Méndez Marcos, Traveset Anna
Department of Plant Ecology-Evolutionary Biology Centre, Uppsala University, Villavägen 14, 752 36 Uppsala, Sweden.
Oecologia. 2003 Sep;137(1):69-75. doi: 10.1007/s00442-003-1319-z. Epub 2003 Jul 3.
Gender expression in hermaphroditic plant species usually departs from strict equisexuality. Study of those departures can aid understanding of non hermaphroditic breeding systems and prevalence of hermaphroditism within angiosperms. Plant size is one of the most studied factors in relation to gender modification. We studied variation in gender expression in the hermaphroditic, mostly single-flowered Paeonia cambessedesii. We separately studied gender modification with increasing plant and flower size using a variety of currencies: number of ovules and stamens, dry mass, N and P. Flower size and number of floral structures (petals, stamens, carpels, and ovules) increased with plant size. Number of ovules increased more rapidly with increasing plant size than number of stamens, indicating a bias towards femaleness with increasing plant size. A similar pattern was found when regressing number of stamens and number of seeds against plant size. Number of floral structures increased with increasing flower mass, but no significant difference was found between stamens and ovules in their rate of increase. Thus, gender modification at plant level was not consistent with patterns at flower level. No differential allocation to stamens vs gynoecium, or sexual structures vs petals was found when using dry mass, N or P as currencies. However, a disproportionate increase in female allocation was found when number of structures was utilised as currency. Study of size-dependent gender expression will benefit from contrast of results obtained using several analysis levels and allocation currencies.
雌雄同体植物物种中的性别表达通常并不严格遵循完全两性同体。对这些偏离现象的研究有助于理解非雌雄同体的繁殖系统以及被子植物中雌雄同体的普遍程度。植物大小是与性别改变相关的研究最多的因素之一。我们研究了雌雄同体、大多单花的康氏芍药（Paeonia cambessedesii）的性别表达变化。我们使用多种衡量标准，分别研究了随着植株和花朵大小增加的性别改变：胚珠和雄蕊的数量、干质量、氮和磷。花朵大小以及花部结构（花瓣、雄蕊、心皮和胚珠）的数量随着植株大小增加。胚珠数量随着植株大小增加的速度比雄蕊数量更快，这表明随着植株大小增加，偏向雌性特征。当将雄蕊数量和种子数量对植株大小进行回归分析时，也发现了类似的模式。花部结构的数量随着花质量的增加而增加，但雄蕊和胚珠在增加速率上没有显著差异。因此，植株水平上的性别改变与花朵水平上的模式不一致。当使用干质量、氮或磷作为衡量标准时，未发现对雄蕊与雌蕊，或性器官与花瓣有差异分配。然而，当使用结构数量作为衡量标准时，发现雌性分配有不成比例的增加。使用多个分析水平和分配衡量标准所获得的结果进行对比，将有助于对大小依赖型性别表达的研究。
