Flowering plants

Flowering plants (Angiospermae) are a major group within the broader category of seed plants. Their defining features are that the reproductive organs lie within flowers, and that the seeds develop inside a closed structure called the carpel, which after maturation becomes a fruit that protects the seeds.

Angiosperms are the most diverse group of plants on land, comprising hundreds of thousands of species. They occur in varied habitats: tropical forests, deserts, freshwater, and even some marine environments. Most of the food humans obtain—grains, rice, legumes, vegetables, fruits—comes from flowering plants.

Structure of the flower

A flower typically has four concentric parts: sepals (protective structures around the unopened flower), petals (colored structures that attract pollinators), stamens (male structures that produce pollen), and the carpel or pistil (the female structure containing the ovule). Many flowers possess both male and female parts; others have them separated.

Pollination and fruit

Pollination begins when pollen reaches the tip of the carpel. A pollen tube then grows down to the ovule. Angiosperms undergo a process called double fertilization: one nucleus produces the embryo, the other produces a nutrient tissue that nourishes the developing seed. Subsequently, the carpel wall transforms into a fruit. Fruits aid seed dispersal through wind, water, or animals.

Classification

Historically, flowering plants were divided into two groups: monocots (with a single seed leaf, such as grasses, cereals, and palms) and dicots (with two seed leaves). Modern research based on genetic data revealed that dicots do not form a unified group; the term eudicots is now used, alongside several other groups that split off earlier, such as magnoliids.