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Plant Structure, Growth, and Development
Chapter 35
PLANTS
developmental plasticity = ability of plant to alter form to respond to environment
Biological heirarchy
• Cell – basic unit of life
• Tissue – group of cells perform a common function
• Organ – multiple tissue types with a common function
• Organ system – multiple organs with common function
• Organism – all of above
Example
Parenchyma cells
Plant epidermis
Leaf
Shoot system
Plant
PLANTS Moss, ferns, gymnosperms, angiosperms
ORGAN SYSTEMS
1. Root System Root (organ)
Anchors plant
Absorbs minerals and water
Stores food
Root hairs
Absorption of water
and minerals
Large surface area
Renewed continually
Extension of root
epidermis
Radish seedling
Extension of epidermis
A. Taproot system
Embryonic root Taproot = main
vertical root, deep
Stores sugar, starch
So, harvest carrots before they flower
Lateral roots
deep
Radish, mustard, carrot,
B. Fibrous root system (embryonic root dies)
Begins with Adventitious roots
Roots arise from stems or leaves
Shallow mat
Maize: Prop roots are adventitious
From stem on bottom of bulb canary island date palm
Monocots and seedless vascular plants
ferns
grains, grass, lilies, onions
scallion
grass
fern
2. Shoot system
Stem (organ)
Nodes = points at which leaves are attached
– Internodes= stem segments between nodes
– Axillary bud can form a lateral shoot, or branch
– Apical bud near shoot tip for elongation
• Apical bud is dominant
– Pinch off apical bud plant grows laterally
Stem adaptations: Rhizome =modified stem (shoot below surface)
iris ginger bamboo
Storage leaves
Stem
Onion bulb is an
underground shoot
Stolons of strawberry plant
Stolon= horizontal
shoot or runner
Tubers = enlarged rhizome ends
Eye is cluster of axillary buds (can plant)
Leaves (organs) • Photosynthesis
• Blade
• Petiole
– stalk joins leaf to node of stem
• cc
Simple =single
blade
Compound - blade
has multiple leaflets
Doubly compound =
each leaftlet divided
into smaller leaflets
LEAF MORPHOLOGY (shape)
• Leaf veins = vascular tissue of leaves
• parallel veins
– ex. lily, orchid, grass (monocots)
• branching veins
– Ex. apple, maple, dandelion (eudicots)
Grape (Vitis) daylily mint
Plant tissues
1. Dermal tissue system
• Protection against:
– Water loss
– Disease
– Damage
A. Epidermis (non-woody plants)
– Waxy cuticle on leaves, stems
Specialized epidermis
Trichomes
– Hair-like
– Reduce water loss
– Reflect excess sunlight
– May secrete sticky or toxic fluids
– May sense prey (carnivorous plants)
B. Periderm (woody plants) from epidermis
– On older stems and roots (cork, bark)
Very hairy pod
(10 trichomes/
mm2)
Slightly hairy pod
(2 trichomes/
mm2)
Bald pod
(no trichomes)
Very hairy pod:
10% damage
Slightly hairy pod:
25% damage
Bald pod:
40% damage
EXPERIMENT
RESULTS
Does soybean
trichome density
relate to beetle
damage?
Read experiment
Chapter 35
Cerotoma trifurcata, the bean leaf beetle
Dermal tissue
Ground tissue Vascular
tissue
Fig 35.8
2. vascular tissue system long-distance transport from roots to shoots
• Xylem tissue • Transports water, minerals from roots shoots
• One way transport
• Older xylem = wood
• Phloem tissue • transports sugars from leaves to where needed
(leaves, fruits)
• 2 way transport
Xylem vessels – cells not alive at maturity
Phloem – cells alive at maturity
3. ground tissue system – Storage
– Photosynthesis
– Support
• pith tissue internal to vascular tissue
• cortex tissue external
A transverse section of corn (Zea mays) internode showing ground
tissue
Plant growth
• Mature plant contains
• Embryonic cells
• Developing organs
• Mature organs
Life cycles
• Annuals complete life cycle in <year
• Germinate grow flower seed
• Biennials require two growing seasons
foxglove thistle sweet william
• Perennials live for many years
PLANT GROWTH
• Determinant growth
– Some organs grow to certain size
• Leaves
• Flowers
Indeterminate growth
• Plant grows throughout life
• Meristems = embryonic tissue
• Apical meristems for primary growth • Tips of roots, shoots, leaves
• New cells either remain as meristematic or differentiate
• Apical meristem in stem with leaf primordium
• Apical meristem in root
Primary Growth of Roots
• root cap covers root tip
– protects apical meristem as root pushes through soil
Primary Growth of Shoots
• Leaves from leaf primordia
• Note: Axillary buds
• Lateral meristems
• Secondary growth
• Roots and stems
• Increases thickness
• Woody plants
Organization of stems • Vascular bundles of tissue
Monocot bundles throughout stem
Eudicot bundles in outer ring
Same tissues different arrangement
Monocot ex. corn, grass
Eudicot example:
African violet
Organization of Leaves Stomata In epidermis
guard cells regulate stomata opening and closing
mesophyll
ground tissue of leaf
Between upper and lower epidermis
Scanning electron microscope image of leaf from a Black Walnut tree. Image shows a cross-
section of a cut leaf, its upper epidermal layer, mesophyll layer with palisade cells and vascular
bundles, and lower epidermal layer. Dartmouth College
RMS
• Monocot leaf
• Eudicot leaf
Same tissues, different arrangements