Plants - Groups : Embryophyte

The embryophytes are the most familiar group of plants, including trees, flowers, ferns, mosses, and various others. All are complex multicellular organisms with specialized reproductive organs and, with very few exceptions, they obtain their energy through photosynthesis, i.e. by absorbing light, and synthesize food from carbon dioxide. They may be distinguished from multicellular algae by having sterile tissue within the reproductive organs. Further, embryophytes are primarily adapted for life on land, although some are secondarily aquatic. Accordingly they are often called land plants.

Embryophytes developed from complex green algae during the Palaeozoic era. Their closest living relatives are the Charales or stoneworts. These algae undergo an alternation between haploid and diploid generations, respectively called gametophytes and sporophytes. In the first embryophytes, however, the sporophytes became very different in structure and function, remaining small and dependent on the parent for their entire brief life. Such plants are called bryophytes; they include three surviving groups:

    * Bryophyta (mosses)
    * Anthocerotophyta (hornworts)
    * Marchantiophyta (liverworts)

All bryophytes are relatively small and are usually confined to moist environments, relying on water to disperse their spores. Other plants better adapted to terrestrial conditions appeared during the Silurian, and during the Devonian they diversified and spread to many different land environments. These are called vascular plants or tracheophytes. They have vascular tissues or tracheids, which transport water throughout the body, and an outer layer or cuticle that resists desiccation. In most the sporophyte is the dominant individual, and develops true leaves, stems, and roots, while the gametophyte remains very small.

Many vascular plants still reproduce using spores, including the following extant groups:

    * Lycopodiophyta (clubmosses)
    * Equisetophyta (horsetails)
    * Psilotophyta (whisk ferns)
    * Ophioglossophyta (adders'-tongues and grape-ferns)
    * Pteridophyta (ferns)



 

source : hydroponicsearch