Anatomia floral comparada e fruit set da espécie ginodioica Ocotea minarum (Lauraceae)

Abstract

Ocotea minarum (Lauraceae) is a gynodioecius species. Gynodioecy is a dimorphic reproductive system where plants with pistillate and perfect flowers coexist within the same population. Comparative floral anatomy studies provide insights into the origin, identity and homology of floral structures, playing a crucial role in systematics and the evolution of reproductive systems in Lauraceae. To understand the evolution of gynodioecy in Ocotea, we conducted a comparative floral anatomy study combined with morphological characters and fruit set data from perfect and pistillate flowers of Ocotea minarum. The collected material was stored in alcoholic fixative, selected and dehydrated in an alcohol series to be embebed in historesin, sectioned and stained. For the fruit set data, flowering and fruiting periods were monitored throughout the year, and branches from certain individuals were selected to count flowers and fruits. Hermaphrodite flowers are larger, with five vascular bundles in the tepals, one bundle in the stamens and three bundles in the pistil. Pistillate flowers are smaller, with three to five vascular bundles in the tepals, one bundle in the stamens and three bundles in the pistil. Histochemical tests for lipids, starch and polysaccharides were negative in the epidermis and parenchyma of the glands in both floral morphotypes, indicating that these structures do not produce nectar. Individuals with pistillate flowers produced up to thirty more fruits than individuals with hermaphrodite flowers. This suggests a resource optimization strategy, where pistillate flowers invest in ovule and ovary quality to produce many seeds and fruits, while perfect flowers focus on pollen production. Our results suggest that gynodioecy represents an intermediate evolutionary stage between cosexuality and dioecy.