angiosperm

Angiosperm, or flowering plant, refers to any member of the angiosperms, a major lineage of seed plants characterized by flowers and seeds enclosed within a fruit. The reproductive hallmark is double fertilization: one sperm fertilizes the egg to form a zygote, while another fuses with polar nuclei to create a triploid endosperm that provides nourishment to the developing embryo. This feature distinguishes angiosperms from gymnosperms.

Angiosperms are highly diverse, ranging from tiny herbs to large trees, and they occupy almost all terrestrial habitats. They are traditionally divided into two large clades, the monocots and the eudicots, though several basal lineages exist. Most produce flowers and fruits; the ovary develops into the fruit that protects and disseminates seeds. Leaf venation and stem anatomy vary, with monocots often showing parallel leaf veins and fibrous roots, while eudicots typically have netlike venation and often a taproot system. Xylem often includes vessel elements in many groups.

Pollination is accomplished by animals, wind, or both, making angiosperms a central component of many ecosystems. Seeds are dispersed by animals, gravity, wind, water, or mechanical means. Angiosperms form mutualistic relationships with pollinators and play a major role in human nutrition and horticulture, including many staple crops and ornamental plants.

Origin and diversification began in the early to mid-Cretaceous, with rapid radiation during the Cenozoic. Today, angiosperms are the most diverse and widespread group of land plants, sustaining numerous ecosystems and economies worldwide.