Plant Structure, Growth, and Development

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Tissue System: Each plant organ has: * dermal * vascular and * ground tissues

Dermal

tissue

Ground

tissue

Vascular

tissue

Slide 21

In nonwoody plants, the dermal tissue system consists of the epidermis.

A waxy coating called the cuticle helps prevent water loss from the epidermis.

In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots.

Trichomes are outgrowths of the shoot epidermis and can help with insect defense.

Slide 22

The vascular tissue system carries out long-distance transport of materials between roots and shoots.

Xylem conveys water and dissolved minerals upward from roots into the shoots.

Phloem transports organic nutrients from where they are made to where they are needed.

Slide 23

Tissues that are neither dermal nor vascular are the ground tissue system.

Ground tissue internal to the vascular tissue is pith; ground tissue external to the vascular tissue is cortex. Both have plastids for storage.

Ground tissue includes cells specialized for storage, photosynthesis, and support.

Slide 24

Common Types of Plant Cells - are specialized of cells in structure and function.

Some major types of plant cells:

Parenchyma - ground: thin flexible cell walls: photosynthesis, storage.

Collenchyma - ground: thicker cell walls for flexible support.

Sclerenchyma - ground: thick secondary cell walls reinforced with lignin for rigid, sturdy support.

Xylem - vascular: water-conducting cells.

Phloem - vascular: sugar-conducting cells.

Slide 25

Parenchyma cells in Elodea leaf,

with chloroplasts (LM)

60 µm

Slide 26

Sclerenchyma Cells

Sclerenchyma cells are rigid because of thick secondary walls strengthened with lignin.

They are dead at functional maturity.

There are two types:

Sclereids are short and irregular in shape and have thick lignified secondary walls.

Fibers are long and slender and arranged in threads.

Slide 27

Fig. 35-10c

5 µm

25 µm

Sclereid cells in pear (LM)

Fiber cells (cross section from ash tree) (LM)

Cell wall

Slide 28

Differentiated Plant Cells in the Xylem - Dead at Maturity

Perforation