Transcript Plant Structure and transport

Plant Structure and Growth
Chapter 35
Monocots vs. dicots
Page 595
Monocot or Dicot?
Monocot or Dicot?
Monocot or Dicot?
Monocot or Dicot?
Annuals vs. perennials
 Annuals live for a year
 Examples??
 Perennials live for several years
 Examples??
PLANT BODY PARTS
Roots
 Fibrous Root systems
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Monocots
Anchor plants
Prevent erosion
Increases surface area for absorption of
water and nutrients
Taproot Systems
 Dicots
 Anchor plants
 Stores food
 Carrots, turnips, sugar beets
 Can go far below ground
 Desert plants
Root Hairs
 Epidermal
extensions
 Increase surface
area
Symbiosis with fungi
 Most plants have mutualistic partnership
with fungi forming a root/fungus structure
called mycorrhizae
 Fungi absorb water and select minerals
for host plant (HUGE surface area)
 Host plant nourishes fungus
Stems
 Support
 transport
Leaves
 Typical leaves
 Flattened blades
 Petioles – join leaf to the stem node
 Specialized leaves to reduce water loss?
 Specialized leaves to store water?
CELL TYPES
Parenchyma
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Most abundant type
“typical” plant cell
Thin cell walls
Most photosynthetic
and storage tissue,
phloem, fruit tissue
 Starch grains from
potato tuber,
stained with I2KI.
 Cross section of Phormium (New Zeland
flax) leaf. Note large areas of supporting
fibers and thin-walled parenchyma cells
that function in water storage.
Collenchyma
 Thicker cell walls
 Provides support for
young shoot, petioles
Sclerenchyma
 Supports
 Thickest cell walls
 May be dead at
maturity (xylem)
 Plant fibers (Hemp,
flax)
 Cross section of Phaseolus (bean) seed
showing two layers of sclereids the seed
coat. The outer layer (actually the
epidermis) is composed of macrosclereids.
Cross section of Cannabis stem. Note
thick-walled fibers.
TISSUE SYSTEMS
Dermal tissue
 Protects
 Secretes waxy cuticle
Ground Tissue
 Photosynthetic
 Storage
Vascular Tissue
 Xylem – water transport toward leaves
 Phloem – sugar transport
 Found in “bundles” in all plant body parts
Vascular tissue organization
 Monocot Stem – vascular bundles
(combo of xylem and phloem) scattered
 Dicot stem – vascular bundles arranged
in a ring around the periphery
 Cross section of Helianthus (sunflower) stem with major tissues
labeled
Micrograph by Biodisc
Meristems
 def: perpetually embryonic tissues
 Indeterminate growth
 Primary growth lengthens roots and
shoots
 Secondary growth thickens roots and
shoots
Secondary Growth
Growth in girth
 Two lateral meristems (dicots):
 Vascular cambium
 Forms secondary xylem and phloem
 Secondary xylem accumulates (“wood”) while
secondary phloem is sloughed off
 Cork cambium
 Forms cork
 Bark=cork, cork cambium, and secondary phloem
TRANSPORT IN PLANTS
 Vascular Tissue
Xylem (review)
 Transports water and nutrients up from the
roots
 Dead at maturity
 Has thick secondary walls (often hardened with
lignin), supports the plant (this is wood…)
Phloem (review)
 Transports food from leaves to other
parts of the plant
Absorption by Roots (review)
 Root hairs increase surface area
 Mycorrhizae (mutualistic fungi) enhance
absorption
Long Distance Transport in the
Xylem
 Root Pressure: Pushing
 Transpiration: Pulling
Transpiration
 =pull of water toward leaves as water
molecules evaporate through stomata
 Major mechanism of movement
 Water is adhesive and cohesive
 As one water droplet moves, the next
also moves (water in continuous column
in xylem)
 As water evaporates out of the stomata,
water below moves upward
Stomata
What adaptations are seen for
arid climates?
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thick leaves (low SA/vol)
Thick cuticle
Stomata on lower leaf surface
Stomata in pores to shield wind
Shed leaves in hot dry season
Cacti have no leaves (adapt to spines)
Phloem Transport
Sugar moves from “sugar source to sugar sink”
Sugar loaded into phloem by active transport
Water follows by osmosis (increases pressure)
At sink, sugar leaves phloem (by diffusion or
active transport)
 Water follows (decreases pressure)
 Water is recycled by xylem
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Oleander:
stomata
in “cypts”
Old Man cactus
For what purposes do humans
use plants?