Specialized Tissues in Plants

Seed Plant Structures

§    Seed plant cells are organized into three different tissues and organs:

            1. Roots

            2. Stems

            3. Leaves

§    Linked together by systems that run the length of the plant performing functions such as:

v    Transport

v    Protection

v    Coordinating plant activities

Roots

1. absorbs water and dissolved nutrients

2. anchor plants in the ground, hold soil in place, and prevent erosion

3. store food (starch)

Stems

1. support system for the plant body

2. transport system that carries nutrients

3. defense system that protects the plant against predators and disease

Leaves

1. main photosynthetic system

2. contain subsystems to protect against water loss

Plant Tissue Systems

§    Plants consist of three main tissue systems:

            1. dermal tissue - like the "skin" of a plant or the outermost layer of cells

            2. vascular tissue - like the plants "bloodstream", transporting water and

                      and nutrients throughout the plant

            3. ground tissue - everything else!

Dermal Tissue

§    Dermal tissue (outer covering of a plant) consists of a single layer of epidermal cells, and covered with the cuticle, a thick waxy coating that protects against water loss.

§    Examples:

            1. Trichomes are tiny projections which protect the leaf and give it a

                    fuzzy appearance.

            2. Root hair cells provide a large amount of surface area and aid in water

                    absorption.

            3. Guard cells are on the underside of leaves and regulate water loss

                    and gas exchange.

Vascular Tissue

§    Vascular tissue forms a transport system that moves water and nutrients throughout the plant.

§    Principle subsystems are:

            1. Xylem - a water-conducting tissue

w   Consists of tracheids (long, narrow cells with walls that are impermeable to water) and vessel elements (wider than tracheids and stack on top of one another for continuous water flow)

            2. Phloem - a food-conducting tissue

w   Consists of sieve tube elements, (arranged end to end and form a pipeline which sugars and other foods flow through) and companion cells (surround sieve tube elements and support phloem cells)

§    They are both a network of hollow connected cells that carry fluids throughout the plant.