Each part of a plant contributes to its growth and survival both an individual specimen and as a collective species. Plants have systems that perform complementary functions designed to support the life of the plant and produce seeds or execute other reproductive strategies, such as spores or runners or tubers.
Roots hold the plant in place, absorb water from the ground and transport it to the rest of the plant, store food and sometimes propagate new plants. The shallow primary root or a deep tap root branches into secondary roots covered with tiny root hairs and ending in a root cap. The root hairs absorb water and nutrients. The root cap protects the ends of the root and acts as a kind of drill bit to bore through the ground, allowing the roots to spread and increase the nutrient-gathering capacity of the plant.
The stem supports the leaves and flowers and serves as the primary transport for water and nutrients on the way to the leaves. The stem often forms a main trunk or stem and extends branches out into smaller horizontal extensions of the main stem from which the leaves grow. The main stem may branch into a secondary stem on some plants. Nodes from which leaves grow are spaced along the stem and branches. The space between the nodes is called the internode. Lateral buds may appear at the nodes. A main terminal bud forms at the end of the main stem. Secondary terminal buds are found at the ends of branches. Lateral buds tend to form leaves, while terminal buds often become flowers.
The blade of a leaf is the flat, extended and most obvious part of the leaf. The edge of the leaf is called the margin. The petiole is the stemlike connection between the leaf and branch. Visible on both sides of the blade are raised tube-like structures called veins that extend from the petiole onto the surface of the blade. The veins are vascular bundles that carry nutrients between the leaves and the body of the plant. The large central vein is called the midrib.
Flowers are divided into three sections: the perianth, the androceium and the gynoceium. The perianth is the nonreproductive part of the flower consisting of the corolla, or colored petals, and the calyx. The calyx is the green part of the flower formed by the sepals, which support the petal display. The androceium is the male reproductive part of the flower and includes the stamen--a pollen-carrying leaf that consists of the filament, which is a stalk-like projection, and the anther, a bag of pollen at the end of the filament. The gynoceium is female reproductive part of the flower consisting of the carpel, which, like the stamen, is a transformed leaf. At the base of the carpel is the ovary, an expanded structure holding the ovules to be fertilized. The style connects the ovary and the stigma, a structure at the top of the style that collects pollen. At the base of the flower is the receptacle, a saucer-like structure that supports the flower structure, and the peduncle, which links the flower to the stem.
The fruit and seed structure of a plant consists of the pericarp (fruit) and the seed itself. The pericarp is divided into three parts, the exocarp or skin which protects the fruit and seed, the mesocarp or flesh of the fruit and the endocarp which is an often hard covering which covers the seed itself.
Plants have two basic types of seeding strategies. Gymnosperms produce naked seeds in structures like pine cones; they generally don't produce flowers and are pollenated by the wind. Angiosperms produce flowers that develop into some sort of fruit with seeds and are pollenated by animals. The basic parts of a seed are included in two structures, the embryo and endosperm. The embryo is the embryonic plant. The radical is the part of the embryo that emerges first and becomes the main root. The plumule is the first leaf the plant will unfurl. The hypocotl is the bit between the radical and the plumule that will become the plant's stem. The endosperm is the food supply for plant in its early stages of germination. The endosperm is generally protected by the seed coat or testa, which protects the seed from harm.