BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

VI. PLANT SYSTEMATICS

LOWER SPORE PLANTS

GENERAL CHARACTERISTICS AND FEATURES

Class Prasinophyceae

This Class unites unicellular, predominantly marine flagellated Algae as well as certain freshwater representatives with palmelloid and coccoid body structures, inhabiting various biotopes (plankton, benthos, periphyton). Fossil forms are known in deposits ranging from the Cambrian to the Miocene. The distinguishing features of algae in this class include the presence of a specific xanthophyll, prasinoxanthin, and naked Cells covered with submicroscopic organic scales. Some forms have been observed to possess a Cell wall. The cells are equipped with anywhere from one (Pedinomonas) to 8-16 flagella (Pyramimonas) emerging from an apical, or occasionally lateral, depression.

These scales sometimes cover the entire surface of the flagella and cells, and on the latter, they are arranged in layers (1-5 layers). Cytokinesis occurs through The formation of a furrow growing inward from the periphery to the center.

Vegetative Reproduction is carried out by Cell Division into two. Sexual reproduction in the form of isogamy is characteristic of certain representatives and occurs in very few species.

This is an important taxon for understanding the phylogeny of green algae. Representatives of this class are considered the ancestral, basal group of Chlorophyta, from whose various branches other classes of this division originated.