Worley AC, Baker AM, Thompson JD, Barrett SC
Int J Plant Sci. 2000 Jan;161(1):69-79. doi: 10.1086/314225.
Floral display (the size, number, and arrangement of open flowers) influences pollinator visitation to animal-pollinated plants and should be an important determinant of reproductive success. We examined variation in the size and number of open flowers in wild daffodils (Narcissus). Our analysis of published data on 45 taxa showed that flower number varied negatively with flower diameter among Narcissus species, which supports the widespread assumption that there is a trade-off between these traits. In contrast, field measurements indicated a positive relation between flower number and diameter within two populations of Narcissus dubius, and no relation was evident after we controlled for variation in bulb size. The discrepancy between inter- and intraspecific patterns may have occurred because variable resource levels obscure trade-offs when variation in flower size is low (e.g., within species). Size-related increases in floral tube length were half as great as corresponding increases in flower diameter, a result that is consistent with stronger stabilizing selection on tube length. Staggered flowering within N. dubius inflorescences limited the mean number of open flowers to <66% of total flower number, and slow expansion by later opening flowers resulted in significant differences in flower size throughout flowering. Although pollinators preferred large flowers, experimental reductions in flower diameter did not affect seed production. Our results illustrate how the relative importance of the factors influencing floral display can vary among levels of biological organization. Interspecific variation in flower size and number appeared to be constrained by allocation trade-offs, but intraspecific variation in both traits was more greatly influenced by plant resource status. Within plants, the size and number of open flowers reflected the relative age of individual flowers and floral longevity.
花展示（开放花朵的大小、数量和排列）会影响传粉者对动物传粉植物的访问，并且应该是繁殖成功的一个重要决定因素。我们研究了野生水仙（水仙属）开放花朵大小和数量的变化。我们对45个分类群已发表数据的分析表明，水仙属物种中花的数量与花直径呈负相关，这支持了普遍的假设，即这些性状之间存在权衡。相比之下，实地测量表明，在两个喇叭水仙种群中，花的数量与直径呈正相关，并且在我们控制了鳞茎大小的变化后，没有明显的相关性。种间和种内模式之间的差异可能是因为当花大小的变化较低时（例如在物种内），可变的资源水平掩盖了权衡。与大小相关的花管长度增加只有花直径相应增加的一半，这一结果与对花管长度更强的稳定选择一致。喇叭水仙花序内的交错开花将开放花朵的平均数量限制在总花数的<66%，后期开放花朵的缓慢扩展导致整个开花期花朵大小存在显著差异。尽管传粉者更喜欢大花，但实验性地减小花直径并没有影响种子产量。我们的结果说明了影响花展示的因素的相对重要性如何在生物组织水平之间变化。花大小和数量的种间变异似乎受到分配权衡的限制，但这两个性状的种内变异受植物资源状况的影响更大。在植物内部，开放花朵的大小和数量反映了单个花朵的相对年龄和花寿命。
