Plant biology

Plants are multicellular organisms that, unlike animals, make their own food from sunlight. Their cells differ from animal cells in having a rigid cell wall, a large central vacuole, and chloroplasts, the green organelles where food is produced. Many plant processes — the movement of water up a stem, the opening of pores in a leaf, the growth of a root toward gravity — happen slowly or invisibly, so animations and time-based simulations are useful for showing how they work.

The defining process of plant life is photosynthesis, in which chloroplasts use light energy to combine carbon dioxide and water into sugars, releasing oxygen as a by-product. This sugar is the plant's source of energy and building material. To support photosynthesis, plants must transport materials internally: water and dissolved minerals are drawn up from the roots through tissue called xylem, while the sugars made in the leaves are distributed to the rest of the plant through tissue called phloem, a movement driven partly by water loss from the leaves.

Flowering plants reproduce sexually through their flowers. Pollen carries the male sex cells to the female parts of a flower, and after fertilisation the flower develops into a fruit containing seeds, each able to grow into a new plant. Plants also respond to their surroundings through growth: hormones regulate processes such as bending toward light, root and shoot growth, flowering and the ripening of fruit. These responses let a stationary organism adjust to changing conditions.

Frequently asked questions

How do plants make their own food?

Through photosynthesis: chloroplasts use light energy to turn carbon dioxide and water into sugars, releasing oxygen as a by-product.

How do plants move water and sugars?

Water and minerals rise from the roots through xylem tissue, while sugars made in the leaves travel to the rest of the plant through phloem tissue.

How do flowering plants reproduce?

Pollen carries male cells to a flower's female parts; after fertilisation the flower forms a fruit containing seeds that can grow into new plants.