ch. 39 pt. 2 Flashcards
auxin acronym
ELF TV FAD GP
- elongation, leaf venation, fruit development, tropism, vascular cambium, female gametophyte organization, adventitious roots, apical dominance, gene expression, phyllotaxy
cytokinins acronym
DDANG
- division, apical dominance, anti-aging, nutrients to sinks, germination of seed
gibberellins acronym
GEFS JP
- germination, elongation, fruit development, sex determination, juvenile to adult, pollen development/tube
abscisic acid acronym
SSDD
- slows growth, stomatal closure, seed dormancy, drought tolerance
ethylene acronym
SSHAF
- stress, senescence, leaf abscission, fruit ripening
what are some of effects of gibberellins
- stem elongation
- fruit development
- seed germination
where are gibberellins produced?
in young roots and leaves
how do gibberellins stimulate the growth of leaves/stems?
enhancing cell elongation and cell division
bolting
rapid growth of the floral stalk induced by gibberellins
hormones necessary for fruit development
auxin and gibberellins
what signals the seed to germinate?
release of gibberellins from the embryo after water is imbibed
how does abscisic acid slow growth?
antagonizing actions of growth hormones
what does seed dormancy increase the likelihood of
that a seed will germinate only in optimal condiitons
when do many dormant seeds germinate?
when ABA is removed/inactivated
what affects whether seeds will break dormancy?
ratio of ABA to gibberellins
what can precocious (early germination be caused by
inactive or low levels of ABA
what happens when ABA accumulates in leaves?
stomata close rapidly
early warning system
transport of ABA from water-stressed root systems to leaves
abiotic stress
heat, cold, drought, salt, metals, flooding
- primary metabolites
- plant development
biotic stress
pathogen attack, insect attack, herbivore attack
- phytohormones
- plant defense
when is ethylene produced?
when the plant experiences stress
- drought, flooding, mechanical pressure, injury, infection
effects of ethylene
- senescence
- leaf abscission
- fruit ripening
triple response to mechanical stress
- ethylene produced when seedling tip pushes against obstacle
- stem elongation slowed, stem thickens, stem grows horizontally
- vertical growth resumes when effects wear off
senescence
programmed death of certain cells/organs/plants
- burst of ethylene associated with onset of apoptosis
leaf abscission
change in balance of auxin and ethylene stimulates process of leaf falling (autumn)
what happens when ethylene triggers fruit ripening
ripening triggers more relate of ethylene
how can fruit produces control ripening
by picking green fruit and controlling ethylene levels
photomorphogenesis
response to light
what qualities of light to plants detect?
presence, direction, intensity, wavelength (color)
2 major classes of light receptors
- blue-light photoreceptors
- phytochromes
what plant responses does blue light initiate?
- hypocotyl elongation
- stomatal opening
- phototropism
phototropin
protein kinase involved in mediating plant responses to blue light
phytochromes
pigments that regulate many of plant’s responses to light throughout its life
what are phytochrome responsible for?
- de-etiolation
- seed germination
- shade avoidance
when do seeds remain dormant until?
until light and other conditions are near optimal
effects of red light
increase germination
- activates phytochrome
effects of far-red light
inhibits germination
- inactivates phytochrome
are the effects of red and far-red light reversible?
yes
what kind of light exposure determines the response
final
what 2 states do phytochrome exist in?
2 photoreversible states: P(r) to P(fr) triggers developmental repsonses
what conversion does red light trigger?
P(r) to P(fr) - faster
Pr is inactive, Pfr is active
what conversion does far-red light trigger?
P(fr) to P(r) - slower
what does sunlight increase the ratio of?
P(fr) to P(r)
- contains both red and far-red light
- triggers germination
what do leaves in a canopy absorb?
red light, allow far-red light to pass through to shaded plants below
shade avoidance
when a tree is shade, the phytochrome ratio shifts in favor of P(r), inducing vertical growth
what do plant processes oscillate during the day in response to?
light and temperature changes
what do many processes oscillate with a frequency of?
24 hours
- even under constant environmental conditions
photoperiod
relative lengths of night and day
- environmental stimulus plants use to detect time of year
photoperiodism
physiological response to photoperiod
different flowering photoperiod plants
- short-day
- long-day
- day-neutral
short-day plants
plants that flower when a light period is shorter than a critical length
long-day plants
plants that flower when a light period is longer than a certain number of hours
day-neutral plants
controlled by plant maturity, not photoperiodf
is flowering controlled by night length or day length
night length
what are short-day plants governed by
whether critical night length sets a minimum number of hours of darkness
what are long-day plants governed by
whether critical night length sets maximum number of hours of darkness
gravitropsim
response to gravity
what kind of gravitropism do roots show
positive
what kind of gravitropism do shoots show
negative
statoliths
dense cytoplasmic components settle in response to gravity
thigmomorphogenesis
changes in form that result from mechanical disturbance
thigmotropism
growth in response to touch
where does thigmotropism occur
vines and other climbing plants
what does the touch response result from
action potentials - transmission of electrical impulses
what happens when water loss by transpiration exceeds water absorption?
plants may wilt or die
how do plants reduce transpiration during drought?
- closing stomata
- reducing exposed surface area
- shedding leaves
what does waterlogged soil lack?
the air spaces needed to provide oxygen for cellular respiration in roots
what does the enzymatic destruction of root cortex cells create?
air tubes that help plants survive oxygen deprivation during flooding
what do some plants, like mangroves, produce in response to flooding?
aerial roots
salt and water potential of soil
- lower water potential of soil and reduces water uptake
how to plants respond to salt stress?
producing solutes tolerated at high concentrations
- keeps water potential of cells more negative than that of soil solution
what does excessive heat do to a plant’s enzymes?
denature them
how does transpiration cool leaves?
evaporative cooling
heat-shock proteins
proteins produced at temperatures above 40 degrees C to help protect other proteins from heat stress
what do cold temperatures do to plants
- decrease membrane fluidity
- alter lipid composition of membranes
what does ice formation do to water potential?
reduces water potential outside cell
in frost-tolerant species, how do plants reduce water loss from the cell?
increase solute concentration of cytoplasm
antifreeze proteins
hinder formation of ice crystals
why to plants use defense systems?
to deter herbivory, prevent infection, combat pathogens
