Unequal stability of diferent parts in the fag blossom (Leguminosae) with notes on factors afecting variability of pentamerous pentacyclic angiosperm fowers

Abstract

Angiosperm flowers are subject to spontaneous fluctuations in their structure, so in the same individual plant normal and anomalous flowers may coexist. While extra or missing organs usually do not affect the efficiency of pollination in poly-symmetric flowers, such meristic changes may impair the interaction between floral parts in monosymmetric flowers, like in Leguminosae. This work aims to investigate the range of meristic changes in pentamerous pentacyclic flowers of Leguminosae (fag blossoms) and several other eudicot families. Both leguminous and non-leguminous flowers exhibit similar ranges of variation affecting one or several floral whorls, either adjacent or not. The most variable part of the flower is the androecium. In the papilionoid corolla, the most stable part is the adaxial petal (fag), while the most variable feature is the presence or absence of the inner adaxial (vexillary) stamen. This observation agrees with the fact that all petals except for adaxial, as well as vexillary stamen, are recurrently reduced in different leguminous lineages. Among factors potentially contributing to the floral stability, the most significant is inflorescence structure, as highly ramified cymose inflorescences exhibit a wider range of meristic changes in flowers.