Growth & Structure of Plants

There are three main parts of a plant: the root system, the stems and leaves. All of these functions work together to produce a full mature plant. The roots help absorb and maintain water, minerals and food. They not only seek out food and water for a plant, but also store nutrients as well. The stem system of a plant is vital for the overall structure and balance of a plant. It also serves the purpose of transporting food and water to the leaves above, which help produce photosynthesis. There are two types of leaves: simple and compound. Simple leaves are basically a leaf with one blade. A compound leaf is one of many blades, also known as leaflets.

The root system of a plant is a rather complex one. When a root system starts to grow, the cells are very fragile and can be damaged during growth. The result is a root cap that protects these fragile cells. In the middle of a root are two components that act as arteries throughout the plant; xylem and phloem. The Xylem transports water from the roots of the plant to the shoot system (branches, leaves, etc.). The Phloem transports food or minerals to any part of the plant that is need of nourishment. The xylem and phloem are not just present in roots, but in the stem system as well. There are two types of roots, Tap roots and Fibrous roots. A taproot system has one main or central root that has much smaller side branches. By concentrating their growth on into one axis, taproots are able to dig down deep into the soil, finding water where a more fibrous root system may not be able to. Some younger plants, such as trees, start their growth with one long taproot and develop a more fibrous system during its maturation process. Fibrous roots do not have a single large root; rather they have a system of roots of equal size in length and width. Fibrous roots are more spread out, gathering more water and minerals. They are also good for stability of young plants. Fibrous root systems, like those found in many grasses, can even help prevent soil erosion.

Whereas roots provide the anchorage of a plant, the stem is vital to a plants growth and stability. In the middle of the stem, you will find the xylem and the phloem, just like you would in the root system. The function of the xylem within the stem is to transport water and minerals to the leaves and living cells within it. The function of the phloem is to transport food produced by the leaves or take food from storage to any part of the plant that may be in need of nourishment. The taller the plant, the greater the turgor pressure is. “Cell turgor gives firmness to water-filled tissues. The difference between crisp and wilted lettuce leaves or celery petioles, illustrates the nature of turgid and non-turgid (flaccid) cells.”[1] Turgor pressure has great influence on the rigidity of a plant. The higher the turgor, the less flexible a plant will be. A stem not only transports food and water, but also provides much need support for the leaves which need to reach up high to gather sunlight needed for photosynthesis. Some stems are green and are able to produce food via photosynthesis. Plants such as cacti do not have any leaves, yet still carry out photosynthesis in the stem which carries the main photosynthetic organs.

As a plant grows taller, it normally grows wider as well. This process is called secondary growth. The cells that provide the extra girth are known as the lateral meristems. Within these meristems are secondary vascular tissues, which help transport food, water and minerals up and down the stem of the plant. When a tree is cut down, you will notice how a tree has many rings, known as growth rings. You can tell a lot about a trees life just by looking at its tree rings. You will notice if it’s been an ideal growing season, or one of harsh conditions depending upon the width of these rings. As the trees girth expands, the cells in the middle of the plant get stretched, expand and then destroyed by the tremendous pressure put upon it. Once the cells are compressed and have died, the dead cells then turn into a hard woody tissue called heartwood; gaining the much needed strength and rigidity necessary for the plants stability. In some plants such as trees, a protective layer is needed to protect the stem and the development of its secondary growth. Many new cells are created on the outer layer of the stem (meristems) which become impregnated with a waxy, waterproof material, then die off. These cells clump together to form what we know as bark, or cork cambium.

There are many types and shapes of leaves. Leaves are broken down into many categories such as lobing and division, shapes and margins, tips and basins, arrangements and the overall structure of the leaf itself. As stated above, there are two basic types of leaves: Simple and Compound. Like that of the roots and stems, the outside layer of a leaf is covered by the epidermal cell wall. The function of the epidermal wall is to create a protective layer on the outside,