Lehmann Naida L, Sattler Rolf
Biology Department, McGill University, 1205 Avenue Docteur Penfield, Montreal, Quebec, Canada, H3A 1B1.
Am J Bot. 1992 Oct;79(10):1145-1157. doi: 10.1002/j.1537-2197.1992.tb13710.x.
About two-thirds of the more than 100 genera in the Araceae lack tepals and their absence is considered derived. Unlike most of these atepalate genera, Calla palustris has about twice as many stamens per flower. Using epi-illumination microscopy, we studied floral development in Calla to see if the supernumerary stamens form in positions corresponding to tepal positions in perigonate Araceae. If so, this would be an example of homeosis-in this case, the replacement of tepals with stamens-in the evolution of this genus. We found the positions of stamen primordia in many floral buds too irregular to conclude that they replace tepals positionally. However, in more regular floral buds the first formed stamens do form in what correspond to tepal sites in related genera. If the immediate ancestor to Calla had tepals, as is generally assumed, stamen positions in the more regular flowers, at least, support a homeotic interpretation. There is no evidence that the supernumerary stamens arise by dédoublement, but since morphogenesis in Calla is only partly comparable to other aroids, and the phylogeny in the family is not well understood, further studies are needed to resolve the interpretation of the flower in Calla. With regard to systematics and evolution, the absence of tepals in Calla may not be homologous with atepaly in other members of the family, as has been assumed for the past century.
天南星科100多个属中约三分之二没有花被片，其缺失被认为是衍生特征。与大多数这些无花被片的属不同，水芋每朵花的雄蕊数量大约是其他属的两倍。利用落射荧光显微镜，我们研究了水芋的花发育过程，以观察额外的雄蕊是否在与具花被天南星科植物花被片位置相对应的位置形成。如果是这样，这将是一个同源异型的例子——在这种情况下，是花被片被雄蕊取代——在这个属的进化过程中。我们发现许多花芽中雄蕊原基的位置过于不规则，无法得出它们在位置上取代花被片的结论。然而，在更规则的花芽中，最早形成的雄蕊确实在与相关属花被片位置相对应的位置形成。如果像通常所认为的那样，水芋的直接祖先有花被片，那么至少在更规则的花中，雄蕊的位置支持同源异型的解释。没有证据表明额外的雄蕊是通过加倍产生的，但由于水芋的形态发生仅部分与其他天南星科植物可比，而且该科的系统发育尚未完全了解，需要进一步研究来解决对水芋花的解释问题。关于系统分类和进化，水芋中花被片的缺失可能与该科其他成员的无花被现象不同源，而在过去的一个世纪里一直是这样假设的。
