然而，关于玉米这一主题的研究有限。

客观的

本研究的目的是揭示不同根系性状在根系固着强度和氮吸收方面的相对重要性，并研究它们对植物密度增加的响应变化。

方法

为了澄清这一点，我们于 2018 年和 2019 年进行了为期两年的田间试验，涉及四种不同的抗倒伏玉米基因型和两种植物密度。根系性状包括根冠结构、每轮根形态以及根在上下土层的分布得到了充分表征。在测量根系倒伏率和植物氮含量的基础上，分别通过人工根系倒伏试验和¹⁵ N 标记来量化根系抗倒伏性和氮吸收能力。

结果

与易倒伏基因型XY335和XD20相比，抗倒伏基因型LS1和FM985表现出更强的根系锚定强度和更低的根系倒伏风险。这些特征主要归因于其更宽的根冠宽度、更大的投影根面积、更大的根角、更粗的支撑根以及根系在上层土壤中的更广泛的分布。但LS1根系骨架较大，不利于氮素吸收。土壤探索的代谢成本增加，导致根系伸长减少，根系深度变浅，从而限制了从土壤中获取氮。FM985表现出与XY335相当的氮吸收能力（略高于LS1），这主要是因为最外层冠根的生长角度更大和胚根的比根长度更大。随着植株密度的增加，LS1和FM985的根系性状降低幅度较大，但保持了比XY335和XD20更大的根冠结构，从而降低了倒伏风险。XY335和XD20在高植物密度下表现出更强的吸氮能力，这归因于根表面积、根体积和胚根根干物质以及底土中根干物质的增加。

结论

综上所述，保持优化的根冠结构，再加上增加胚根的表面积、体积和干物质以及底土中的根干物质，似乎是减少倒伏事件和增强氮吸收的更可行的方法。人口稠密。