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