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Flowering plant

The meaning of «flowering plant»

The flowering plants, also known as Angiospermae (/ˌændʒioʊˈspɜːrmiː/),[5][6] or Magnoliophyta (/mæɡˌnoʊliˈɒfɪtə, -oʊfaɪtə/),[7] are the most diverse group of land plants, with 64 orders, 416 families, approximately 13,000 known genera and 300,000 known species.[8] Like gymnosperms, angiosperms are seed-producing plants. They are distinguished from gymnosperms by characteristics including flowers, endosperm within their seeds, and the production of fruits that contain the seeds. Etymologically, "angiosperm" literally means a plant that produces seeds within an enclosure; in other words, a fruiting plant. The term comes from the Greek words angeion ('case') and sperma ('seed').

The ancestors of flowering plants diverged from the common ancestor of all living gymnosperms during the Carboniferous, over 300 million years ago,[9] with the earliest record of angiosperm pollen appearing around 134 million years ago. The first remains of flowering plants are known from 125 million years ago. They diversified extensively during the Early Cretaceous, became widespread by 120 million years ago, and replaced conifers as the dominant trees from 60 to 100 million years ago.

Angiosperms differ from other seed plants in several ways, described in the table below. These distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.[a]

Angiosperm stems are made up of seven layers as shown on the right. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms. The vascular bundles of the stem are arranged such that the xylem and phloem form concentric rings.

In the dicotyledons, the bundles in the very young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles (interfascicular cambium), a complete ring is formed, and a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside. The soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.

Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They contain no cambium and once formed the stem increases in diameter only in exceptional cases.

The characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, and provide the most trustworthy external characteristics for establishing relationships among angiosperm species. The function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds.[citation needed] The floral apparatus may arise terminally on a shoot or from the axil of a leaf (where the petiole attaches to the stem).[citation needed] Occasionally, as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More typically, the flower-bearing portion of the plant is sharply distinguished from the foliage-bearing or vegetative portion, and forms a more or less elaborate branch-system called an inflorescence.

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