Plant Anatomy and
Nutrient Transport
Chapter 42
Tracheophytes
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Tracheophytes – plants w/ vascular tissue
Tracheophytes show indeterminate growth
Divided into 2 groups:
Angiosperms (flowering plants)
Gymnosperms (non-flowering plants)
Shoot – one or more stems w/ leaves
Meristematic tissue – growing tissue at stem or root tip
Primary growth – growth in length
Secondary growth – growth in width
Apical meristems are found in all green plants
Lateral meristems – found w/in stems, causes increase
in width
Tracheophytes Growth Patterns
• Annuals – grow for one year, reproduce &
die
• Biennials – grow for 2 years, reproduce 2nd
year & die
• Perennials – grow for many years,
reproduce for many years & die
• Angiosperms are divided into two groups
(monocots and dicots) based on the
structure of their flowers, leaves, vascular
tissue, roots, and seeds
Monocots & Dicots
• Monocots have one cotyledon (seed leaf)
– e.g. grasses, lilies, palms, orchids
• Dicots have two cotyledons (seed leaves)
– e.g. deciduous trees (drop leaves in winter),
bushes, many garden flowers
Types of stems
• Herbaceous stems – small, soft nonwoody stems. ex. Tomato
• Usually found in annuals & biennials
• Woody stems – vascular plants w/ large
woody bodies ex. Trees, shrubs
Stem Function
• Support plant
• Translocation of materials between roots &
leaves
• Storage of food & water
• Some photosynthesis in herbaceous
stems
• Some help produce new plants
• Hold leaves in position, max exposure to
sunlight
Stem Structures
• Cuticle – waxy, waterproof coating
• Epidermis – cells under cuticle, aid in
protecting stem
• Vascular bundles – composed of
collenchyma cells
• Pith – storage & support tissue near center
• Monocots no pith, dicots do
Plant Tissues
• Collenchyma – column shaped cells w/
thick walls. Support soft stems as well as
xylem & phloem. Living
• Parenchyma – cells w/ round x-section,
thin walls. Living
• Pith in herbaceous dicots contains
parenchyma cells w/ chloroplasts
• Sclerenchyma – non-living cells, w/ lignin
Arrangements of Vascular Bundles
• Herbaceous monocots – bundles arranged
randomly ex. Corn
• Herbaceous dicots – bundles arranged in
a circle ex. Bean
Woody Stems
• Tissues arranged in rings
• Vascular cambium – forms new plant
tissue. Phloem toward the bark, xylem
toward the middle
• Primary xylem & phloem – ring of bundles
@ outer edge of stem for transport
• Secondary xylem – develops into wood of
the stem
Woody Stems
• Bark & epidermis protects against disease &
mechanical injury
• Cork cambium – beneath epidermis forms cork
or outer bark
• Pith – heartwood at center, stores water &
minerals
• Annual rings – separates summer & spring wood
• Lenticels – cracks in outer bark, allow gas
exchange
• Twig – finer branches of tree, bear flowers, fruits
Twig Structure
• Buds – groups of bud scales (modified
leaves)
• Leaf scars – regions where leaves have
fallen off
• Terminal buds – become leaves at tip of
stem (from apical meristem)
• Lateral buds – become leaves at side of
stem
Roots
• 3 basic types of roots:
• 1. Taproot – thick, fleshy root. Stores
water & starch. Ex. Carrot
• 2. Fibrous roots – threadlike roots ex.
Grass
• 3. Adventitious – help prop up the plant ex.
corn
Root Functions
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1. Anchor plant into soil
2. Store food material
3. Transport materials
4. Absorb water & minerals
• 5. Absorb O2 in aerated soils
Root Structures
• Root cap – layer of dead cells at root tip,
protection
• Endodermis – contains pericycle. Controls
movement of materials
• Pericycle – meristematic cells, produces new
cells when needed
• Meristematic region – cells actively divide
• Elongation region – area where cells become
longer
• Differentiation region – area where cells
differentiate & become mature
• Root hairs – root epidermis projections. Aid in
Root Relationships
• Symbiotic relationships help plants acquire
nutrients
• Mycorrhizae (root-fungus symbiosis)
– Fungus helps plant extract and absorb minerals
– Plant supplies fungus with sugars, amino acids, and
vitamins
• Legumes (peas, clover, soybeans) house
nitrogen-fixing bacteria in nodules (swellings)
on their roots
– Plant supplies bacteria with sugars
– Bacteria supplies plant with usable nitrogen
Transport
• Capillary action – water creeps up xylem
(small dia.) due to cohesion & adhesion
• Only will pull water up several cm
• Transpirational pull – loss of water through
leaves pulls water up through the plant
• Major way of upward transport
• Root pressure – pressure of water
entering roots forces water up the plant
Xylem
• Conducts water and minerals from roots to
shoots
• Tracheids – long, thin, thick walled, dead cells
• Vessels – short, wide, thick walled, dead cells
• Fibers – long, thick walled, dead cells,
strengthen xylem
• Sclereids – variable shaped, thick walled, dead
cells, strengthen xylem
• Parenchyma – un-specialized living cells. Store
starch, help w/ lateral conduction
Phloem
• Conduct sugars, hormones, aa & some
minerals
• Sieve cells – large, column-like living cells.
Cytoplasm is continuous w/ another sieve
cell
• Cytoplasmic bridges allow direct pathways
from roots to leaves
• Companion cells – Small, column-shaped,
living cells. Care for sieve cells
• Phloem fibers – support phloem structure
Mass Flow
• Mass Flow – aka pressure flow or solution
flow. Idea that osmotic pressure w/in
sieve cells force mass of solutes to flow
along a phloem gradient for mass.
• Differences in water pressure drive sap
through phloem sieve tubes
• Sugars are transported from sources to
sinks