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?