Plant Tissue Systems

Plant tissues are grouped into three main systems:

• The ground tissue system is the most extensive. It makes up the bulk of the plant body.
• The vascular tissue system contains two kinds of conducting tissues that distribute water and solutes through the plant body.
• The dermal tissue system covers and protects the plant's surfaces.

Some tissues in these systems contain only one type of cell and are called simple. Others are complex, highly organized arrays of two or more types of cells.

This animation (Audio - Important) describes plant tissue systems.

Meristems

Meristems are specialized regions of tissue for plant growth.

Apical meristem (embryonic cells) at the tips of roots and shoots is responsible for growth and elongation. Growth originating at root and shoot tips is labeled primary growth. Descendants of some of these cells will develop into the specialized tissues of the elongating root and stem. Cells that form at apical meristems are either protoderm, ground meristem, or procambium.

Lateral meristems are responsible for the increase in diameter of roots and stems. This is called secondary growth. Vascular cambium and cork cambium are two kinds of lateral meristems.

Simple Tissues

Simple tissues are made up of only one type of cell and are called either parenchyma, collenchyma, or sclerenchyma.

Parenchyma is the most common tissue in ground tissue systems. It comprises most of a plant's soft primary growth. Cells are pliable, thin walled, and many sided. Its cells are metabolically active at maturity and retain the capacity to divide, as in wound healing. Various types of parenchyma participate in photosynthesis, storage, secretion, and other tasks. Mesophyll is a type of parenchyma that contains chloroplasts

Collenchyma cells are thickened and help strengthen the plant. Cells are specialized for support for primary tissues. The cells are elongated, with walls (especially corners) thickened with pectin. Pectin makes stems strong but pliable. Collenchyma cells are alive at maturity. The "strings" in celery are good examples of collenchyma.

Sclerenchyma supports and protects mature plant parts. It protects many seeds. Sclerenchyma cells have thick, lignified walls and are dead at maturity. Lignin is deposited in its cells where it anchors, waterproofs, and protects. There are two types of sclerenchyma, fibers and sclerids. Fibers are long, tapered cells. Sclereids are stubbier cells. Long tapered fibers flex and twist and therefore are useful in making rope. Thickened sclereids form nut shells, peach pits, and gritty fruits.

Complex Tissues

Complex tissues are composed of a mix of cell types and include xylem, phloem, and epidermis. Xylem and phloem are vascular tissues.

REVIEW: Soft, moist plant parts consist mostly of _____ cells.
Answer parenchyma