Plant Hormones and Tropisms Pt. 2 Flashcards
unequal growth due to contact with solid objects
thigmotropism
Greek words for thigmotropism
Thigma, tropos
Thigma means
touch
example of thigmotropism
coiling of tendril
grows straight until it touches something, then the cells in contact with an object, grow less while those on the opposite side elongate
flowering plant
can be quite rapid; a tendril has been observed to encircle an object within 10 minutes
thigmotropism
can bring about a response that lasts for several days
thigmotropism
thigmotropism can be delayed in the dark, and this will only respond when illuminated
tendrils
after the transfer of a phosphate group from ATP to the photoreceptor, what happens to the photoreceptor
triggers a transduction pathway, in some unknown way, leads to the entry of auxin into the cell
rather than light can cause thigmotropism, therefore the need for light may simply be a need for ATP
adenosine triphosphate (ATP)
touch response related to thigmotropism but the entire plant responds to the presence of environmental stimuli, such as wind or rain
thigmorphogenesis
what happens to a tree growing in a windy location
shorter, thicker trunk
such as rubbing a plant with a stick can inhibit cellular elongation a produce a sturdier plant with increased amounts of support tissue
mechanical simulation
dependent on turgor pressure changes in plant cells
turgor movements
do not involve growth and are not related to the source of the stimulus
turgor movements
turgor movements can result from
touch
shaking
thermal simulation
a sensitive plant which has compound leaves, meaning that each leaf contains many leaflets
mimosa pudica (makahiya)
has a progressive response to the stimulus that takes only a second or two
mimosa
thickening, a portion of flowering plant that is involved in controlling turgor movement
pulvinus
lose potassium ions and then water follows by osmosis that causes the leaf folding
motor cells
what happens to the leaflets of the leaf when the pulvinus cells lose turgor
collapse
cause the response to move from one leaflet to another after a leaflet collapse
electrical mechanism
speed of electrical charge measured and its transmission
1 cm/s
closes its trap in less than 1 second when three hairs at the base of the trap (trigger hairs) are touched by an insect
venus flytrap
where the electrical charge is propagated in venus flytrap
lobes of the leaf
what causes the electrical charge that is propagated in the venus flytrap (cells near the outer region)
Cells located near the center near the outer region of the lobes rapidly secrete hydrogen ions into their cell walls, loosening them and allowing the walls to swell rapidly by osmosis
what causes the electrical charge that is propagated in the venus flytrap (cells in the inner portion)
The cells in the inner portion of the lobes and the midrib rapidly lose ions, leading to a loss of water by osmosis and collapse of these cells
examples include leaves closing at night, occur in circadian rhythms
sleep movements
24-hour cycles
circadian rhythms
circadian rhythms can be observed because at night the leaves fold upward into a shape resembling hands at prayer
prayer plant
plant that opens its flowers in the early part of the day and closes them at night
morning glory
morning glory
Ipomea leptophylla
in most plants, this is open in the morning and close at night
stomata
to qualify as circadian rhythm the activity must:
occur every 24 hours
take place in the absence of external stimuli (such as dim light)
be able to reset if external cues are provided
the internal mechanism by which a circadian rhythm is maintained in the absence of appropriate environmental stimuli
biological clock
Are synchronized by external stimuli to 24-hour rhythm
biological clock
the length of daylight compared to length of darkness, sets the biological clock
photoperiod
Also indicates seasonal changes better than temperature changes
photoperiod
as little no to effect in the biological clock
temperature
work with Arabidopsis and other organisms suggest that biological clock involves the transcription of this
clock genes
one model proposes that the information-transfer system from DNA to RNA to enzyme to metabolite, with all of its feedback controls, is intrinsically what and could be the basis for biological clocks
cyclical
describe the information transfer system (DNA -> metabolite)
DNA -> RNA -> Enzyme -> Metabolite
control sleep movements, the opening and closing of stomata, the discharge of floral fragrances, and the metabolic activities associated with photosynthesis
genes
also influences seasonal cycles that depend on day/night lengths, including the regulation of flowering
biological clock
outwardly very similar in all species
circadian rhythms
not the same in all species
clock genes
many physiological changes in flowering plants are related to this in day length
seasonal change
example of physiological change in flowering plants related to seasonal changes
seed germination
breaking of bud dormancy
onset of senescence
a physiological response prompted by changes in the length of day or night in a 24-hour daily cycle
photoperiodism
in some plants, photoperiodism can influence what
flowering
flowers in the spring
violets
tulips
flowers in the fall
goldenrod and asters
requires the participation of a biological clock (can measure time), and activity of a plant photoreceptor (phytochrome)
photoperiodism
measure time
biological clock
Greek words for photoperiodism
photos and periodus
photos mean
light
periodus means
course
blue-green leaf pigment that is present in the cytoplasm of plant cells
phytochrome
Greek words for phytochrome
phyton chroma
phyton means
plant
chroma means
color
composed of two identical proteins
phytochrome
portion of the phytochrome where the light-sensitive region is located
larger portion
can be said to act like a light switch because, like a light switch, it can be in the down (inactive) position or in the up (active) position
phytochrome
prevalent in daylight that activates phytochrome, and it assumes its active conformation known as Pfr
red light
active conformation of phytochrome
Pfr
when it moves to the nucleus, it interacts with specific proteins, such as a transcription factor
Pfr
activates certain genes and inactivates others (phytochrome)
Pfr and transcription factor
active form of phytochrome is called this way because it absorbs far-red light.
Pfr
prevalent in the evening and it serves to change Pfr to Pr
far red light
inactive form of phytochrome
Pr
a conversion cycle that is known to control various growth functions in plants
Pr -> Pfr
promotes seed germination and inhibits shoot elongation
Pfr
indicates to some seeds that sunlight is present and conditions are favorable for seed germination
prescence of far red
Reason why some seeds are only partly covered with soil when planted
to expose and activate Pfr
plants inhibited by light, so they must be planted deeper
arabidopsis seeds
what happens to seedlings that grow in the dark characterized by the: shoots increasing in length and leaves remaining small
etiolate
only when this happen does the seedling grow normally
conversion of Pr to Pfr
Flowering plants can be divided into three groups on the basis of their flowering status:
short-day plants
long-day plants
day neutral plants
flower when the day length is shorter than a critical length
short day plants
example of short day plants
cocklebur
goldenrod
poinsettia
chrysanthemum
length is longer than a critical length
long day plants
long day plants
wheat
barley
rose
iris
clover
are not dependent on day length for flowering
day neutral plants
example of day neutral plants
tomato
cucumber
criterion for designating plants as short-day or long-day
critical number
has a critical length of 14 hours
spinach
scientists discovered that it will not flower if required long dark period is interrupted by a brief flash of white light
cocklebur
will flower if an overly long dark period is interrupted by brief flash of white light
long day plant
which length controls flowering
length of dark period
when night is longer than a critical length, this kind of plant flowers
short day plant
The plant does not flower when the night is shorter than the critical length
short day plant
Does not flower if the longer-than-critical-length is interrupted by flash of light
short day plant
When the night is shorter than critical length, clover flowers
long day plant
The plant does not flower when the night is longer than a critical length
long day plant
does flower when a slightly longer-than-critical-length night is interrupted by a flash of light
long day plant
irreversible changes in cell size and plant organs due to cell enlargement and division
growth
transition from embryonic stages up to its later stages in maturation.
development
development includes the following:
growth
morphogenesis
differentiation
kind of growth wherein an organism stops growing as it reach a certain size
determinate
a kind of growth wherein cell keeps on dividing indefinitely
indeterminate
refers from the activity of apical meristems in which cell division is followed by progressive cell enlargement, typically elongation
primary growth
involves two lateral meristems: the vascular cambium and the cork cambium
secondary growth
gives rise to secondary xylem and phloem
vascular cambium
produces the periderm, consisting of many cork cells
cork cambium
lateral meristem that gives rise to the secondary xylem and secondary phloem
vascular cambium
external factors that affect growth
sunlight
wind
gravity
water
responses to environmental stimuli
tropic
nastic
taxis
growth response oriented with regard to the stimulus
tropic
stereotyped nongrowth response that is not oriented with regard to the stimulus
nastic
– response in which a cell swims toward (positive ) or away (negative) a stimulus
taxis
example of tropic response
phototropism
gravitropism
thigmotropism
chemotropism
nastic responses
photonasty
thigmonasty
nyctinasty
thermonasty
organic chemicals produced in one part of the plant and then transported to other parts, where they initiate a respond
plant hormones
identify the hormone:
abscission suppression
apical dominance
cell elongation
root formation in cuttings
auxin
identify the hormone
-bud activation
- cell division
- fruit/embryo development
- prevents leaf senescence
cytokinin
-converts some juveniles into adult condition and vice versa
- release seed from dormancy
- stem elongation
- stimulates pollen tube growth
gibberellins
-initiation of dormancy
- resistance to stress condition
- stomatal closure
abscisic acid
-fruit ripening and abscission
- initiation of root hairs
- latex production
- formation of aerenchyma in submerged roots
ethylene
level of organization where plant responses that promote survival and reproductive success have evolved through natural selection
species level
level of organization where some part or the entire plant responds to a stimulus
organismal level
level of organization where receptors receive signals, transduction pathways transform them, and genes or metabolic pathways react to them
cellular level
use a reception-transduction-response pathway when they respond to a stimulus
flowering plants
involved in phototropism and gravitropism. When a plant is exposed to light, auxin moves laterally from the bright to the shad side of the stem
auxin-controlled cell elongation
causes stem elongation between nodes.
giberellin
After this hormone binds to a plasma membrane receptor, a DNA-binding protein activates a gene leading to the production of amylase
giberellin
an enzyme that speeds the breakdown of amylase
amylase
cause cell division, the effects of which are especially obvious when plant tissues are grown in culture
cytokinin
two plant growth inhibitors
ABA and ethylene
well known for causing stomata to close
ABA
known for fruits to ripen
ethylene
when flowering plants respond to stimuli this occurs
growth and/or movement
growth responses toward or away a unidirectional stimuli
tropism
not directional
nastic movements
due to this some parts respond to touch and some perform sleep movement
turgor pressure
believed to be controlled by a biological clock
circadian rhythms
pigment involved in photoperiodism, the ability of plants to sense the length of the day and night during a 24-hour period
phytochrome
phytochrome activation can lead to
seed germination
shoot elongation
flowering of plants
causes phytochrome to exist as Pfr
day light (red light)
phytochrome during the night can be reconverted to this by metabolic processes
Pr
flower only when the days are shorter than a critical length
short day plants
flower only when the days are longer than a critical length
long day plants
have defenses against predators and parasites
flowering plants
routinely produced that protects plants from herbivores, particularly insects
secondary metabolites
causes plants to produce systemin
wounding
travels about the plant and causes cells to produce proteinase inhibitors that destroy an insects digestive enzymes
systemin
plants have permanent relationships with them, will attack predators
ants
