Gas exchange Photosynthesis

Phloem –sugar transport

Gas exchange –cellular respirationWater & mineral

absorption

Xylem – water & mineral transport

Transpiration

3 MAIN CELL COMPARTMENTS

TISSUE COMPARTMENTS•Symplast – travel via cytosol continum

•Apoplast- travel via cell walls& extracellular spaces

ABSORPTION OF WATER& MINERALS BY ROOTS

Mycorrhizae –•Symbiotic relationship•Surface area for absorption

TRANSPORT OF WATER

• Root pressure

• Guttation

• Transpirational pull

• Cohesion & adhesion

TRANSPIRATIONAL PULL

ASCENT OF WATER

•SOLAR POWERED

•HYDROGEN BONDING

•CHARACTERISTICS OF WATER

CONTROL OF TRANSPIRATION

Photosynthesis – transpiration compromiseGuard cellsStomaopen

Stomaclosed

Guard cells:inner walls thicker, cellulose microfibrils

Guard cells: regulated by uptake and loss of K+

Adaptations to reduce transpiration:thick cuticle, recessed stomata

Stoma

TRANSLOCATION OF PHLOEM SAP

From source (sugar production) to sink (consumes or stores sugar), pressure flow hypothesis

Chemiosmotic mechanism for active transport of sucrose

PRESSURE FLOWLoading of sugar reduces water potential

Absorption of water generates pressure and forces flow

Pressure gradient reinforced by the unloading of sugar at the sink

Xylem recycles water from sink to source

Tapping phloem-sap with the help of an aphid

THE AVAILABILITY OF SOIL WATER & MINERALS

• Roots hairs increase surface area• Minerals actively transported in, water follows by osmosis

Soil Bacteria:Nitrogen fixing & Ammonifying

(decomposers)

Root nodules on legumes

Development of a soybean root nodulePericycle layer gives rise

to secondary roots

PARASITIC PLANT

CARNIVOROUS PLANTS

ANGIOSPERM LIFE CYCLEsporophyte/gametophyte;

diploid/haploid

FLOWER ANATOMYComplete-all organsIncomplete-lacking

1 or more organsBisexual – both

stamens & carpelsUnisexual-one or the

otherMonoecious-

carpellate & staminate flowers

Dioecious-separate plants

Angiosperm Gametophytes

Pollen grains

male

female

Reduce self - fertilization

Genetic Basis of Self-Incompatibility

Growth of pollen tube and double fertilization

*

*

Development of a Dicot Embryo

Below cotyledons

Above cotyledons

Embryonic root

Unique to monocots

Development 0f a pea fruit

GERMINATION• Imbibition• Release of Gibberellic acid• Aleurone enzymes (α amylase)• Hydrolysis of endosperm

Seed Germination- Radicle emerges 1st

a) Cotyledons pulled from soilb) Hypocotyl emerges, cotyledons remain in groundc) Shoot grows up through coleoptile

ASEXUAL REPRODUCTION(vegetative reproduction)

Fragmentation – separation of a parent plant into parts that reform whole plants

Root system of a single parent gives rise to many adventitious shoots

Vegetative Propagation- cuttings

PLANT RESPONSES TO EXTERNAL SIGNALS

Light induced greening of dark sprouted potatoes

Grass seedlinggrowing towardlight

Signal Transduction Pathway(review)

TROPISMS

• Phototropism – response to light– Stems (positive); Roots (negative)

• Gravitropism – response to gravity– Stems (negative); Roots (positive)

• Thigmotropism – response to contact– Curling around objects (vines)

PHOTOTROPISM

CONCLUSION

-CHEMICAL SIGNALPRESENT IN COLEOPTILE TIP STIMULATES GROWTHAS IT PASSED DOWN THECOLEOPTILE-HIGHER CONCENTRATIONOF CHEMICAL ON DARKER SIDE CAUSED THE PLANT GROWTH TO CURVE TOWARD LIGHT- NAMED THE CHEMICAL “AUXIN”

PLANT HORMONES• Auxins – stem elongation in apical

meristems– Fruit maturation, prevents abscission

• Cytokinins – cell division in roots, embryos, fruits

• Gibberellins – stem elongation in mature regions, fruit development

• Abscisic acid – dormancy, stress, abscission

• Ethylene – fruit ripening

Apical Dominance:•Terminal shoot inhibits lateral buds•Auxin responsible

Gibberellins:•Stimulate growth (elongation & division)•Tall spindly plants•Larger seedless grapes

Abscisic Acid (ABA)•Seed dormancy

-Inhibits germination•Stress

-Drought-Winter

Leaf Abscisision

•Parenchyma cells w/ very thin walls

•Change in balanceof auxin & ethylene

•Aging leaf producesless & less auxin

Phytochrome regulation of lettuce seeds

Pr ↔ Pfr acts as a switching mechanismthat controls various light-induced events

Links light reception to cellular responses

Functions as the photoreceptor

bluish blue-greenish

Switched on by

Photoperiodic Control of Flowering

Short day plants flower when night exceeds the critical dark period

Long day plants flower when night is shorter than the critical dark period

Root Gravitropism

Smaller plant touched 2x/day

Rapid turgor movements

Response to flooding & oxygen deprivation