Snow Allison A, Spira Timothy P
Department of Plant Biology, Ohio State University, 1735 Neil Avenue, Columbus, Ohio, 43210-1293.
University of Michigan Biological Station, Pellston, Michigan, 49769.
Evolution. 1996 Oct;50(5):1866-1870. doi: 10.1111/j.1558-5646.1996.tb03573.x.
The stigmas of animal-pollinated flowers often capture more pollen than is needed to fertilize all available ovules, and mixed-donor pollen loads are probably common. When this is the case, variation in average pollen-tube growth rates can potentially affect the number of seeds sired by a given plant. Despite considerable interest in effects of postpollination processes on male fitness, little is known about the extent of variation in pollen performance among plants from natural populations. To examine this question in Hibiscus moscheutos (rose mallow), we conducted mixed-donor hand-pollination experiments with 39 pollen donors bearing distinctive isozyme markers. Pairs of competing donors were compared on sets of 11 to 15 recipient plants per pair. These donors often differed in the proportions of seeds they sired, with the maximum deviation from an expected ratio of 50:50 being 68:32. Furthermore, three intensively studied plants exhibited consistent trends in relative pollen performance when each was tested against (1) the same three competitors, and (2) groups of 14 competitors chosen at random from the study population. In a separate experiment, we investigated the effects of salinity stress and high soil nutrients on pollen performance. These environmental factors had anticipated effects on leaf production, flower production, and petal length, but style length and (most importantly) the number of seeds sired relative to a standard pollen donor were not affected. In summary, this study provides the strongest evidence to date that pollen-tube competitive ability varies among coexisting plants and may be an important component of male fitness in plants.
虫媒花的柱头通常捕获的花粉量超过了使所有可用胚珠受精所需的量，混合供体的花粉负载可能很常见。在这种情况下，平均花粉管生长速率的变化可能会影响特定植物所产生种子的数量。尽管人们对授粉后过程对雄性适合度的影响非常感兴趣，但对于自然种群中植物之间花粉表现的变化程度却知之甚少。为了在芙蓉葵（玫瑰锦葵）中研究这个问题，我们对39个带有独特同工酶标记的花粉供体进行了混合供体人工授粉实验。每对竞争供体在每组11至15株受体植物上进行比较。这些供体所产生种子的比例常常不同，与预期的50:50比例的最大偏差为68:32。此外，当对三株经过深入研究的植物分别与（1）相同的三个竞争者，以及（2）从研究群体中随机选择的14个竞争者组成的组进行测试时，它们在相对花粉表现上呈现出一致的趋势。在另一个实验中，我们研究了盐胁迫和高土壤养分对花粉表现的影响。这些环境因素对叶片产量、花朵产量和花瓣长度产生了预期的影响，但花柱长度以及（最重要的是）相对于标准花粉供体所产生种子的数量并未受到影响。总之，这项研究提供了迄今为止最有力的证据，证明花粉管竞争能力在共存植物之间存在差异，并且可能是植物雄性适合度的一个重要组成部分。
