花粉的时序呈现是指植物花药按一定次序释放花粉的现象, 被认为是对传粉者访问频率的一种适应。在传粉者充足的环境中, 植物通过限制花粉1次被移出的数量, 使花粉供体能作为多个父本, 从而提高雄性适合度。该文从开花习性、花部特征、传粉者及繁育系统等方面对早春短命植物黑鳞顶冰花(Gagea nigra)的花粉呈现时序及其适应性进行研究, 结果表明, 黑鳞顶冰花单花期约5-7天; 白天开放, 晚上闭合, 花药次序开裂, 呈拉链式散粉, 散粉期4-6天。黑鳞顶冰花以异交为主, 部分自交亲和。蝇类和食蚜蝇为主要传粉者, 访花频率为(0.141±0.078) flower∙h^-1。在雄蕊的时序散粉过程中, 雌蕊持续生长, 经历了从低于雄蕊到等高、再到高于雄蕊阶段。在等高阶段, 单花早晚的开闭, 使得雌雄蕊紧靠在一起, 促成了自动自花授粉。在传粉者缺乏的环境中, 黑鳞顶冰花的花粉时序呈现延长了散粉期, 在等待传粉者和分摊风险方面具重要作用。这种花粉渐次呈现的策略, 在新疆的早春开花植物中可能广泛存在。

Gradual pollen presentation is an adaptive strategy in flowering plants that limits pollen removal with high pollinator visitation rate. High visitation rates may favor plants presenting pollen gradually in many small doses and potentially enhance male reproductive success given that pollen grains could be donated to more different individuals. Here we studied the pollen presentation schedule and pollination adaptation of an early spring ephemeral plant, Gagea nigra, by investigating flower characteristics, pollinators and breeding systems in a natural population in Xinjiang Province, northwestern China. (1) The flowering period of single flowers was about 5 to 7 days; flowers open during the day and close at night. The anthers release pollen in the sequence of one by one and split longitudinally like a zipper, lasting 4-6 days. (2) The breeding system of the species was mainly outcrossing and partial selfing. Flies and hoverflies were the main pollinators, with mean visitation rate was 0.141±0.078 times per flower per hour. (3) During pollen presentation, the pistils continued to grow. Thus, the position of stigmas experienced three stages: below stamens, as high as stamens and higher than stamens. In the middle stage, with stamens and stigma at a similar height, the opening and closing of the single flowers during the day and night push the stamens and the stigma closely, thereby facilitating automatic self-pollination. (4) Under a scarcity of pollinators, the gradual pollen presentation in G. nigra extended the period of pollen release, elongating the time for pollinator visits that may reduce the risk of pollination failure, instead of an adaptation to abundant pollinators. Such a gradual pollen presentation strategy in terms of waiting for pollinators and risk of spreading may be widespread in many early spring flowering plants in Xinjiang.