Plants have the distinction of being the only organisms that utilize photosynthesis, a process that converts energy from the sun to chemical energy to produce their own food. A plant's anatomy is divided into two systems, roots and shoots, which are the keys to photosynthesis.
The root system is usually underground and is essential for anchoring a plant in the ground. The roots can be fibrous with many feathery strands or a single, long taproot. They may be a thick, rounded tuber reaching deep in the soil or a stem-like rhizome spreading horizontally near the surface for non-flowering plant reproduction. Water and mineral nutrients are absorbed from the soil through the root system and conducted to the rest of the plant. Roots are also used to store food.
The shoot system is the part of the plant that is above ground and includes the stems, leaves, buds, flowers and fruits. A node is the part of the stem from which branches or leaves grow. The petiole is the stalk that attaches a leaf to the stem. Chlorophyll, the pigment that gives a plant its color, is found in the shoot system and is essential for photosynthesis. The shoot system also conducts food and water throughout the plant and is responsible for reproduction and dispersal.
The root and shoot systems are made of tissue clusters of similar or dissimilar cells. Plants have three types of tissue: dermal, ground and vascular. Dermal tissue is usually a single layer of cells and acts as a skin, protecting the plant from water loss and fungal invasion. Ground tissue makes up the bulk of the plant and is responsible for photosynthesis, food storage and supporting the plant. Vascular tissue conducts food, water and minerals throughout the plant and plays a minor role in supporting the plant.
Plants have five types of cells: parenchyma cells, collenchyma cells, schlerenchyma cells, xylem cells and phloem cells. Parenchyma cells have thin, flexible cells walls, carry on the plant's metabolic processes and are found in dermal, ground and vascular tissues. Collenchyma cells are found in ground tissue and play an important role in supporting the plant. Schlerenchyma cells are found in ground and vascular tissue. Xylem cells are in the vascular tissue and are responsible for conducting water and ions throughout the plant. Phloem cells are conduits for food from the leaves to the rest of the plant and are found in vascular tissue.
Angiosperms, flowering plants, reproduce through flowers which are pollinated and produce viable seeds. Flowers have petals, sepals (the small leaves under the flower), pistils (female reproductive organs) and stamens (male reproductive organs). Some flowers have only female reproductive organs, some have only male reproductive organs, and some have both. Likewise, some plants have only female flowers; some have only male flowers; some have both. Both male and female organs are necessary for viable reproduction.