Algae. 1992; 7(1): 33-43.

A summary of the Morphology of Chloroplasts and Flagellated Cells in the Phaeophyceae

Hiroshi Kawai

Department of Botany, Faculyt of Science

The morphologies of chloroplasts in vegetative cells and flagellated cells in the phaeophyceae are summarized. Phaeophycean chloroplasts are classified into 9 types based on the number and location of chloroplasts, presence and absence of pyrenoids and structure of pyrenoids. Among them, a single chloroplast in each cell is considered to be the most primitive condition in the Phaeophyceae, whereas several to many chloroplasts in each cell, without pyrenoids, are considered as the derived condition. Regarding the flagellated cells, the morphologies of zoospores are generally unigorm. Most zoospores have a longer anterior and a shorter posterior flagellum, a single chloroplast with a stigma and a flagellar swelling of the posterior flagellum. Zoospores of advanced laminariales lack stigmata and flagellar swellings. Presence and absence of pyrenoids in flagellated cells generally agree with the condition in vegetative cells. The morphology of gametes is more diverse. Some female gametes contain several chloroplasts. Most sperm of the Laminariales, Desmarestiales, Sporochnales and Fucales have a longer posterior flagellum. Some of them have several dispersed chloroplasts which are not associated with the flagellar bases. Mainly based on these characteristics, the order Scytosiphonales is here considered to have only distant phylogenetic relationship with Ectocarpales, Dictyosiphonales and Chordariales, and to contain the most primitive members of the Phaeophyceae.

Keywords : chloroplast, flagellum, Phaeophyceae, phylogeny, pyrenoid, swarmer