Download 35 Plant

Plant
Structure, Growth
and
Development
Types of Plants
Nonvascular
Vascular
•earliest plants, related to algae
•no special vascular tissues devoted to
transport
•grow close to ground, near water
•use spores rather than seeds to
reproduce
•have true leaves, stems, roots
•vascular tissues: create “tubes” through
plants
•mosses
•liverworts
•hornworts
Plant Organization
Plants have three levels of organization:
Organs
• roots, stems, leaves
Tissues
• dermal, vascular, ground
Cell Types
• Xylem, phloem, parenchyma
Plant Structures
Root System
•below ground
•multifunction
Shoot System
•stem, branches, leaves,
flowers and fruit
•vegetative shoots- stems and
leaves
•floral shoots- bear flowers
•above ground
Roots
• Multicellular organs
• Anchors the plant
• Absorbs minerals and water
• Stores organic nutrients (sugars/starches)
• Root hairs: tiny extensions of epidermal cells
• Increase surface area for absorption
• Mycorrhizae: fungus + root
symbiotic relationship
Root Anatomy
Root types
Taproots
•One thick, vertical root
•Many lateral (branch) roots
•Firmly anchors
•Stores food
Fibrous
•Mat of thin roots spread just
below surface
•Shallow
•Increased surface area
Modified Roots
Stems
Function: display leaves
Consists of:
• nodes- where the leaves are attached
• internodes- stem segments between nodes
- can be herbaceous (non-woody) or woody
- used for support and conduction
- two kinds of buds
1. axillary buds- found in the angle
between the leaf and the stem
2. terminal buds- found at the end of
the stem
(where most growth occurs)
Modified Stems
Runner or stolin
Aspen, strawberries, grass
Grow on surface
For asexual reproduction
Rhizome
Iris, ginger, potato, onion
Grow underground
Store food & DNA for new plant
Tuber: end of rhizome
Bulb – underground shoot
Onion
storage leaves
Leaves
Function: photosynthetic organ
Blades: flattened
Petiole: stalk- joins leaf to node
of a stem
•Most monocots have parallel
veins
•Most eudicots have
branching veins
Leaf Anatomy
Layers
Epidermis : two exterior surfaces (upper and lower)
•cuticle - waxy coat produced by epidermis
•protects against water loss and fungal
or bacterial attack
•stomata- small openings on the underside of the
leaf
- transpiration (gas diffusion)
•guard cells swell or relax to close or open stomata,
limit gas and water exchange
Mesophyll: layer in between epidermis
- rich in chloroplasts
•
•
palisade layer
- chloroplasts in columns just below the
epidermal cells
spongy layer
- cells are less ordered , large intercellular
spaces
- facilitate the exchange of CO2 and O2
Modified Leaves
Plant Tissues
Dermal (epidermis)
- protects exterior of plant’s body
- forms root hairs
Vascular
- phloem
- xylem
Ground (Parenchyma)
- non dermal or vascular
- pith
- cortex
Plant Tissues- Dermal
• Single layer
• closely packed cells- cover entire plant
• Protect against water loss & invasion by pathogens
• Cuticle: waxy layer
Plant Tissues- Vascular
•Continuous throughout plant
•Transports materials between
roots & shoots
•xylem – water,minerals
roots shoots
• phloem- organic
nutrients from leaves
to where needed
Plant Tissues- Ground Tissue (Parenchyma)
•Anything that isn’t dermal or
vascular
•Most common- make up the
bulk of soft parts of plants
•Function: storage,
photosynthesis, support
•Pith: inside vascular tissue
•Cortex: outside vascular tissue
Plant Growth
Growth Patterns
• Indeterminate growth:
plant can grow throughout its life
• Determinate growth:
Plant ceases to grow at a certain size
Plant Types:
• Annuals complete their life cycle in a year or less
• Perennials live for many years
Growth Types
Primary and Secondary Growth
Primary Growth (length)
vertical growth of apical meristem in roots and shoots
Roots
Shoots
dome of dividing cells at tip of terminal
bud; divide and elongate
Secondary Growth (diameter)
Occurs in lateral meristem in roots and
shoots
• Vascular cambium: produces
secondary xylem (wood)
• Cork cambium: produces tough
covering that replaces epidermis
Bark = all tissues outside
vascular cambium