Download - Roots , Stems, and Leaves
Roots, Stems, and Leaves
Specialized Tissues In Plants
A.Seed Plant Structure1. Roots2. Stems3. Leaves
B.Plant Tissue SystemsC.Dermal TissueD.Vascular Tissue
1. Xylem2. Phloem
E. Ground TissueF. Plant Growth and Meristematic Tissue
Seed Plant Structure• The cells of seed plants are organized into
tissues and organs.• The three main plant organs are roots,
stems, and leaves.– Roots absorb water and dissolve
nutrients and anchor plants in the ground.
– Stems support the plant body and transport materials throughout the plant.
– Leaves are the main organs of photosynthesis. They also function in gas exchange.
Dermal tissue
Vascular tissue
Ground tissue
Stem
Root
Leaf
Root, Stem, and Leaf Tissues
Plant Tissue Systems• Within the roots, stems, and leaves are specialized tissue
systems. The three main tissue systems:– Dermal tissue is like the skin of a plant. It protects the
plant and prevents water loss.– Vascular tissue consists of xylem (move water
throughout the plant) and phloem (moves sugars and other materials throughout the plant).
– Ground tissue is made up of all of the cells that lie between dermal and vascular tissues. (made up of 3 kinds of cells)• Parenchyma cells: function in photosynthesis and
storage• Collenchyma cells: help support larger plants• Sclerenchyma cells: make ground tissue tough and
strong
Plant Tissue Systems Cont.• A fourth kind of tissue, meristematic tissue, is responsible for
plant growth.– Meristematic tissue is the only plant tissue that produces
new cells by mitosis.– The tips of stems and roots are made of meristematic
tissue.
Concept Map
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Plant Tissues
Dermaltissue
Meristematictissue
Vasculartissue
Groundtissue
Epidermalcells Xylem Phloem Parenchyma
cellsCollenchyma
cellsSchlerenchyma
cells
Tracheids Vesselelements
Sieve tubeelements
Companioncells
Roots
• The two main types of roots are taproots and fibrous roots.• Taproots: the primary root grows long and thick, while the
secondary roots stay small.• Fibrous roots: secondary roots that grow and branch out • Roots have two main functions– To anchor a plant in the ground– To absorb water and dissolved nutrients form the soil
Taproots and Fibrous Roots
• Taproots (Carrots) Fibrous Roots (Grasses)
Epidermis
Ground tissue(cortex)
VascularCylinder
Cross Section of Plant Root(magnification: 40x)
Ground tissue (cortex)
Epidermis
Endodermis
Vascular cylinder
Root hairs
Phloem
Xylem
Apical meristem
Root cap
Zone of maturation
Zone of elongation
Endodermis
The Structure of a Root
Stems• Stems have three important functions– To produce leaves, branches, and flowers– To hold leaves up to the sunlight– To carry water and nutrients between the roots and leaves
Comparing Primary and Secondary Growth of Stems
Characteristics
Where It Occurs
Effect on Plant
How It IsProduced
Primary Growth Secondary Growth
Plant stems grow in two ways
At ends of plants
Increases plant length
By cell division in the apical meristem
In stem
Increases stem width
By cell division in meristems other thanthe apical meristem
Leaves
• The structure of a leaf is optimized for absorbing light and carrying out photosynthesis.
• To collect sunlight, most leaves have thin, flattened sections called blades.
• Plants can lose water out of their leaves as they exchange gases with the air (transpiration).– To prevent major water loss plants allow air in and out of
their waterproof covering only through small openings called stomata.
– Plants keep their stomata open just enough to allow photosynthesis to take place but not so much that they lose an excessive amount of water.
Evaporation of water molecules out of leaves.
Pull of water molecules upward from the roots.
A B
Transpiration
Blades On Leaves
Veins
XylemPhloem
Vein
Cuticle
Epidermis
Palisademesophyll
Epidermis
Stoma
Guardcells
Spongymesophyll
The Internal Structure of a Leaf
Transport in Plants
• Forces of Attraction• Molecules of a similar substance are attracted to one
another by a force called cohesion.
• Molecules of different substances are attracted to one another by a force called adhesion.
Movementof water
Movementof sugar
Sugarmolecules
Source cell
Sink cell
Phloem Xylem
Transport In Plants