# Characterization of Fruit and Seed Development in the Genera Anacamptis and Serapias (Orchidaceae)

## TL;DR

This paper studies how fruits and seeds develop in two terrestrial orchid genera, focusing on structural changes and adaptations for survival and reproduction.

## Contribution

The study provides new insights into the rapid developmental processes of fruit and seed maturation in terrestrial orchids.

## Key findings

- A cavity of free air space forms around the embryo after fertilization, aiding seed buoyancy.
- Slanting ridges appear in seed testa cells during final development stages.
- Lignification in endocarp and testa cells protects ovules and embryos.

## Abstract

Developmental changes in the anatomy along with the maturation from ovaries to fruits and ovules to seeds were analyzed in two terrestrial species of the related genera Anacamptis and Serapias (Orchideae, Orchidaceae), using light and scanning electron microscopy. Our results show that the proliferation of the placentae and the differentiation of the ovules are well developed at the beginning of the anthesis. After fertilization of the ovules, a cavity of free air space is formed surrounding the embryo, contributing to the later buoyancy of seeds in both genera. At the last days of their development, the seeds showed slanting ridges in the periclinal walls of the testa cells. Raphides were observed in the valves, formed by packed needles composed of calcium oxalate, which contribute to avoiding herbivory. Lignification observed in the endocarp cells of the placenta and in the testa cells can be related to protecting the ovules and embryos. Terrestrial orchids need a faster maturation to ensure the efficacy of fertilization due to seasonal environmental changes in temperate areas, so developmental changes during the maturation of fruits and seeds take place in a shorter time than in epiphytic orchids.