Download Plant Structure and Function

Plant Structure and Function
Plant Cells and Tissues
Plant Cells
• Three basic types
– Parenchyma
– Collenchyma
– Sclerenchyma
Parenchyma
• Loosely packed w/large central vacuole
• Cubed – shaped or elongated
• Involved in
– Photosynthesis
– Water storage
– Nutrition or healing
• Bulk of nonwoody plants
• Fleshy parts of fruit
Collenchyma
• Thicker cell walls
• Irregular shape
• Support for plant
Sclerenchyma
• Thick, even, rigid cell walls
• Support and strengthen plant
• Dead at maturity
– Hardness of shells around nuts
Plant Tissue Systems
• Dermal
• Ground
• Vascular
Dermal Tissue
• Forms outside covering
– Epidermis
– Parenchyma cells
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•
•
•
Cuticle
Roots develop hair – like extensions
Stomata
Woody stems/roots replaced by dead cork
cells (parenchyma)
Ground Tissue
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•
•
•
Surrounded by dermal tissue
All three types of plant cells
Make up majority of nonwoody plants
Main function
– Storage
– Metabolism
– Support
Vascular Tissue
• Surrounded by ground tissue
• Made up of
– Xylem
• Conducts water, mineral nutrients from roots upward
• Provides structural support
– Phloem
• Conducts organic compounds, some mineral nutrients
• Alive a maturity
• Adapted to different environmental conditions
– Xylem support and strength
• May be absent in aquatic species
Plant Growth
• Flowering plants (Angiosperms)
– Dicotyledons
– Monocotyledons
• Number of cotyledons or seed leaves in a plant embryo
• Gymnosperms
– Have two or more cotyledons
Monocot and Dicots
Plant type
Embryo
Leaves
Stems
Flower Parts Examples
Monocots
One
cotyledon
Parallel
Venation
Scattered
vascular
bundles
Usually
occur in
threes
Lilies, irises,
onions,
grasses
Dicots
Two
cotyledons
Net
venation
Radially
arranged
vascular
bundles
Usually
occur in
fours or
fives
Beans, oaks,
lettuces,
maple,
roses,
cactuses,
carnations
Plant Growth
• Originates in meristems
– Continuous cell division
• Apical meristem (primary growth, length)
• Lateral meristem (secondary growth, diameter)
– Some monocots grow in length
• Intercalary meristems
• Located above the base of the leaves or stems (grasses)
• Allows plants to regrow quickly after being grazed on
Lateral Meristems
• Gymnosperms and most dicots
• Allow stems and roots to increase in diameter
• Located outside of stem
Lateral Meristem
• Two types
– Vascular cambium
• Located b/w xylem and phloem
– Cork cambium
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•
•
•
Located outside phloem
Produces cork
Replaces epidermis
Provides protection and prevents water loss
Plants have three kinds of organs
• Roots
• Stems
• Leaves
Roots
• Anchor the plant in the soil
• Absorb and transport water and mineral
nutrients
• Storage for water and organic compounds
Types of Roots
• Taproot
– Primary root
– Rarely more than one – two meters
• Fibrous root system
– Numerous small roots
• Adventitious roots
– Specialized roots grow from other places
– Leaves and stems
– corn and epiphytic orchid (aerial roots)
Root Structures
• Root cap
– Covers apical meristem
– Produces oil
• Root hairs
– Extensions of epidermal cells
– Increase surface area
• Dependent on stems and leaves for energy
• Store starch
Primary Growth in Roots
• Increase length through cell division of the
apical meristem
• Dermal tissue matures for form the epidermis
• Ground tissue matures into
– Cortex
– Endodermis
• Large portion of the root is made up of
parenchyma cells
• Endodermis
– Inner most boundary of cortex
– Semipermeable membrane (waxy layer)
– Controls the flow of dissolved substances
• Vascular tissue
– Makes up innermost core of root
– Dicots and gymnosperms
• Xylem makes up central core
• Usually forming an X
• Pockets of phloem b/w lobes
– Monocots
• Xylem occurs in patches that circle the pith
(parenchyma)
• Phloem occurs b/w the xylem patches
• Outermost layer of vascular tissues
– Pericycle
– Form lateral roots