Stem lodging is a common problem in cereal crop production and a main constraint for grain yield improvement. The leaf sheath that surrounds and protects the hollow internodes of stem could provide the plants with a great physical support. However, this biomechanical function has been ignored for several decades in cereal crops. This study aimed to examine the biomechanical properties of basal stem internodes and lodging susceptibility of the whole plants with or without the clasping leaf sheath in wheat (Triticum aestivum L.) and oat (Avena sativa L.) among different genotypes and agronomic practices (including planting densities and nitrogen application rates). The main objective was to quantify the mechanical role of the leaf sheath in oat and wheat crops by a “safety factor” method. On average, the leaf sheath contributed 40%, 68% and 38% of the overall stem bending strength, flexural rigidity and safety factor, in oat, while it accounted for 11%, 24% and 10%, respectively, in wheat plants. The significant contribution of the leaf sheath is due to its vital role in enlarging the peripheral position (i.e., second moment of area) and stiffness (i.e., Young's modulus). The contribution ratios (%) were found to be higher in oat than in wheat plants, due to the greater mass density of leaf sheath and more proficient/prevailing stay‐green capability in oat genotypes. This study emphasizes the important mechanical role of clasping leaf sheath on stem internodes of cereals and indicates that the stay‐green trait of the leaf sheath can be exploited to design appropriate varieties with improved lodging resistance and great yield potential.

中文翻译：

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谷粒扣叶鞘的机械作用：来自燕麦和小麦植物的两个案例研究

茎倒伏是谷物作物生产中的常见问题，也是提高谷物产量的主要制约因素。围绕并保护茎中空节的叶鞘可以为植物提供强大的物理支撑。然而，这种生物力学功能在谷物作物中已经被忽略了几十年。这项研究的目的是检查小麦和燕麦（燕麦）上基茎节间的生物力学特性以及整株植株在有无叶鞘紧闭的情况下的倒伏敏感性。L.）在不同的基因型和农艺习惯（包括种植密度和氮肥施用量）之间。主要目的是通过“安全系数”方法量化燕麦和小麦作物中叶鞘的机械作用。在燕麦中，叶鞘平均占茎总弯曲强度，弯曲刚度和安全系数的40％，68％和38％，而在小麦植物中，叶鞘分别占11％，24％和10％。叶鞘的重要作用是由于其在扩大周围位置（即面积的第二矩）和刚度（即杨氏模量）中的重要作用。发现燕麦的贡献率（％）比小麦植物高，这是因为燕麦叶片基因型的叶鞘质量密度更高，并且具有更高的/保持生绿能力。