Abstract:
Lardizabalaceae is one of the core families in Ranunculales, and its unisexual flower has small greenish petals (so-called nectary leaves). However, the features of petal diversity, morphology and structure in Lardizabalaceae are still unclear, preventing the further research on the reproductive biology of this group. In this study, the petals of three genera in Lardizabalaceae were studied using light microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that petals underwent four key development stages, and the divergence occurred in stage 3 resulted in petal morphological differences. There were 5 types of epidermal cell in the studied petals, in which 3 types were secretory cells. The secretory tissue, consisting secretory epidermal cells and several layers of secretory parenchyma cells, located on tip of the petal. Vascular bundles were seen between the secretory parenchyma cells occasionally (Sinofranchetia), and there were abundant plastids, mitochondria, rough endoplasmic reticulum and plasmodesmata in the secretory epidermal cells. Nectar was released through numerous micro-channels on the outer cell walls of epidermal cells, the modified stomates and the ruptured cell walls. The ancestral character reconstruction in Lardizabalaceae showed that nectariferous petals may be the ancestral character of Lardizabalaceae (52.5%).
