Abstract: In order to explore the rules related to the process of spike differentiation in switchgrass,the lowland cultivar ‘Alamo’ was observed periodically by stereomicroscope during the development stages and their corresponding plant morphology were recorded. The results showed that spike differentiation in switchgrass was a slow-fast-slow process,which could be divided into 9 consecutive stages:sputum differentiation stage,primordium differentiation stage,spikelet differentiation stage,florets primordium differentiation stage,the stamen primordium differentiation stage,the drug septum formation period,the anther quadrant,the anther elongation period,and the pinnate stigma formation period,each period has a corresponding plant appearance morphology for discriminating the differentiation process. The spike differentiation in switchgrass took about 3 months when the plant developed from jointing stage to blooming stage. The florets of inflorescence bloomed from up to down,and the flowering period can reach 3~4 weeks.

Key words: Switchgrass, Spike differentiation, Plant morphology

摘要： 为探索柳枝稷（Panicum virgatum）幼穗分化过程与规律，以柳枝稷低地型品种"Alamo"为材料，对其幼穗分化过程进行显微观察并记录对应大田植株形态。结果发现：柳枝稷幼穗分化是一个慢-快-慢的过程，可分为9个连续的时期：苞原基分化期、枝梗原基分化期、小穗分化期、小花原基分化期、雌雄蕊原基分化期、药隔形成期、花药四分期、花药伸长期、羽状柱头形成期，每个时期均具有与之对应的植株外观形态以供判别分化进程。柳枝稷幼穗分化起始至分化完全历时约3个月，植株历经拔节、孕穗、抽穗而开花，花序从上到下依次开花，花期可达3~4周。

关键词: 柳枝稷, 幼穗分化, 植株形态