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Unit XI: Plant Structure and Function. Plant biology, perhaps the oldest branch of science, is driven by a combination of curiosity and need- curiosity about how plants work and a need to apply this knowledge judiciously to feed, clothe, and house a burgeoning human population.

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Unit XI: Plant Structure and Function


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unit xi plant structure and function

Unit XI: Plant Structure and Function

Plant biology, perhaps the oldest branch of science, is driven by a combination of curiosity and need- curiosity about how plants work and a need to apply this knowledge judiciously to feed, clothe, and house a burgeoning human population.

plant biology why
Plant Biology- Why?
  • Molecular Biology and Plant Biology
  • Arabidopsis thaliana
  • + weed that belongs to the mustard family
  • - organism of choice for molecular study
  • About Arabidopsis on the Internet

Genomic Sequence of 5 Chromosomes of Arabidopsis

evolution of plants

All Plants…

  • multicellular, eukaryotic, autotrophic, alternation of generations
Evolution of Plants
alternation of generations
Alternation of Generations
  • Sporophyte (diploid)
  • produces haploid
  • spores via meiosis
  • Gametophyte (haploid)
  • produce haploid
  • gametes via mitosis
  • Fertilization
  • joins two gametes to
  • form a zygote
angiosperms
Angiosperms
  • Monocots vs. Dicots
  • named for the number
  • of cotyledons present on
  • the embryo of the plant
  • + monocots
  • - orchids, palms,
  • lilies, grasses
  • + dicots
  • - roses, beans,
  • sunflowers, oaks
plant morphology
Plant Morphology
  • Morphology (body form)
  • shoot and root systems
  • + inhabit two environments
  • - shoot (aerial)
  • + stems, leaves, flowers
  • - root (subterranean)
  • + taproot, lateral roots
  • vascular tissues
  • + transport materials between
  • roots and shoots
  • - xylem/phloem
plant anatomy
Plant Anatomy
  • Anatomy (internal structure)
  • division of labor
  • + cells differing in structure and function
  • - parenchyma, collenchyma, sclerenchyma (below)
  • - water- and food-conducting cells (next slide)

Parenchyma

St: “typical” plant cells

Fu: perform most metabolic functions

Ex: fleshy tissue of most fruit

Collenchyma

St: unevenly thickened primary walls

Fu: provide support but allow growth

in young parts of plants

Ex: celery

Sclerenchyma

St: hardened secondary walls

Fu: specialized for support; dead

Ex: fibers (hemp/flax); slereids

(nut shells/seed coats)

water and food conducting cells
Water- and Food-conducting Cells
  • Xylem (water)
  • dead at functional maturity
  • tracheids- tapered with pits
  • vessel elements- regular tubes
  • Phloem (food)
  • alive at functional maturity
  • sieve-tube members- arranged
  • end to end with sieve plates
plant tissues
Plant Tissues
  • Three Tissue Systems
  • dermal tissue
  • + epidermis (skin)
  • - single layer of cells that
  • covers entire body
  • - waxy cuticle/root hairs
  • vascular tissue
  • + xylem and phloem
  • - transport and support
  • ground tissue
  • + mostly parenchyma
  • - occupies the space b/n
  • dermal/vascular tissue
  • - photosynthesis, storage,
  • support
plant growth

Meristems

  • perpetually embryonic tissues located at regions of growth
  • + divide to generate additional cells (initials and derivatives)
  • - apical meristems (primary growth- length)
  • + located at tips of roots and shoots
  • - lateral meristems (secondary growth- girth)
Plant Growth
primary growth of roots
Primary Growth of Roots
  • Primary Growth of Roots
  • apical meristem produces
  • all 3 tissue systems
  • + primary meristems
  • - protoderm
  • - ground meristem
  • - procambium
  • + root cap
  • + three overlapping zones
  • - cell division
  • - elongation
  • - maturation
primary growth in shoots
Primary Growth in Shoots
  • Primary Growth in Shoots
  • apical meristem (1, 7)
  • + cell division occurs
  • + produces primary meristems
  • - protoderm (4, 8)
  • - procambium (3, 10)
  • - ground meristem (5, 9)
  • axillary bud meristems
  • + located at base of
  • leaf primordia
  • leaf primordium (2, 6)
  • + gives rise to leaves
leaf anatomy
Leaf Anatomy
  • Epidermal Tissue
  • upper/lower epidermis
  • guard cells (stomata)
  • Ground Tissue
  • mesophyll
  • +palisade/spongy
  • parenchyma
  • Vascular Tissue
  • veins
  • + xylem and phloem
secondary growth
Secondary Growth
  • Lateral Meristems
  • vascular cambium
  • + produces secondary xylem/phloem (vascular tissue)
  • cork cambium
  • + produces tough, thick covering (replaces epidermis)
  • secondary growth
  • + occurs in all gymnosperms; most dicot angiosperms
vascular cambium
Vascular Cambium
  • Production of Secondary Vascular Tissue
  • Vascular Cambium cells give rise to xylem (X) and phloem (P)
  • + Cambium cell (C) gives rise to initial and derivative (D)
  • - Derivative differentiates into xylem (X) or phloem (P) cell
cork cambium
Cork Cambium
  • Periderm
  • protective coat of
  • secondary plant body
  • + cork cambium and
  • dead cork cells
  • - bark
  • cork cambium produces
  • cork cells
  • + cork cells deposit
  • suberin and die
  • secondary growth
  • commences farther down
  • the shoot
  • + transforms older
  • regions first
plant nutrition
Plant Nutrition
  • What does a plant need to survive?
  • 9 macronutrients, 8 micronutrients
  • + macro- required in large quantities
  • - C, H, N, O, P, S, K, Ca, Mg
  • + micro- required in small quantities
  • - Fe, Cl, Cu, Mn, Zn, Mo, B, Ni
  • + usually serve as cofactors
  • of enzymatic reactions
mineral deficiency
Mineral Deficiency
  • Mineral deficiency
  • symptoms related to function of element
  • + Mg- causes chlorosis
  • - ingredient of chlorophyll
  • + Fe- causes chlorosis
  • - required as cofactor in photosynthesis
  • symptoms also related to mobility of element
  • + Mg- chlorosis of older leaves
  • - relatively mobile
  • + Fe- chlorosis of younger leaves
  • - relatively immobile
  • + young, growing tissues have more
  • “drawing power”
  • hydroponic culture
  • + growing plants by bathing roots- no soil!
slide20
Soil
  • Texture and Composition
  • texture depends on size of particles
  • + sand-silt-clay
  • - loams: equal amounts of sand,
  • silt, clay
  • composition
  • + horizons
  • - living organic matter
  • - A horizon: topsoil, living
  • organisms, humus
  • - B horizon: less organic, less
  • weathering than A horizon
  • - C Horizon: “parent” material
  • for upper layers
  • soil conservation issues
  • + fertilizers, irrigation, erosion
nitrogen

Soil Bacteria

  • decompose humus to release nitrogen in soil
  • + plants absorb ammonium (NH4+), nitrate (NO3-)
  • - nitrogen-fixing bacteria
  • - ammonifying bacteria
  • - nitrifying bacteria
Nitrogen
nutritional adaptations
Nutritional Adaptations
  • Symbiotic Relationships
  • symbiotic nitrogen fixation
  • + root nodules contain bacteroids (Rhizobium bacteria)
  • - mutualistic relationship
  • mycorrhizae
  • + symbiotic associations of fungi and roots
  • - mutualistic relationship
  • + ectomycorrhizae
  • - mycelium forms mantle over root
  • + endomycorrhizae
  • - does not form mantle; hyphae extend inward
  • parasitic plants
  • + plants that supplement their nutrition from host
  • - mistletoe, dodder plant, Indian pipe
  • carnivorous plants
  • + supplement nutrition by digesting animals
transport in plants
Transport in Plants
  • Transport
  • occurs on three levels
  • + cellular level
  • - absorption of water/minerals
  • from soil by root cells
  • + short-distance transport
  • - cell to cell at tissue/organ level
  • + loading of sugar from
  • photosynthetic cells to phloem
  • + long-distance transport
  • - sap within xylem and phloem
  • throughout plant
absorption of water and minerals by roots
Absorption of Water and Minerals by Roots

soil --> epidermis --> root cortex --> xylem

uptake of soil solution
Uptake of Soil Solution
  • Symplastic Route
  • continuum of cytosol based
  • on plasmodesmata
  • Apoplastic Route
  • continuum of cell walls and
  • extracellular spaces

Lateral transport of soil

solution alternates between

apoplastic and symplastic

routes until it reaches the

Casparian strip

Mycorrhizae

casparian strip
Casparian Strip

The Casparian strip is a belt

of suberin (purple) that

blocks the passage of water

and dissolved minerals.

Only minerals that are already

in the symplast or enter that

pathway by crossing the

plasma membrane can detour

around the Casparian strip and

pass into the stele.

Summary of uptake

of soil animation

transport of xylem sap
Transport of Xylem Sap
  • Transpiration
  • the loss of water vapor from leaves and other aerial parts of the plant
  • + transpirational pull
  • - transpiration-cohesion-tension mechanism

Water vapor diffuses from the moist

air spaces of the leaf to the drier air

outside via stomata.

Tension is created by the evaporation

of water and pulls water from

locations where hydrostatic pressure

is greater (xylem).

Transpirational pull draws water out

of xylem and through mesophyll

tissue to the surfaces near stomata.

cohesion and adhesion of water
Cohesion and Adhesion of Water
  • Hydrogen Bonding
  • cohesion
  • + water molecules tug on to each other
  • adhesion
  • + water molecules adhering to the
  • hydrophillic walls of xylem cells
control of transpiration
Control of Transpiration
  • Photosynthesis-Transpiration Compromise
  • guard cells help balance plant’s need to conserve water with its
  • requirement for photosynthesis
  • + stomata open (widen) and
  • close (narrow)
  • - guard cells change their
  • shape (turgid/flaccid)
  • - reversible uptake/loss of
  • potassium (K+) ions
translocation of phloem sap
Translocation of Phloem Sap
  • Source to Sink
  • sugar source
  • + organ that produces sugar
  • sugar sink
  • + organ that consumes/stores sugar
  • phloem loading and unloading
  • + chemiosmotic mechanism
  • actively transports sucrose
  • - sucrose is co-transported with
  • H+ back into cell
plant reproduction
Plant Reproduction
  • Sporophyte (diploid)
  • produces haploid
  • spores via meiosis
  • Gametophyte (haploid)
  • produce haploid
  • gametes via mitosis
  • Fertilization
  • joins two gametes to
  • form a zygote
angiosperm life cycle
Angiosperm Life Cycle
  • Sporophyte (diploid)
  • actual plant with
  • flowers
  • Gametophyte (haploid)
  • male: germinated
  • pollen grain
  • female: embryo sac
  • Fertilization
  • joins two gametes to
  • form a zygote
moss life cycle
Moss Life Cycle
  • Gametophyte
  • dominant generation
  • + has both sexes and
  • produces gametes
  • - archegonia (eggs)
  • - antheridia (sperm)
  • Fertilization
  • sperm move along moss to
  • find archegonia
  • Sporophyte
  • grows on top of gametophyte
  • + sporangia is where spores
  • are produced by meiosis
fern life cycle
Fern Life Cycle
  • Sporophyte
  • produce spores via
  • meiosis
  • + spores develop
  • into young
  • gametophyte
  • Gametophyte
  • has both sexes and
  • produces gametes
  • - archegonia
  • (eggs)
  • - antheridia
  • (sperm)
  • Fertilization
  • similar to mosses
gymnosperm life cycle
Gymnosperm Life Cycle
  • Sporophyte
  • produce gametophytes inside
  • of cones
  • + Pollen cone (male)
  • - produces microspores
  • via meiosis
  • + Ovulate cone (female)
  • - produces megaspores
  • via meiosis
  • Fertilization
  • pollen grains discharge sperm
  • into egg
male and female gametophyte of flowering plant
Male and Female Gametophyte of Flowering Plant
  • Male Gametophyte
  • pollen grain
  • + microspores produced
  • within the anther
  • + divide once to
  • produce two
  • sperm cells
  • Female Gametophyte
  • embryo sac
  • + megaspore produced
  • within the ovule
  • + divide to produce
  • three egg cells
  • - 2 polar nuclei
double fertilization
Double Fertilization
  • Double Fertilization
  • pollen grain lands on stigma
  • + pollen tube toward ovule
  • + both sperm discharged down the tube
  • - egg and one of the sperm
  • produce zygote
  • - 2 polar nuclei and sperm
  • cell produce endosperm
  • + ovule becomes the seed coat
  • + ovary becomes the fruit