Approximately 350,000 species of plants make up the Kingdom Plantae. They include trees, shrubs, land plants, ferns, algae and moss. Flowering plants or land plants make up about 90 percent of the kingdom and are purposely grown for their aesthetic or nutritional value. All plants are beneficial to the environment and provide many uses for human and animal life. The parts of a plant work together to ensure the continuance of the species.
The parts of a plant can be divided into two main groups. The sexual reproductive parts are those parts involved in the production of the seeds of the plant. Such parts include the flowers, fruit and seeds. The vegetative parts of the plant include stems, leaves and roots. The vegetative parts of a plant can be used in asexual reproduction of the plant. Cuttings are an example of asexual reproduction.
The stem of the plant supports the buds and leaves of the plant. It also serves as a conduit for transporting water, minerals and sugars. The internal portion of the stem is made up of three major parts. The xylem vessel is used to transport water and minerals, while phloem tubes transport food. The cambium is the busy layer of tissue responsible for cell division and active growth. Stems can grow above the ground or below the ground, but must have buds or leaves present to be considered a stem.
Plant leaves generally consist of a stalk, called a petiole, and a blade (the lamina). In simple leaves, the lamina is in one piece. In compound leaves, several pieces of lamina are joined to one petiole. The leaf is supported away from the stem by the petiole.
The major role of plant leaves is to absorb sunlight for the manufacturing of plant sugars. This process is called photosynthesis and is very important for the production of plant food and energy. Photosynthesis also benefits human life and animal life as it removes carbon dioxide from the atmosphere and replaces it with oxygen.
Another role played by leaves is in the identifying of the varieties and species of horticultural plants. Many plant leaves have also been been found edible.
Plant roots have two major functions. They are responsible for the absorption and transportation of water and inorganic nutrients, and they serve as an anchor for the plant body. Roots often function as a storage unit for food and nutrients. In some plants, the roots may be used for propagation. The structure and growth of the plant root affects the size and vigor of the plant, itself. Enlarged roots represent the edible portion of such vegetable crops as the sweet potato, carrot and parsnip.
The flower is the showiest part of the plant and has the sole responsibility of sexual reproduction. Its fragrance and bright-colored petals are designed to attract bees and other pollinators. These pollinators transfer the pollen from the male stamen to the female stigma. Without pollination, the plant species could not continue. A complete flower consists of a stamen, pistil, petals and sepals. If any of these parts are missing, the flower is incomplete. If only the stamens and pistils are present, the flower is termed "perfect." If either one of these essential parts is missing, the flower is imperfect. Imperfect flowers need two individual flowers in order to pollinate and create seeds. Only pollinated flowers will develop into fruits.