Cellules et tissus végétaux

Plant tissues carry out different functions such as growth, structural support, and nutrition. They are formed from specialized cells and are broadly categorized as either meristematic or permanent tissues.

Meristematic tissues are considered regions of embryonic tissue, capable of self-renewal and indefinite cell division. Scientists distinguish two main types of meristems, based on their location inside the plant.

Apical meristems are located at the tips of the roots and stems and enable elongation of these structures. Lateral meristems cause an increase in the thickness or girth of the growing plant, typically in woody plants.

Cells that comprise permanent tissues are terminally differentiated and can no longer divide. Depending on the function, these are classified as dermal, vascular, or ground tissue.

Dermal tissue is a complex, permanent tissue that is composed of various cell types. Dermal tissue promotes gas exchange and forms a protective plant surface. It is the first line of defense against pathogens and physical damage.

In non-woody plants, dermal tissue is found as a layer of tightly packed cells called the epidermis. In aerial parts of the plant, the epidermis is covered by the cuticle, a waxy coating that prevents water loss.

There are two types of vascular tissue: xylem and phloem. Water and minerals are transported in the xylem from roots to different parts of the plant. Phloem tissue conducts sugars from the site of photosynthesis to other parts of the plant.

Ground tissue is a simple tissue that is responsible for most metabolic functions in plants. It is the site of photosynthesis, provides structural support to the stems, and offers a supportive matrix to the vascular tissue.