Download secondary growth

Angiosperms
• Flowering plants
• Most diverse group of plants
(~275,000 species)
• Divided into two taxonomic groups
– Monocots
– Dicots
Shoot System
• Vegetative – stem and leaves
– Photosynthesis
• Floral – end in flowers
– Reproductive structures
Shoot
Morphology
• Nodes – leaves
attach to stems
• Internode – stem
between nodes
• Terminal bud –
shoot tip
• Axillary bud –
base of node
Bulbs and Rhizomes
Runners and Tubers
Tendrils and Cladophylls
Leaf Morphology
• Monocots
– Parallel veins
• Dicots
– Multi-branched network
– Palmate or pinnate veins
Blade
Petiole
Roots System
• Anchor plant
• Absorb and conduct water and nutrients
• Store food
Types of Root Systems
• Fibrous
– Most monocots
– Small, close to surface
• Taproot
– Most dicots
– Long central root
Increased Surface Area
• Root hairs
– Extensions off of surface root cells
• Mycorrhizae
– Symbiotic association between roots and fungi
Specialized Roots
• Store food
– Thickened taproot
– Example – carrot
• Adventitious roots
– Grow from stems
– Example – prop roots of
corn
Basic Plant Cell Anatomy
Parenchyma and Collenchyma Cells
Collenchyma Cells
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Thick primary cell walls
Most lack secondary cell walls
Stacked cylinders
Support young plants
Parenchyma Cells
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Thin and flexible primary cell wall
Most lack secondary cell walls
Large central vacuole
Photosynthesis and storage of food
Sclerenchyma Cells
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Rigid secondary cells wall with lignin
Protoplast die at maturity
Fibers – long thin bundles
Sclerids – short irregular shapes
Vascular Cells
• Xylem
– Water and minerals
– Direction – roots to
shoots
• Phloem
– Water, sugar, hormones
– Both directions
Xylem Structure
Tracheids
– Bundles of small diameter tubes
– Pits in end wall allows water and minerals to flow
from cells to cell
Xylem Structure
Vessel elements
– Large diameter
– End wall either absent or perforated
• Pits allow water and minerals to flow
between vessel element and tracheid
• Vessel element die after development and
add support to the plant
Phloem Structure
• Sieve-tube element
– End wall is perforated forming sieve plate
– Lose most of their internal components – only has
plasma membrane, few mitochondria and some
endoplasmic reticulum
• Companion cells
– Support and nourish adjacent sieve-tube elements
• Vascular system is a
continuous network
of tubes
Leaf Anatomy
Leaf Summary
• Stoma
– Controls transpiration (water loss through leaves)
• Spongy/palisade layer
– Exchange of gases
– Photosynthesis
• Epidermis
– Transparent
– Wax coating to prevent water loss
• Vascular bundle
– Brings water and mineral to leaf through xylem
– Sends sugars to roots through phloem
Stoma
Plant Tissues
• Dermal
– Outside covering
– Epidermis
• Stems and leaves – waterproof wax coating
• Roots – root hairs – absorb water
– Periderm
• Bark
• Ground
– Photosynthesis, support, storage
• Vascular
– Transport
• Xylem – water and minerals
• Phloem – water, sugar, amino acids, hormones
Plant Growth
• Apical meristem
– End of roots and shoots
– Increases length – primary growth
• Lateral meristem (cambia)
– Cylinder of cells along roots, branches and
stems
– Increases width – secondary growth
Root Growth
Terminal Bud Growth
Monocot Stem
Dicot Stem
Dicot Secondary Growth
Annual Growth Rings