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

IX. HIGHER SPORE PLANTS

Division Bryophytes (Bryophyta)

Bryophytes are Water/159.html">HIGHER SPORE PLANTS in which the gametophyte dominates over the sporophyte, and the sporophyte develops directly on the gametophyte. They represent a blind alley of evolution.

The vegetative body of bryological gametophytes is represented by a thallus, or in more advanced forms, by a stem, phylloids, and rhizoids. Mosses lack true roots and leaves. Their Cells show weak differentiation. Conducting elements appear only in the most advanced forms.

The gametophyte bears the Organs of sexual reproduction: archegonia and antheridia. Gametophytes can be monoecious (bisexual), dioecious (unisexual), or polygamous (both bisexual and unisexual). Spermatozoids are biflagellate. In the Presence of water, they reach the egg Cell and fertilize it within the archegonium. The zygote develops on the gametophyte into a sporophyte, which in bryophytes is referred to as a sporogonium.

In bryophytes, the sporogonium consists of a capsule, a seta, and a haustorium or FOOT embedded in the gametophytic tissue. Through the haustorium, the sporogonium absorbs water and nutrients from the gametophyte. The capsule of the sporogonium contains a sporangium with archesporial cells, which undergo Meiosis to produce haploid spores. Upon maturation, the capsule opens, and the spores are dispersed. Under favorable conditions, the spores germinate into a multicellular protonema of filamentous, thalloid, or spherical shape. Buds form on the protonema, giving rise to new gametophytes.

Bryophytes comprise over 25,000 species. They form the ground cover on soil, rocks, tree and shrub bark, as well as in water bodies and bogs.

The Division Bryophyta is divided into three classes: Anthocerotopsida, Marchantiopsida (liverworts), and Bryopsida (mosses). Among liverworts and mosses, there are numerous aquatic and wetland species.