Embryophyte

The embryophytes () are plants of the cladeEmbryophyta (), also known as Plantae sensu strictissimo (, "plant in the strictest sense") or land plants. They are complex multicellulareukaryotes with haplodiplontic life cycles. All have specialized reproductive organs called sporangia, and reproduce sexually via alternation of generations using spores or seeds. The name "embryophyte" derives from their innovative characteristic of nurturing the embryonicsporophytes within the tissues of the parent gametophytes during the early stages of multicellular development. They are the dominant group of autotrophs that make up the vegetation on Earth's terrestrial and wetlandecosystems, and represent the quintessential concept of "plants" most familiar to the common knowledge. The study of embryophytes is called phytology.

Embryophytes consist of the relatively species-poor non-vascular plants and the much more species-rich vascular plants (tracheophytes). The former are soft-bodied groundcovers that include three divisions of bryophytes, namely Bryophyta (mosses), Marchantiophyta (liverworts) and Anthocerotophyta (hornworts); while the latter are vertical-growing "higher plants" with lignifiedstem, absorptive roots and stomatousleaves, which include all extantpolysporangiates such as lycophytes (clubmosses, firmosses, spikemosses and quillworts), polypodiophytes (ferns), gymnosperms (conifers, cycads, gnetophytes and gingko) and angiosperms (flowering plants). Since their boom during the mid/late Cretaceous, angiosperms have been the dominant group of embryophytes.

Embryophytes are predominantly a terrestrial chloroplastidian clade that shared a common ancestry with freshwatergreen algae, having emerged within the Phragmoplastophyta clade of charophyte algae as a sister clade of Charophyceae, Coleochaetophyceae and Zygnematophyceae. They are informally called "land plants" because they have evolved to thrive primarily in the drier environment of upland areas above the high water marks (although some members having evolved secondarily to live once again in semiaquatic/aquatic habitats), while the closely related green algae are primarily aquatic and depend heavily on waterbodies to thrive.

With very few exceptions, embryophytes are photoautotrophic and obtain metabolicbiological energy by photosynthesis, using chlorophyll a and b to harvest light energy from sunlight for carbon fixation in order to synthesize carbohydrates, while releasing oxygen as a byproduct. This primary production is the foundation of terrestrial food webs, where biomass and energy are introduced into the food chain via herbivory and detritivory.

The proliferation of land plants also had profound impacts on the Earth's oxygen cycle, carbon cycle, water cycle and climate variation as well as significant (sometimes permanent) alterations to the Earth's crust (creating an organic pedosphere by eroding the lithosphere), surface hydrology and hydrochemistry, since the land proliferation of plants during the mid-Paleozoic. There was a well-defined, stepwise oxygenation of Earth's atmosphere from about 2-11% atm during the Cambrian to mid-Ordovician and around 13% atm during early Silurian, to near modern-day levels (1 atm, about 21% mole fraction) in the Devonian and a peak of over 1.6 atm (around 35% mole fraction) during the late Carboniferous and most of the Permian periods, coinciding with (and likely directly caused by) the progressive radiation and terrestrial dispersal of embryophytes (especially vascular plants).

The carbon sequestration by land plants, particularly by the expansive Carboniferous coal forests, were responsible for the Late Paleozoic icehouse and also the proven reserves of coal and coal seam gas that have been important to humanity's energy economy since the Industrial Revolution.