Algae. 2000; 15(4): 195-200.

Developmental Aspects of Tetrasporogenesis and Tetraspore Release in Dictyopteris australis (Sonder) Asdensay (Dictyotales, Phaeophyta)

Gunwant Bhamrah, Inderdeep Kaur

The plants of Dictyopteris australis (Sonder) Askensay are large, ribbon-like, dichotomously branched with a distinct midrib. The wing portion of the thallus is 2 or 3 celled thick and the midrib is about 5 celled thick. The deflexed lines of hairs borne on both surfaces of the thallus show tetrasporangia at various stages of development. Tetrasporangia are partially embedded and possess at maturity, a three layered wall with varying amounts of alginic acid and sulphated polysaccharides. The tetrasporangial cytoplasm shows abundant physodes, sulphated polysaccharides and vacuoles of various shapes and sizes. A reduction division results in the formation of tetraspores which are released by a highly coordinated mechanism. The outer layer of the tetrasporangium ruptures and the middle layer forms a stalk, temporarily holding the released tetraspore mass to the parent thallus. The tetraspores which are initially enclosed in middle and inner layer are later set free. The older thalli also show the formation of vegetative plants that remain attached to the parent thallus by means of branched rhizoids.