holobasidium

A holobasidium is a fungal structure that contains all of its basidiospores within a single cell. This is in contrast to the phragmobasidium, where the basidium is divided into multiple cells. Holobasidia are characteristic of the rust fungi (Pucciniales) and smut fungi (Ustilaginales), though they can also be found in some other fungal groups.

The holobasidium develops from a diploid basidiospore or hyphal cell. Following meiosis, the four resulting haploid nuclei are contained within the single cell of the holobasidium. Each nucleus then migrates to an apical projection of the basidium, which develops into a basidiospore. These basidiospores are typically borne on sterigmata, which are small stalks extending from the holobasidium.

The shape of a holobasidium can vary depending on the species, but it is often clavate (club-shaped) or ovate (egg-shaped). The cell wall of the holobasidium is usually smooth and hyaline (clear) or pigmented. The presence and morphology of the holobasidium are important taxonomic features used in the classification of fungi. Understanding the structure and function of the holobasidium is crucial for studying the life cycles and reproduction of these fungal groups.