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Plant Structure and GrowthPlant Structure and Growth
Chapter 35Chapter 35
Monocots vs. dicotsMonocots vs. dicotsPage 595
Monocot or Dicot?Monocot or Dicot?
Monocot or Dicot?Monocot or Dicot?
Monocot or Dicot?Monocot or Dicot?
Monocot or Dicot?Monocot or Dicot?
Annuals vs. perennialsAnnuals vs. perennials
AnnualsAnnuals live for a year live for a year Examples??Examples??
PerennialsPerennials live for several years live for several years Examples??Examples??
PLANT BODY PARTSPLANT BODY PARTS
RootsRoots Fibrous Root systemsFibrous Root systems
MonocotsMonocots Anchor plants Anchor plants Prevent erosionPrevent erosion Increases surface area for absorption of Increases surface area for absorption of
water and nutrientswater and nutrients
Taproot SystemsTaproot Systems
DicotsDicots Anchor plants Anchor plants Stores food Stores food
Carrots, turnips, sugar beetsCarrots, turnips, sugar beets
Can go far below groundCan go far below ground Desert plantsDesert plants
Root HairsRoot Hairs
Epidermal Epidermal extensionsextensions
Increase surface Increase surface areaarea
Symbiosis with fungiSymbiosis with fungi
Most plants have mutualistic partnership Most plants have mutualistic partnership with fungi forming a root/fungus structure with fungi forming a root/fungus structure called called mycorrhizaemycorrhizae
Fungi absorb water and select minerals Fungi absorb water and select minerals for host plant (HUGE surface area)for host plant (HUGE surface area)
Host plant nourishes fungusHost plant nourishes fungus
StemsStems SupportSupport transporttransport
LeavesLeaves Typical leavesTypical leaves
Flattened bladesFlattened blades Petioles – join leaf to the stem nodePetioles – join leaf to the stem node
Specialized leaves to reduce water loss?Specialized leaves to reduce water loss? Specialized leaves to store water?Specialized leaves to store water?
CELL TYPESCELL TYPES
ParenchymaParenchyma
Most abundant typeMost abundant type ““typical” plant celltypical” plant cell Thin cell wallsThin cell walls Most photosynthetic Most photosynthetic
and storage tissue, and storage tissue, phloem, fruit tissuephloem, fruit tissue
Starch grains from Starch grains from potato tuber, potato tuber, stained with Istained with I22KI.KI.
Cross section of Cross section of PhormiumPhormium (New Zeland flax) leaf. (New Zeland flax) leaf. Note large areas of supporting fibers and thin-walled Note large areas of supporting fibers and thin-walled parenchyma cells that function in water storage.parenchyma cells that function in water storage.
CollenchymaCollenchyma Thicker cell wallsThicker cell walls Provides support for Provides support for
young shoot, petiolesyoung shoot, petioles
SclerenchymaSclerenchyma
SupportsSupports Thickest cell wallsThickest cell walls May be dead at May be dead at
maturity (xylem)maturity (xylem) Plant fibers (Hemp, Plant fibers (Hemp,
flax)flax)
Cross section of Cross section of PhaseolusPhaseolus (bean) seed (bean) seed showing two layers of sclereids the seed showing two layers of sclereids the seed coat. The outer layer (actually the coat. The outer layer (actually the epidermis) is composed of macrosclereids.epidermis) is composed of macrosclereids.
Cross section of Cannabis stem. Note thick-walled fibers.
TISSUE SYSTEMSTISSUE SYSTEMS
DermalDermal tissue tissue
ProtectsProtects Secretes waxy Secretes waxy cuticlecuticle
GroundGround Tissue Tissue
PhotosyntheticPhotosynthetic StorageStorage
VascularVascular Tissue Tissue
Xylem – Xylem – waterwater transport toward leaves transport toward leaves Phloem – Phloem – sugarsugar transport transport Found in “bundles” in all plant body partsFound in “bundles” in all plant body parts
Vascular tissue organizationVascular tissue organization
Monocot Stem – vascular bundles Monocot Stem – vascular bundles (combo of xylem and phloem) scattered(combo of xylem and phloem) scattered
Dicot stem – vascular bundles arranged Dicot stem – vascular bundles arranged in a ring around the peripheryin a ring around the periphery
Cross section of Cross section of HelianthusHelianthus (sunflower) stem with major tissues (sunflower) stem with major tissues labeledlabeledMicrograph by BiodiscMicrograph by Biodisc
MeristemsMeristems def: perpetually embryonic tissuesdef: perpetually embryonic tissues Indeterminate growthIndeterminate growth Primary growth lengthens roots and Primary growth lengthens roots and
shootsshoots Secondary growth thickens roots and Secondary growth thickens roots and
shootsshoots
Secondary GrowthSecondary GrowthGrowth in girthGrowth in girth Two lateral meristems (dicots):Two lateral meristems (dicots):
Vascular cambiumVascular cambium Forms secondary xylem and phloemForms secondary xylem and phloem Secondary xylem accumulates (“wood”) while Secondary xylem accumulates (“wood”) while
secondary phloem is sloughed offsecondary phloem is sloughed off
Cork cambiumCork cambium Forms corkForms cork Bark=cork, cork cambium, and secondary phloemBark=cork, cork cambium, and secondary phloem
TRANSPORT IN PLANTSTRANSPORT IN PLANTS
Vascular TissueVascular Tissue
Xylem (review)Xylem (review) Transports water and nutrients up from the Transports water and nutrients up from the
rootsroots Dead at maturityDead at maturity Has thick secondary walls (often hardened with Has thick secondary walls (often hardened with
lignin), supports the plant (this is wood…)lignin), supports the plant (this is wood…)
Phloem (review)Phloem (review) Transports food from leaves to other Transports food from leaves to other
parts of the plantparts of the plant
Absorption by Roots (review)Absorption by Roots (review)
Root hairs increase surface areaRoot hairs increase surface area Mycorrhizae (mutualistic fungi) enhance Mycorrhizae (mutualistic fungi) enhance
absorptionabsorption
Long Distance Transport in the Long Distance Transport in the XylemXylem
Root Pressure: PushingRoot Pressure: Pushing Transpiration: PullingTranspiration: Pulling
TranspirationTranspiration =pull of water toward leaves as water =pull of water toward leaves as water
molecules evaporate through stomatamolecules evaporate through stomata Major mechanism of movementMajor mechanism of movement Water is adhesive and cohesiveWater is adhesive and cohesive As one water droplet moves, the next As one water droplet moves, the next
also moves (water in continuous column also moves (water in continuous column in xylem)in xylem)
As water evaporates out of the stomata, As water evaporates out of the stomata, water below moves upwardwater below moves upward
StomataStomata
What adaptations are seen for What adaptations are seen for arid climates?arid climates?
thick leaves (low SA/vol)thick leaves (low SA/vol) Thick cuticleThick cuticle Stomata on lower leaf surfaceStomata on lower leaf surface Stomata in pores to shield wind Shed leaves in hot dry seasonShed leaves in hot dry season Cacti have no leaves (adapt to spines)
Phloem TransportPhloem Transport
Sugar moves from “sugar source to sugar sink”Sugar moves from “sugar source to sugar sink” Sugar loaded into phloem by active transportSugar loaded into phloem by active transport Water follows by osmosis (increases pressure)Water follows by osmosis (increases pressure) At sink, sugar leaves phloem (by diffusion or At sink, sugar leaves phloem (by diffusion or
active transport)active transport) Water follows (decreases pressure)Water follows (decreases pressure) Water is recycled by xylemWater is recycled by xylem
Oleander: stomata in “cypts”
Old Man cactus
For what purposes do humans For what purposes do humans use plants?use plants?