Seed

A seed is the part of a flowering plant that is produced after pollination and fertilization. It consists of a small plant (embryo) that is not yet developed, stored food to nourish the embryo as it begins to grow, and an outer coating for protection.

Seeds are the primary means by which flowering plants reproduce and disperse. Because seeds can withstand cold, drought, and prolonged dormancy, they allow plants to survive unfavorable growing conditions.

Parts of the seed

Three main parts exist. The embryo contains the primary root (radicle), the primary shoot, and the seed leaf (cotyledon). The stored food is found in the endosperm or in the cotyledons themselves, and typically consists of starch, fats, and proteins. The seed coat (testa) protects against water loss, disease, and damage.

Plant diversity

Plants with seeds are divided into two groups. Gymnosperms, such as coniferous trees, produce seeds on cone scales without enclosing them in fruit. Angiosperms (flowering plants) produce seeds enclosed in fruit, which aids in dispersal. Angiosperms are further divided into those with one cotyledon and those with two.

Dormancy and germination

Many seeds do not sprout immediately after falling from the parent plant. They enter dormancy (hurdo), which ensures they do not germinate at an unsuitable time. Germination conditions include water, appropriate temperature, and oxygen; some seeds require light, heat, or coat scarification before sprouting.

Dispersal

Seeds disperse by wind, water, animals, and explosive fruit rupture. Some have wings or hairs that catch the wind. Sweet fruits are eaten by birds and mammals, with seeds later deposited elsewhere in their droppings. Other types have hooks that cling to animal fur.

Importance in agriculture and food

Seeds are the foundation of global food supply. Wheat, rice, corn, sorghum, beans, and sesame are all seeds. Cooking oils are also derived from seeds. Farmers use seeds for cultivation; international seed banks preserve plant species to prevent extinction.