As for all animals, your body is made of four types of tissue: epidermal, muscle, nerve, and connective tissues. Plants, too, are built of tissues, but not surprisingly, their very different lifestyles derive from different kinds of tissues. All three types of plant cells are found in most plant tissues. Three major types of plant tissues are dermal, ground, and vascular tissues.
Dermal tissue covers the outside of a plant in a single layer of cells called the epidermis. You can think of the epidermis as the plant’s skin. It mediates most of the interactions between a plant and its environment. Epidermal cells secrete a waxy substance called cuticle, which coats, waterproofs, and protects the above-ground parts of plants. Cuticle helps prevent water loss, abrasions, infections, and damage from toxins.
This tissue includes several types of specialized cells. Pavement cells, large, irregularly shaped parenchymal cells which lack chloroplasts, make up the majority of the epidermis. Within the epidermis, thousands of pairs of bean-shaped schlerenchymal guard cells swell and shrink by osmosis to open and close stomata, tiny pores which control the exchange of oxygen and carbon dioxide gases and the release of water vapor. The lower surfaces of some leaves contain as many as 100,000 stomata per square centimeter.
The epidermis of Arabidopsis shows both pavement cells (A) and stomata made of sclerenchymal guard cells (B), which control water loss and gas exchange.
Ground tissue makes up much of the interior of a plant and carries out basic metabolic functions. Ground tissue in stems provides support and may store food or water. Ground tissues in roots may also store food.
Vascular tissue runs through the ground tissue inside a plant. Your body was able to grow from a single cell to perhaps 100 trillion cells because, 21 days after fertilization, a tiny heart began to pump blood throughout your tiny self – and it hasn’t stopped since. The blood it pumps carries water, oxygen and nutrients to each one of your trillions of cells, and removes CO2 and other wastes. Of course plants don’t have hearts, but they do have vessels that transport water, minerals, and nutrients through the plant. These vessels are the vascular tissue, and consist of xylem and phloem. Xylem and phloem are packaged together in bundles, as shown in Figure below.
- cuticle: Waxy, waterproof substance produced by epidermal cells of leaves, shoots, and other above-ground parts of plants; prevents damage and loss of water by evaporation.
- dermal tissue: Type of plant tissue that covers the outside of a plant in a single layer of cells called the epidermis.
- epidermis: In animals, outer layer of skin that consists mainly of epithelial cells and lacks nerve endings and blood vessels; in plants, outer layer of dermal tissue.
- ground tissue: Type of plant tissue making up most of the interior of the roots and stems of plants; carries out basic metabolic functions and provides support and storage.
- guard cells: Bean-shaped schlerenchymal cells in the epidermis; swell and shrink by osmosis to open and close stomata.
- phloem: Type of plant vascular tissue; transports food from photosynthetic cells to other parts of the plant.
- stomata (singular, stoma): Tiny pore in the epidermis of a plant leaf that controls transpiration and gas exchange with the air.
- vascular tissue: Type of tissue in plants that transports fluids through the plant; includes xylem and phloem.
- xylem: Type of plant vascular tissue; transports water and dissolved nutrients from roots to stems and leaves.
- The three types of plant cells are found in each of the major types of plant tissues: dermal, ground, and vascular tissues.
- Dermal tissue covers the outside of a plant in a single layer of cells called the epidermis. It mediates most of the interactions between a plant and its environment.
- Ground tissue makes up most of the interior of a plant. It carries out basic metabolic functions and stores food and water.
- Vascular tissue runs through the ground tissue inside a plant. It consists of bundles of xylem and phloem, which transport fluids throughout the plant.