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

VI. PLANT KINGDOM SYSTEM

LOWER SPORE PLANTS

GENERAL CHARACTERISTICS AND FEATURES

Class Charophyceae

It unites unicellular coccoid, sarcinoid (Chaetosphaeridium and Chlorokybus), and multicellular filamentous (Klebsormidium and Raphidonema) as well as heterotrichous Algae with parenchymatous-discoid (Coleochaete) or specific articulated-whorled Structure, in which the sexual process is a highly specialized oogamy (Chara, Nitella, etc.). Monad Cells (spermatozoids in Charales and zoospores with Gametes in other representatives) are covered On the surface of the Plasmalemma with submicroscopic organic scales and are characterized by an asymmetric Cytoskeleton with flagella on the ventral side near the apex of The Cell and directed sideways. They differ among other representatives of algae of the "green evolutionary line" in the Features of the ultracytological structure of flagellar "roots" and have a similar type of Organization of these structures, which is characteristic of the spermatozoids of higher plants. Cytokinesis occurs with the participation of a phragmoplast with The formation of a cell plate with pores and plasmodesmata in heterotrichous representatives (Charales), which are absent in coccoid, sarcinoid, and filamentous forms.

Mitosis is open or semi-open. Reproduction occurs sexually (oogamy, rarely heterogamy) and asexually (by Cell Division, thallus fragmentation, 2-flagellate zoospores, rarely akinetes), as well as vegetatively through gemmae (Charales).

In its biochemical composition, it is related to other classes of algae of the "green evolutionary line," not differing in pigment composition.

The Scope of the Class and its representation vary significantly among different authors, depending on each author's views on The Significance of individual diagnostic features and their consistency with the results of cytological and molecular-genetic studies of individual taxa. A modern and well-substantiated concept that differs significantly from the classical division of this class (which traditionally singled out only the order Charales) is a Classification scheme that distinguishes and includes four additional orders within Charophyceae: Chaetosphaeridales, Chlorokybales, Klebsormidiales, and Coleochaetales. This classification approach is based on data regarding the phylogenetic affinity of individual taxa and a complex of morphological and cytological features (the type of thallus structure and its organizational character, features of cytokinesis and reproduction, presence of a sexual process, etc.). Representatives of the extinct Chaetosphaeridales are considered the ancestral link of this plant group (as well as higher plants); they form a sister group to Charales and are linked through an unknown common ancestor.

Given the current syllabus and objectives of the course, we will consider only typical representatives: the order Charales and the genus Chara.