THE ESSENTIALS OF PLANT TISSUE

Body of a flowering plant composed of complementary parts.

1. Shoot - above ground; carry on photosynthesis

2. Root - gather water and minerals and take them to the shoot

There are four main types of tissue found in angiosperms: meristem, ground, dermal, and vascular.

MERISTEMS

Plant growth is through tissue called meristems located mainly in the tips of shoots and roots. Meristems are like embryonic tissue that continues the entire life of the plant. They undergo cell division and are the source of all cells of a plant. These function the plant's entire life, since unlike an animal, it never stops growing.

There are three types of meristem.

1. Apical meristems - at tips of roots and shoots with small cells that divide and make these structures grow longer, an action called primary growth.

2. Lateral meristems - around the sides of the plant and grow outward so that the plant gets thicker, an action called secondary growth.

3. Intercalary meristems - found only in grass blades and cause the blade to regrow from the injured point. This explain the need to frequently cut grass and is why grass can live despite grazing of animals.

GROUND TISSUE

Ground tissue makes up most of the body of a plant, being found in the interior of roots, stems, and leaves. Among the functions are storage of food (example starch in a potato is stored in these cells), storage of fragrant substances (example oranges and lemons store citric acid in these cells which gives them their characteristic taste), photosynthesis (example cells in green leaves), and support (example the hulls of peanuts are composed of ground cells).

DERMAL TISSUE

Dermal tissue covers the plant and is normally one cell thick. In addition, a cuticle of a fatty material covers all exterior surfaces except roots and holds in water as well as helping keep out invading organisms.

How then do plants exchange water and gases with the atmosphere? There are openings in the leaves called stomata. These pores have guard cells that open and close them. The movement of water from leaves is called transpiration.

VASCULAR TISSUE

Vascular tissue is found in the veins of leaves and trunks of trees for examples. There are two main types of vascular tissue, xylem and phloem. Xylem transports water and phloem transports food (principally carbohydrates). This is the sap of a plant and may be sugary and thick (example sugar maple trees from which we refine maple syrup).