玉米强弱势粒间机械脱粒破碎率的差异

Differences in mechanical threshing broken rate between superior and inferior maize grains

为明确机械脱粒时玉米强弱势粒间破碎率的差异及其影响因素,选用2个玉米品种,将玉米分强弱势粒分别机械脱粒,比较分析3次机械脱粒日期(8月9日、8月16日、8月23日)强弱势粒的含水率、百粒重、力学强度、淀粉粒形态和破碎率。结果表明,参试品种‘仲玉3号’在8月9日、8月16日和8月23日脱粒弱势粒的破碎率均高于强势粒,‘先玉1171’在8月16日和8月23日脱粒弱势粒的破碎率也均高于强势粒;不同机械脱粒日期强势粒的含水率和百粒重显著高于弱势粒,同时较弱势粒具有明显的力学强度优势。籽粒顶面压碎强度和胚部压碎强度与破碎率呈极显著和显著负相关(r=-0.46**,r=-0.34*),可更好地反映籽粒耐破碎能力;强势粒的角质胚乳淀粉粒大于弱势粒,强势粒的粉质胚乳淀粉粒主要呈多面体,弱势粒主要呈球体。强弱势粒含水率差异难以反映其耐破碎能力,粒重和力学强度差异是造成强弱势粒破碎率差异的重要原因。

High grain broken rate is the main limiting factor encountered when mechanically harvesting maize grains. Owing to different filling degrees, the structures of superior and inferior maize grains are different. Therefore, the objectives of this study were: 1) to explore the difference in mechanical threshing broken rate between superior and inferior grains and factors that influence this;2) to select a mechanical strength evaluation index with a high correlation with grain broken rate. Two maize varieties(‘Zhongyu 3’ and ‘Xianyu 1171’) were selected, and superior and inferior grains were mechanically threshed separately. Moisture content, 100-grain weight, mechanical strength, starch grain shape, and grain broken rate were compared and analyzed for the superior and inferior grains over three mechanical threshing dates(August 9, August 16, August 23). The results showed that the broken rate of inferior grians of ‘Zhongyu 3’ was higher than that of superior grains threshed on August 9, August 16, and August 23;and that the broken rate of ‘Xianyu 1171’ inferior grains was higher than that of superior grains on threshing dates August 16 and August 23. The moisture content and 100-grain weight of superior grains were significantly higher than those of inferior grains across different mechanical threshing dates. At the same time, the superior grains had an obvious mechanical strength advantage over the inferior grains. The results also showed that there were significant negative correlations between broken rate and facade crushing strength(r = -0.46**), broken rate and germ crushing strength(r = -0.34*), which could be used to better reflect the breaking resistance of grains. The horny endosperm starch granules of superior grains were larger than those of inferior grains, and the floury endosperm starch granules were mainly polyhedral in the superior grains but were mainly spheroid in inferior grains. The difference in moisture content between superior and inferior grains could not reliably reflect breaking resistance. Differences in grain weight and mechanical strength were the main factors behind differences in broken rate between superior and inferior grains. The present study highlighted the importance of the differences between superior and inferior grains in maize mechanical harvesting as well as the relationship between grain mechanical strength and breaking resistance.