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Biology
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2. 23–1 Specialized Tissues in Plants
Photo Credit: Getty Images
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Seed Plant Structure
Seed Plant Structure
What are the three principal organs and tissues of seed plants?
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Seed Plant Structure
The three principal organs of seed plants are roots, stems, and leaves.
These organs perform functions such as the transport of nutrients, protection, and coordination of plant activities.
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Seed Plant Structure
Roots:
absorb water and dissolved nutrients.
anchor plants in the ground.
protect the plant from harmful soil bacteria and fungi.
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Seed Plant Structure
Stems provide:
a support system for the plant body.
a transport system that carries nutrients.
a defense system that protects the plant against predators and disease.
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Seed Plant Structure
Leaves:
are a plant’s main photosynthetic systems.
increase the amount of sunlight plants absorb.
Adjustable pores conserve water and let oxygen and carbon dioxide enter and exit the leaf.
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Plant Tissue Systems
Plant Tissue Systems
What are the three main tissue systems of plants?
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Plant Tissue Systems
Plants consist of three main tissue systems:
dermal tissue
vascular tissue
ground tissue
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Plant Tissue Systems
Leaf
Stem
Vascular plants consist of roots, stems, and leaves. Each of these organs contains dermal tissue, vascular tissue, and ground tissue.
Root
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Dermal Tissue
Dermal Tissue
The outer covering of a plant consists of epidermal cells.
Epidermal cells make up dermal tissue.
The outer surfaces of epidermal cells are covered with a thick waxy layer, known as the cuticle. The cuticle protects the plant against water loss and injury.
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Dermal Tissue
Some epidermal cells have projections called trichomes, that help protect the leaf and also give it a fuzzy appearance.
In roots, dermal tissue includes root hair cells that provide a large amount of surface area and aid in water absorption.
On the underside of leaves, dermal tissue contains guard cells, which regulate water loss and gas exchange.
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Vascular Tissue
Vascular Tissue
Vascular tissue forms a transport system that moves water and nutrients throughout the plant.
Vascular tissue is made up of xylem, a water-conducting tissue, and phloem, a food-conducting tissue.
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Vascular Tissue
What specialized cells make up vascular tissue?
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Vascular Tissue
Vascular Tissue
Vascular tissue contains several types of specialized cells.
Xylem consists of tracheids and vessel elements.
Phloem consists of sieve tube elements and companion cells.
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Vascular Tissue
Cross Section of a Stem
Tracheid
Companion cell
Vascular tissue is made up of xylem and phloem. Xylem tissue conducts water from the roots to the rest of the plant. Phloem tissue conducts a variety of materials, mostly carbohydrates, throughout a plant. Photo Credit: Ray F. Evert, University of Wisconsin
Vessel element
Sieve tube element
Xylem
Phloem
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Vascular Tissue
Xylem
All seed plants have tracheids.
Tracheids are long, narrow cells that are impermeable to water. They are pierced by openings that connect neighboring cells to one another.
Tracheid
Vessel element
Vascular tissue is made up of xylem and phloem. Xylem tissue conducts water from the roots to the rest of the plant.
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Vascular Tissue
Angiosperms also have vessel elements.
Vessel elements form a continuous tube through which water can move.
Tracheid
Vessel element
Vascular tissue is made up of xylem and phloem. Xylem tissue conducts water from the roots to the rest of the plant.
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Vascular Tissue
Phloem
Phloem contains sieve tube elements and companion cells.
Sieve tube elements are phloem cells joined end-to-end to form sieve tubes.
Companion cell
Sieve tube element
Vascular tissue is made up of xylem and phloem. Phloem tissue conducts a variety of materials, mostly carbohydrates, throughout a plant.
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Vascular Tissue
The end walls of sieve tube elements have many small holes.
Sugars and other foods can move through these holes from one adjacent cell to another.
Companion cell
Sieve tube element
Vascular tissue is made up of xylem and phloem. Phloem tissue conducts a variety of materials, mostly carbohydrates, throughout a plant.
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Vascular Tissue
Companion cells are phloem cells that surround sieve tube elements.
Companion cells support the phloem cells and aid in the movement of substances in and out of the phloem.
Companion cell
Sieve tube element
Vascular tissue is made up of xylem and phloem. Phloem tissue conducts a variety of materials, mostly carbohydrates, throughout a plant.
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Ground Tissue
Ground Tissue
Cells that lie between dermal and vascular tissues make up the ground tissues.
The three kinds of ground tissue are:
parenchyma
collenchyma
sclerenchyma
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Ground Tissue
Parenchyma cells have thin walls and large central vacuoles surrounded by a thin layer of cytoplasm.
Collenchyma cells have strong, flexible cell walls that help support larger plants.
Sclerenchyma cells have extremely thick, rigid cell walls that make ground tissue tough and strong.
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24. Plant Growth and Meristematic Tissue
In most plants, new cells are produced at the tips of the roots and stems.
These cells are produced in meristems.
A meristem is a cluster of tissue that is responsible for continuing growth throughout a plant's lifetime.
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25. Plant Growth and Meristematic Tissue
The new cells produced in meristematic tissue are undifferentiated.
As the cells develop into mature cells, they differentiate.
Differentiation is the process in which cells become specialized in structure.
As the cells differentiate, they produce dermal, ground, and vascular tissue.
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26. Plant Growth and Meristematic Tissue
Near the tip of each growing stem and root is an apical meristem.
An apical meristem is a group of undifferentiated cells that divide to produce increased length of stems and roots.
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27. Plant Growth and Meristematic Tissue
How does meristematic tissue differ from other plant tissue?
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28. Plant Growth and Meristematic Tissue
Meristematic tissue is the only plant tissue that produces new cells by mitosis.
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23–1
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23–1
The principle organs of seed plants are
reproductive organs and photosynthetic organs.
stems, leaves, and flowers.
roots, vessels, and cones.
leaves, stems, and roots.
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23–1
Phloem cells that surround sieve tube elements are called
epidermal cells.
cuticle cells.
companion cells.
vessel elements.
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23–1
Which type of ground tissue has thin cell walls and large central vacuoles?
parenchyma
collenchyma
sclerenchyma
tracheids
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23–1
Cells that can differentiate into many plant tissues are found in
the vascular cylinder.
dermal tissue.
meristematic tissue.
ground tissue.
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23–1
When cells in the apical meristem first develop, they are
highly specialized and divide often.
unspecialized and divide rarely.
highly specialized and divide rarely.
unspecialized and divide often.
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