Plant Cells & Tissue Types

Primary Cell Wall

The outermost layer of a plant cell wall, made up of cellulose fibers and gelatinous polysaccharides, that defines the shape of the cell and withstands the turgor pressure of the plasma membrane.

Secondary Cell Wall

The thickened inner layer of a cell wall formed by certain plant cells as they mature and after they have stopped growing; contains lignin in water-conducting cells. Provide support or protection.

Plasmodesmata

Membrane-lines channels that traverse the cell walls, allowing the cytoplasm of one cell to connect directly with another. This connection ensures that the plasma membrane and cytoplasm of the two cells are continuous, enabling the transfer of ions, small molecules, and even some larger molecules. 

Vacuole

A large membrane-bound organelle that serves as a storage center for water, pigments, oils, and other substances.

Chloroplasts

An organelle that is responsible for converting sunlight into chemical energy through photosynthesis.

What are the THREE types of Tissue Systems found in plants?

Dermal, Ground, & Vascular

Dermal Tissue System

A complex tissue that is the outermost layer of cells that forms the outer layer of a plant (also referred to as the epidermis).

What is its FUNCTION?

In SHOOTS: protect the plant

In ROOTS: absorbing water and nutrients

Stoma

A microscopic pore or opening on the surface of a leaf or stem through which gas exchange occurs.

Guard Cells

Specialized, crescent-shaped cells forming the border of a plant stoma which change shape to open or close the pore.

Trichomes

A hairlike appendage that grows from epidermal cells in the shoot system of some plants. Their shape, size, and functional vary widely between plant species.

Ground Tissue System

This system consists of THREE distinct tissues:

1. Parenchyma

2. Collenchyma

3. Sclerenchyma

What is its FUNCTION?

Most photosynthesis and carbohydrate storage occurs in this system. Cells in this tissue are also responsible for the synthesis and storage of specialized products (colorful pigments, hormones, toxins for defense). Other cells may also play a large role in structural support.

Parenchyma Tissue

A simple tissue made up of parenchyma cells (relatively thin primary cell walls) filled with chloroplasts which make it the primary site of photosynthesis. In other organs, parenchyma cells store starch granules. 

Collenchyma Tissue

A simple tissue that is made up of Collenchyma cells, in which are characterized by an unevenly thickened primary cell wall and longer/thinner than parenchyma cells. These cells within the tissue provide flexible structural support for shoots.

Sclerenchyma Tissue

A simple tissue made up of Sclerenchyma cells, in which are characterized by the presence of the thick, rigid secondary cell wall and a relatively thin primary cell wall.

Two types of Sclerenchyma Cells present in this tissue:

1. Fibers: elongated cell that provide support to vascular tissue

2. Sclereids: short, variably shaped cells that protect

Vascular Tissue System

A complex tissue system that consists of two complex tissues (xylem & phloem) that functions in support and long-distance transport of water and dissolved nutrients in vascular plants.

Xylem: Transport of water and nutrients; structural support

Phloem: Transport of sugars amino acids, hormones, etc; structural support