Temperature 

Environmental Cue

Bud hardening

Gradual exposure to low temperatures prepares bud for freezing

Seed dormancy

Many seeds require minumum number of cold hours to germinate

Flowering

Fruit trees flower & set fruit only after recieving cold treatment

Plant response to gravity

Negative

-opposite direction of gravity

Positive

-direction of gravity

Day Neutral Plants

=DNPs

Root tips

Stem tips

Leaf tips

Fruits

Flowers

Pollen

Embryos

Growth in response to light

IAA accumulates on dark side

Plant bends towards light

Maximize photosynthesis

Dark side elongates faster than light side

Growth in response to gravity

Stems bend away from gravity

-negative geotropic response

Lower side of stem grows faster than upper side

Stem bends upward

Growth in response to gravity

Roots bend toward gravity

-positive geotropic response

IAA & ABA interact to cause downward growth

IAA accumulates on upper side to stimulate cell elongation

ABA accumulates on lower side to inhibit cell elongation

Roots grow downward

IAA causes dedifferentiation of stem cells & redevelopment as root cells

Roots may grow from unexpected places eg. aerial stem

IAA used to initiate root growth

Stem cuttings

Tissue culture

A series of reactions leading to cell death

Leaf/Fruit Drop

Programmed Cell Death

Repair to "wound" site to prevent infection & loss of plant sap

Leaf drop results from the action of 3 hormones;

Auxin (IAA)

Ethylene (C2H4)

Abscisic Acid (ABA)

GA Deficiency

-Defective GA biosynthetic pathway

-Rescues by exogenous GA application

GA Insensitivity

-Defective GA receptor/signaling cascade

-Not rescue by exogenous GA application

Sudden increase in internode length

-Occurs in dark-grown seedlings

-Initiate flowering

Rosette forming plants

-Extremely short internodes so leaves appear to be arranged like petals on rose

-Bolt after cold-hour threshold exceeded

-Internodes elongate

-Tall spike with flowers at tip develop

After cold-threshold exceeded

-Threshold = hours below 40 degrees farenheit

-Gibberellin levels increase

-Promotes growth & breaks dormancy

-Warmer temperatures accelerate enzyme activities

Unicell 

(Algal Body Types)

Colony

(Algal Body Types)

Filament

(Algal Body Types)

Pseudoparenchyma

(Algal Body Types)

Cells joined in 2 or 3 dimensions to form an apparent tissue

Formed among seaweeds

Unbranched filament

Capable of nitrogen fixation: N2->NH4

Asexual reproduction

-Forms hormongonia and seperation disks

-Divides by binary fission

Moves by contraction

Musilage for attachment

Filament

Non-motile

Fragmentation (asexual reproduction)

No muscilage

Heterocyst

Thick walls

Nitrogen fixation

PSI only (no O2 production)

Symbiotic association with Azolla (water fern)

Anabaena in intercellular spaces of Azolla

Colony

-Aggregate of cells in muscilage sheath

-2n cells: usually 8 or 16

-Cells in rows

Motile = flagella

-Tumbling/rolling motion

Cup-shaped chloroplasts

-Less evolved than Volvox

Colony (2n cells)

Hollow sphere

Motile (2 flagella per vegetative cell)

Forms daughter colonies at center of sphere

-Same number of cells as parent colony

-Reproductive cells; Asexual, Sexual

Chlamydomonas-like cells

Cup-shaped chloroplasts

Found in freshwater

Colony

-2n cells: usually 4 cells

Non-motile: floater

Wall spines

-Cell wall material

Cup-shaped chloroplasts

Found in fresh or brackish water

Unbranched filament

Ribbon-shaped chloroplasts that forms a pariental spiral

Sexual reproduction by conjugation

Planktonic

Pyrenoid

-Starch grain

-Rubisco crystals

Freshwater

Desmid-two discernable halves

Unicell

-Almost looks like 2 cells

-Connected by ismus

2 chloroplasts

Pyrenoid

-Starch storage

-Rubisco protein

Zygospore survives adverse conditions

Colony

-1 cell thick

-Snowflake appearance

2n=usually 16 cells

Cells different shape (edge v center)

Benthic bottom dweller

When growing on soil or agar the algae is non-motile & grows in gelatinous colonies

When flooded, motile unicells form

Widely distributed in freshwater, especially where N is abundant

Euglenaphyta:

Unicell or colony

Food storage=paramylon

Pellicle=no cellulose in cell wall

Chlorophylls a & b

Euglena:

Unicell

Motile: 1 flagella

Red eye spot

Changes shape

Prefers high NH3

Bivalves

Gliding movement

Muscilage

Cell wall with 2 overlapping pieces, much like a petri plate

cell wall contains silica

Diatoms rich in fossil record

-glass walls do not biodegrade

Cell wall highly ornamented

Diatoms deposits

Mined for commercial uses

Uses of diatomaceous earth:

Toothpaste

Silver polish

Insulation

Filters (pool, water)

Pesticides

Abrasives

Dinoflagellate

Armor-plated

Large vacuole

Unicell

2 flagella propel cell

Pyrrhophyta

-Other dinoflagellate genera are associated with red tide & paralytic shellfish poisoning

Endotoxins

Symbiotic with corals

Major Divisions of Algae

Correct names with colors

Cyanophyta = Blue-green

Chlorophyta = Green

Chrysophyta = Golden brown

Rhodophyta = Red

Phaeophyta = Brown

Shoot Growth

Root Growth

less IAA more CK

More IAA less CK

Extracted from brown seaweeds

Used as emulsifying agent in processed foods

Extracted from red algae

Used in medicines and microbiological media

Blue-Green Algae

Prokaryotes

Photosynthetic pigments dispersed throuhgout cells

Capable of nitrogen fixation

Other Algae

Eukaryotes

Photosynthetic pigments localized in chloroplasts

IAA = Indole-3-acetic acid 

naturally occuring

2,4-D = 2,4-Dichlorophenoxyacetic acid

Man-made mimic of IAA

Root tips

Stem tips

Leaf tips

Fruits

Flowers

Pollen

Embryos

Cell enlargement

Tropism

Apical Dominance

Adventitious rooting

Senescence

Coleoptile grows toward light source by faster elongation of cells on dark side than on lighted side

Removal of coleoptile tip inhibits curvature

Covering coleoptile tip inhibits curvature

Light is percieved in the tip and signal is transmitted to elongation zone

Boysen-Jensen Experiment (1913)

Mica sheet

Partial insertion of mica into dark side of coleoptile inhibits curvature

Partial insertion of mica into lighted side of coleoptile does not inhibit curvature

Light stimulation is transmitted from tip to elongation zone

Boysen-Jensen (1913)

Gelatin

Insertion of gelatin block between tip and coleoptile yields curvature response

Light stimulation able to be transmitted by a diffusable chemical substance

Excised tip asymmetrically on coleoptile yields curvature

Growth stimulus is a diffusable chemical substance

Gelatin block induces curvature without light stimulus

Degree of curvature correlated with amount of coleoptiles on gelatin

IAA travels down dark side of stem in unilateral light

IAA accumulates on lower side of stem in response to gravity

IAA activates expansins by altering pH of cell wall

Expansins weaken cellulose bonds; elastic cell walls

Turgor pressure stretchs cell walls

Auxin induces gene expression of expansins

mRNA for expansins transcribed in nucleus

mRNA moves to cytoplasm

mRNA translated into expansin protein

Expansins aid cellular enlargement

Activation of gene expression

Gene expression increases number of expansin proteins in cell wall that break bonds in cell in cell wall to allow cell expansion

mRNA,Protein, and Enzyme activity in tissue increase

Ethylene activates pectinase

pectinase breaks down the middle lamella

forms abscision layer

cell no longer held together strongly

wind causes petiole to sperate from stem

Ethylene must overpower Auxin

After cold-threshold exceeded ( below 40 degrees celcius)

Activation of amylase

converts starch in endosperm to sugars

Required by embryo for nutrition

Increase plant size

Maling beer

Counteract GA

Used to create dwarf plants

Used to reduce internode length

Promotes vascular tissue development

Promote shoot initiation

Delays leaf senesence

Anti-viral agent

In combination with IAA, promotes callus formation

Induces callus to form shoots

Gas, accumulates in intercellular spaces

Production stimulated by motion, shaking, wind

Abscission-C2H4 inhibits IAA transport

Fruit Ripening-C2H4 causes changes in fruit

Inhibits Seed germination

COntrols Plasmodesmata permeability

Stomatal regulation-ABA accumulates in response to drought, closed stomates

Senesence-initiates cork formation

Cell elongation inhibitor in roots

Gravitropism

Active agent: Glyphosate

Blocks synthesis of aromatic amino acids

Stops protein synthesis and plant dies

Not toxic to animals

Active agents: 2, 4-D/ 2.4.5-T

Plugs phloem at sieve plates

Plant dies because food cannot be transported to non-photosynthetic tissues

Mutagenic

Causes breaks in DNA which lead to alteration and loss of gene function