Plant Structure and Function
Chapter 21
PLANT CELLS AND TISSUES 21.1
Key Concept
• Plants have specialized cells and tissue systems.
Plant Cells
• 3 basic types
• Make up plant tissues
Plant Tissues
• Make up plant organs – meristematic
– ground
– dermal
– vascular
Meristematic Tissue
• Made of undifferentiated cells
• Found in areas where growth is occuring – root tip
– shoot tip
Ground Tissue
• Found inside a plant – provides support
– stores materials in roots and stems
Dermal Tissue
• Covers the outside of the plant – protects the plant
– secretes cuticle of leaves
– forms outer bark of trees
Vascular Tissue
• Transports water, minerals and organic compounds – two networks of hollow
tubes – xylem transports water
and minerals – phloem transports
photosynthetic products
THE VASCULAR SYSTEM 21.2
Key Concept
• The vascular system allows for the transport of water, minerals, and sugars.
Xylem
• Tissue that transport water and dissolved minerals through plants – cells are dead at
maturity
Water Movement
• The cohesion-tension theory explains water movement – passive transport of water
Water Movement
• Water travels from the roots upward – absorption occurs at roots
– cohesion and adhesion in xylem
– transpiration at leaves
Transpiration
• The loss of water vapor through leaves – water vapor exits leaf
stomata
– helps pull water to the top branches
Phloem
• Tissue that carries sugars from photosynthesis throughout the plant – cells are alive
ROOTS AND STEMS 21.3
Key Concept
• Roots and stems form the support system of vascular plants
Roots
• Anchor plants
• Absorb mineral nutrients from soil – root hairs
• increase surface area for absorption
– root cap • protects growing
root
Types of Roots
• Fibrous Roots – have fine branches
Fibrous root Taproot
• Taproots – have one main root
Stems
• Support leaves and flowers
• House most of the vascular system
• Store water
Baobab trees Cactus
Stems
• Grow underground for storage
• Form new plants
• Some perform photosynthesis
• Some make up bark
Ginger rhizomes Potato tubers
LEAVES 21.4
Key Concept
• Leaves absorb light and carry out photosynthesis
Leaves
• Most leaves share similar structures – blade is broad and
flat • collect sunlight for
photosynthesis
• connects to the stem by a petiole
blade
petiole
Guard Cells
• Surround each stomata – stomata open and close when guard cells
change shape • when stomata are open, water evaporates and gas
exchanges • stomata close at night and when plant loses too much
water
Leaf Shape
• Leaves may be simple, compound, or double compound
Simple leaf Compound leaf Double compound leaf
Leaf Veins
• Leaf veins may be parallel or pinnate
Pinnate veins Parallel veins
Leaf Margins
• Leaf margins may be toothed, entire, or lobed
Toothed margin Entire margin Lobed margin
Leaf Adaptations
• For extreme temperatures – pine needles
Leaf Adaptations
• For water loss – cactus spines
Leaf Adaptations
• For aquatic environments – water lily
Leaf Adaptations
• For getting food – Venus flytrap
– Pitcher plant