Besides beautifying homes and landscapes, plants provide food to animals and humans. Each part of a plant has a specific and important job critical to the plant's survival. A plant's aerial (above-ground) portion includes the stem, leaves, flowers, fruits and seeds. The underground section of a plant includes roots and rhizomes, which are plant stems growing underneath the surface of the soil.
One of the most important jobs of the stem is carrying water and nutrients from the plant's roots to leaves and other parts of a plant. Food produced by the leaves then travels to other areas of the plant. Xylem cells move water through the stem, and the phloem cells move food. Another job of stems is providing support for the plant so leaves can reach needed sunlight for producing food.
Leaves are where food is made in green plants by a process called photosynthesis. In the presence of the green pigment called chlorophyll leaves capture light energy from sunlight to convert carbon dioxide from the air and water taken from the soil into sugar. This sugar is full of energy and serves as the food source for most plants. Besides making food for plants, leaves also exhale oxygen, which humans and other forms of life need to live.
The function of the flower is to produce seeds from which new plants grow. The female part of a flower is the pistil and is typically found in a flower's center. The pistil consists of the stigmas, ovary and style. The male parts (stamens), normally surrounding the pistil, are composed of the anther and filament. A flower's scents and its petals are used to lure bees and insects in pollination. Following pollination, petals fall off, with seeds developing in the flower's ovary.
A plant's fruit is the ripened ovary which contains seeds. After a plant is fertilized, the ovary swells, becoming either dry or fleshy to protect its developing seeds. Many vegetables such as tomatoes, beans and cucumbers are actually fruits in that they contain seeds which help in distributing more plants.
The seed of a plant contains the tiny embryo of a new plant. A ripened ovule, the seed has both an inner and an outer coat. Besides the embryo, it contains food-supplying energy and the materials needed for growth until the plant is able to grow its first leaves above the soil. A seed also contains a seed leaf (cotyledon), a plumule (shoot) and a radicle (root). For germination to occur, the seed first absorbs water and swells. Next the radicle emerges. Finally, the plumule appears.
The roots of a plant function like a straw, because they absorb water and minerals from soil, with tiny hairs sticking out of roots helping absorption. They provide support for plants by anchoring plants in soil so they don't topple over. Roots also store additional food, in the form of sugars and carbohydrates, for future use.