Vascular plant in the context of Moss

A leaf (pl.: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form the shoot system. In most leaves, the primary photosynthetic tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf, but in some species, including the mature foliage of Eucalyptus, palisade mesophyll is present on both sides and the leaves are said to be isobilateral. The leaf is an integral part of the stem system, and most leaves are flattened and have distinct upper (adaxial) and lower (abaxial) surfaces that differ in color, hairiness, the number of stomata (pores that intake and output gases), the amount and structure of epicuticular wax, and other features. Leaves are mostly green in color due to the presence of a compound called chlorophyll which is essential for photosynthesis as it absorbs light energy from the Sun. A leaf with lighter-colored or white patches or edges is called a variegated leaf.

Leaves vary in shape, size, texture and color, depending on the species The broad, flat leaves with complex venation of flowering plants are known as megaphylls and the species that bear them (the majority) as broad-leaved or megaphyllous plants, which also include acrogymnosperms and ferns. In the lycopods, with different evolutionary origins, the leaves are simple (with only a single vein) and are known as microphylls. Some leaves, such as bulb scales, are not above ground. In many aquatic species, the leaves are submerged in water. Succulent plants often have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines. Furthermore, several kinds of leaf-like structures found in vascular plants are not totally homologous with them. Examples include flattened plant stems called phylloclades and cladodes, and flattened leaf stems called phyllodes which differ from leaves both in their structure and origin. Some structures of non-vascular plants look and function much like leaves. Examples include the phyllids of mosses and liverworts.

In the study of the biological sciences, biocommunication is any specific type of communication within (intraspecific) or between (interspecific) species of plants, animals, fungi, protozoa and microorganisms. Communication means sign-mediated interactions following three levels of rules (syntactic, pragmatic and semantic). Signs in most cases are chemical molecules (semiochemicals), but also tactile, or as in animals also visual and auditive. Biocommunication of animals may include vocalizations (as between competing bird species), or pheromone production (as between various species of insects), chemical signals between plants and animals (as in tannin production used by vascular plants to warn away insects), and chemically mediated communication between plants and within plants.

Biocommunication of fungi demonstrates that mycelia communication integrates interspecific sign-mediated interactions between fungal organisms, soil bacteria and plant root cells without which plant nutrition could not be organized. Biocommunication of Ciliates identifies the various levels and motifs of communication in these unicellular eukaryotes. Biocommunication of Archaea represents key levels of sign-mediated interactions in the evolutionarily oldest akaryotes. Biocommunication of phages demonstrates that the most abundant living agents on this planet coordinate and organize by sign-mediated interactions. Biocommunication is the essential tool to coordinate behavior of various cell types of immune systems.

Aquatic plants, also referred to as hydrophytes, are vascular plants and non-vascular plants that have adapted to live in aquatic environments (saltwater or freshwater). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquatic animals such as fish, amphibians and aquatic insects, create substrate for benthic invertebrates, produce oxygen via photosynthesis, and serve as food for some herbivorous wildlife. Familiar examples of aquatic plants include waterlily, lotus, duckweeds, mosquito fern, floating heart, water milfoils, mare's tail, water lettuce, water hyacinth, and algae.

Aquatic plants require special adaptations for prolonged inundation in water, and for floating at the water surface. The most common adaptation is the presence of lightweight internal packing cells, aerenchyma, but floating leaves and finely dissected leaves are also common. Aquatic plants only thrive in water or in soil that is frequently saturated, and are therefore a common component of swamps and marshlands.

The Phanerozoic is the current and the latest of the four geologic eons in the Earth's geologic time scale, covering the time period from 542 million years ago to the present. It is the eon during which abundant animal and plant life has proliferated, diversified and colonized various niches on the Earth's surface, beginning with the Cambrian period when animals first developed hard shells that can be clearly preserved in the fossil record. The time before the Phanerozoic, collectively called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons.

The time span of the Phanerozoic starts with the sudden appearance of fossilised evidence of a number of animal phyla; the evolution of those phyla into diverse forms; the evolution of plants; the evolution of fish, arthropods and molluscs; the terrestrial colonization and evolution of insects, chelicerates, myriapods and tetrapods; and the development of modern flora dominated by vascular plants. During this time span, tectonic forces which move the continents had collected them into a single landmass known as Pangaea (the most recent supercontinent), which then separated into the current continental landmasses.

Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mineral-rich waters, such as chalybeate springs. Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/sleet and graupel, and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams, as well as groundwater contained in aquifers, subterranean rivers and lakes.

Water is critical to the survival of all living organisms. Many organisms can thrive on salt water, but the great majority of vascular plants and most insects, amphibians, reptiles, mammals and birds need fresh water to survive.

The Silurian-Devonian Terrestrial Revolution, also known as the Devonian Plant Explosion (DePE) and the Devonian explosion, was a period of rapid colonization, diversification and radiation of land plants (particularly vascular plants) and fungi (especially dikaryans) on dry lands that occurred 428 to 359 million years ago (Mya) during the Silurian and Devonian periods, with the most critical phase occurring during the Late Silurian and Early Devonian.

This diversification of terrestrial photosynthetic florae had vast impacts on the biotic composition of the Earth's surface, especially upon the Earth's atmosphere by oxygenation and carbon fixation. Their roots also eroded into the rocks, creating a layer of water-holding and mineral/organic matter-rich soil on top of Earth's crust known as the pedosphere, and significantly altering the chemistry of Earth's lithosphere and hydrosphere. The floral activities following the Silurian-Devonian plant revolution also exerted significant influences on changes in the water cycle and global climate, as well as driving the biosphere by creating diverse layers of vegetations that provide both sustenance and refuge for both upland and wetland habitats, paving the way for all terrestrial and aquatic biomes that would follow.

The Devonian (/dəˈvoʊni.ən, dɛ-/ də-VOH-nee-ən, deh-) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at 419.62 million years ago (Ma), to the beginning of the succeeding Carboniferous period at 358.86 Ma. It is the fourth period of both the Paleozoic and the Phanerozoic. It is named after Devon, South West England, where rocks from this period were first studied.

The first significant evolutionary radiation of life on land occurred during the Devonian, as free-sporing land plants (pteridophytes) began to spread across dry land, forming extensive coal forests which covered the continents. By the middle of the Devonian, several groups of vascular plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants (pteridospermatophytes) appeared. This rapid evolution and colonization process, which had begun during the Silurian, is known as the Silurian-Devonian Terrestrial Revolution. The earliest land animals, predominantly arthropods such as myriapods, arachnids and hexapods, also became well-established early in this period, after beginning their colonization of land at least from the Ordovician Period.

The species–area relationship or species–area curve describes the relationship between the area of a habitat, or of part of a habitat, and the number of species found within that area. Larger areas tend to contain larger numbers of species, and empirically, the relative numbers seem to follow systematic mathematical relationships. The species–area relationship is usually constructed for a single type of organism, such as all vascular plants or all species of a specific trophic level within a particular site. It is rarely if ever, constructed for all types of organisms if simply because of the prodigious data requirements. It is related but not identical to the species discovery curve.

Ecologists have proposed a wide range of factors determining the slope and elevation of the species–area relationship. These factors include the relative balance between immigration and extinction, rate and magnitude of disturbance on small vs. large areas, predator-prey dynamics, and clustering of individuals of the same species as a result of dispersal limitation or habitat heterogeneity. The species–area relationship has been reputed to follow from the 2nd law of thermodynamics. In contrast to these "mechanistic" explanations, others assert the need to test whether the pattern is simply the result of a random sampling process. Species–area relationships are often evaluated in conservation science in order to predict extinction rates in the case of habitat loss and habitat fragmentation.

Antarctic flora are a distinct community of vascular plants which evolved millions of years ago on the supercontinent of Gondwana. In 2025, species of Antarctica flora reside on several now separated areas of the Southern Hemisphere, including southern South America, southernmost Africa, New Zealand, Australia, and New Caledonia. Joseph Dalton Hooker (1817 – 1911) was the first to notice similarities in the flora and speculated that Antarctica had served as either a source or a transitional point, and that land masses now separated might formerly have been adjacent.

Based on the similarities in their flora, botanist Ronald D'Oyley Good identified a separate Antarctic Floristic Kingdom that included southern South America, New Zealand, and some southern island groups. In addition, Australia was determined to be its own floristic kingdom because of the influx of tropical Eurasian flora that had mostly supplanted the Antarctic flora and included New Guinea and New Caledonia in the Paleotropical floristic kingdom.

Botany, also called phytology or plant science, is the branch of natural science and biology that studies plants, especially their anatomy, taxonomy, and ecology. A botanist or plant scientist is a scientist who specialises in this field. "Plant" and "botany" may be defined more narrowly to include only land plants and their study, which is also known as phytology. Phytologists or botanists (in the strict sense) study approximately 410,000 species of land plants, including some 391,000 species of vascular plants (of which approximately 369,000 are flowering plants) and approximately 20,000 bryophytes.

Botany originated as prehistoric herbalism to identify and later cultivate plants that were edible, poisonous, and medicinal, making it one of the first endeavours of human investigation. Medieval physic gardens, often attached to monasteries, contained plants that possibly had medicinal benefits. They were forerunners of the first botanical gardens attached to universities, founded from the 1540s onwards. One of the earliest was the Padua botanical garden. These gardens facilitated the academic study of plants. Efforts to catalogue and describe their collections were the beginnings of plant taxonomy and led in 1753 to the binomial system of nomenclature of Carl Linnaeus that remains in use to this day for the naming of all biological species.

A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaves, flowers and fruits, transports water and dissolved substances between the roots and the shoots in the xylem and phloem, engages in photosynthesis, stores nutrients, and produces new living tissue. The stem can also be called the culm, halm, haulm, stalk, or thyrsus.

The stem is normally divided into nodes and internodes:

Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which in some cases can store starch. In eudicotyledons, pith is located in the center of the stem. In monocotyledons, it extends only into roots. The pith is encircled by a ring of xylem; the xylem, in turn, is encircled by a ring of phloem.

While new pith growth is usually white or pale in color, as the tissue ages it commonly darkens to a deeper brown color. In trees pith is generally present in young growth, but in the trunk and older branches the pith often gets replaced – in great part – by xylem. In some plants, the pith in the middle of the stem may dry out and disintegrate, resulting in a hollow stem. A few plants, such as walnuts, have distinctive chambered pith with numerous short cavities. The cells in the peripheral parts of the pith may, in some plants, develop to be different from cells in the rest of the pith. This layer of cells is then called the perimedullary region of the pithamus. An example of this can be observed in Hedera helix, a species of ivy.

Xylem is one of the two types of transport tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts of the plants such as stems and leaves, but it also transports nutrients. The word xylem is derived from the Ancient Greek word ξύλον (xúlon), meaning "wood"; the best-known xylem tissue is wood, though it is found throughout a plant. The term was introduced by Carl Nägeli in 1858.

The euphyllophytes are a clade of plants within the tracheophytes (the vascular plants). The group may be treated as an unranked clade, a division under the name Euphyllophyta or a subdivision under the name Euphyllophytina. The euphyllophytes are characterized by the possession of true leaves ("megaphylls"), and comprise one of two major lineages of extant vascular plants. As shown in the cladogram below, the euphyllophytes have a sister relationship to the lycopodiophytes or lycopsids. Unlike the lycopodiophytes, which consist of relatively few presently living or extant taxa, the euphyllophytes comprise the vast majority of vascular plant lineages that have evolved since both groups shared a common ancestor more than 400 million years ago. The euphyllophytes consist of two lineages, the spermatophytes or seed plants such as flowering plants (angiosperms) and gymnosperms (conifers and related groups), and the Polypodiophytes or ferns, as well as a number of extinct fossil groups.

The division of the extant tracheophytes into three monophyletic lineages is supported in multiple molecular studies. Other researchers argue that phylogenies based solely on molecular data without the inclusion of carefully evaluated fossil data based on whole plant reconstructions, do not necessarily completely and accurately resolve the evolutionary history of groups like the euphyllophytes.

The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (land plants with vascular tissues such as xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from non-vascular plants (mosses, hornworts and liverworts) by having specialized transport bundles that conduct water and nutrients from and to the roots, as well as life cycles in which the branched sporophyte is the dominant phase.

Ferns have complex leaves called megaphylls that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns that produce coiled fiddleheads that uncoil and expand into fronds. The group includes about 10,560 known extant species. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate (Polypodiidae) and eusporangiate ferns, the latter group including horsetails, whisk ferns, marattioid ferns and ophioglossoid ferns.

Lycopodiopsida is a class of vascular plants also known as lycopsids, lycopods, or lycophytes. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching stems bearing simple leaves called microphylls and reproduce by means of spores borne in sporangia on the sides of the stems at the bases of the leaves. Although living species are small, during the Carboniferous, extinct tree-like forms (Lepidodendrales) formed huge forests that dominated the landscape and contributed to coal deposits.

The nomenclature and classification of plants with microphylls varies substantially among authors. A consensus classification for extant (living) species was produced in 2016 by the Pteridophyte Phylogeny Group (PPG I), which places them all in the class Lycopodiopsida, which includes the classes Isoetopsida and Selaginellopsida used in other systems. (See Table 2.) Alternative classification systems have used ranks from division (phylum) to subclass. In the PPG I system, the class is divided into three orders, Lycopodiales, Isoetales and Selaginellales.