Plant Hormones and Tropisms Flashcards
track the sun as it moves through the sky
buttercups
example of light responses
sun tracking
help flowering plants respond to stimuli in a coordinated manner
hormones
season where seeds germinate, and growth begins if the soil is warm enough to contain liquid water
spring
season when temperatures drop, shoot- and root-apical growth ceases
fall
instrumental in detecting the photoperiod and bringing about genetic changes
phytochrome
plant defenses include: (3)
physical barrier
chemical toxins
mutualistic animals
can be associated with specific responses, some responses are probably influenced by the interaction of more than one hormone
plant hormones
bring about a response to both light and gravity and are involved in many other growth responses as well
auxins
effects include stem elongation between nodes, and this leads to several commercial uses of this hormone
gibberelins
causes cell division, and in tissue culture, to auxins affects differentiation and development
cytokinin
help regulate the closing of stomata
abscisic acid
causes fruits to ripen
ethylene
growth responses in plants toward or away from unidirectional stimuli, such as light and gravity
tropism
plants sometimes exhibit theses (e.g. closing of stomata), that recur approximately every 24 hours
circadian rhythm
length of daylight controls plant responses, involves the pigment phytochrome
photoperiod
defense mechanisms of plant
barriers to entry
chemical toxins
systemic mechanisms
relationship with animals
adaptive for organisms to respond to this because it leads to longevity and ultimately to the survival of the species
stimuli
perceive and react to a variety of environmental stimuli
flowering plants
example of stimuli
light
gravity
carbon dioxide levels
pathogen infection
drought
touch
short term responses of plants
opening and closing of stomata
long term responses of plants
downward growth of the root and upward root of the stem
utilize signal transduction when responding to stimuli
plant cells
proteins activated by a specific signal, can be located in the plasma membrane, the cytoplasm, the nucleus, or even the endoplasmic reticulum
receptors
Responds to light that has a pigment component
receptors
has a region that is sensitive to red light
phytochrome
has a region that Is sensitive to blue light
phototropin
series of relay proteins or enzymes that amplify and transform the signal to one understood by the machinery of the cell
transduction pathway
in some instances, this may immediately communicate with the transduction pathway
stimulated receptor
in other instances, this second messenger initiates the response
Ca2-
Analogy: a mother at work who wants a sitter to fix lunch for her children
which is the mother
stimulus
Analogy: a mother at work who wants a sitter to fix lunch for her children
which is the home
receptor of the cell
Analogy: a mother at work who wants a sitter to fix lunch for her children
which is the sitter
second messenger
Analogy: a mother at work who wants a sitter to fix lunch for her children
what is the lunch (activated)
transduction pathway
occurs as a result of the transduction pathway, result is either transcription of particular genes or end product of an activated methabolic pathway
cellular response
what happens to the gene once cellular response happens after the transduction pathway is activated
transcription
brings about the observed macroscopic response, such as stomata closing or a stem that turns toward the light
cellular response
between cells is required for macroscopic response to become evident, and is often dependent on plant hormones
coordination
greek word for hormone
hormao
meaning of hormao
to instigate
produced in very low concentrations and active in another part of organism
chemical signals
such as auxin, are synthesized or stored in one part of the plant, but they travel within phloem or from cell to cell response to the appropriate stimulus
hormones
are produced in shoot apical meristem and are found in young leaves and in flower and fruits
auxins
means promoting growth
auxinos
most common naturally occurring auxin
Indoleactic acid (IAA)
responsible for apical dominance, which occurs when the terminal bud produces new growth instead of axillary buds
auxin
Causes the growth of roots and fruits and prevents the loss of leaves and fruit
auxin
molecule is the plasma membrane, cytoplasm, or nucleus that receives the signal and becomes activated
receptor
a series of relay proteins that amplify and convert the original signal into one tht affects cellular machinery
transuction pathway
most often a change in gene expression or a cellular process affects plant growth and development
response
can be sprayed with auxin to keep mature fruit from falling to the ground
trees
used today in a number of applications such as Sprayed in plants such as tomatoes to induce the development of fruit without pollination
synthetic auxins
synthetic auxins that have been used as herbicides to control broadleaf weeds such as dandelions and other plants
2,4-D and 2,4,5-T
was banned in 1979 because of its detrimental effects on human and animal life
2,4,5-T
used in the Vietnam, a mixture of 2,4-D and 2,4,5-T
defoliant agent orange
when perceived by a flowering plant, the auxin moves to the lower surface of roots and stems
gravity
protective sheath for the young leaves of the seedlings
coleoptile
in 1881, together with his son has found phototropism will not occur if the tip of the seedling is cut off or covered by a black cap
charles darwin
in 1926, cut off the tips of coleoptiles and placed them on agar (a gelatin-like material), then he placed an agar block to one side of a tipless coleoptile and found that the shoot would curve away from that side
Frits W. Went
percentage of sunlight
52 - infrared
44 - visible light
4 - ultraviolet light
Greek word that the word auxin is named after, means promoting growth
auximos
When stem is exposed to unidirectional light, auxin moves what side, where it enters the nucleus and attaches to a receptor
shady side
leads to this activation and the resulting acidic conditions loosen the cell wall because hydrogen bonds are broken and cellulose fibrils are weakened by enzymatic action
proton pump (H+)
what weakens the cellulose fibrils
enzymatic action
result of the auxin moving to the shadier side
elongation of the stem
include gibberellic acid, GA3
70 Gibberelins
latin word for Gibberellins
gibbus
meaning of gibbus
bent
are applied externally to plants
gibberelins
most obvious effect of gibberellins
stem elongation
were discovered in 1926, the same year that Went performed on classic experiments in Auxin
gibberelins
Japanese scientist that was investigating a fungal disease of rice plants called “foolish seedling disease”
ewiti kurosawa
Kurosawa observed that plants elongated too quickly, causing the stem to weaken and the plant to collapse
the fungus infecting the plant produces an excess of what chemical
gibberelin
fungus where Gibberrellins was named after
gibberella fujikuroi
isolated from a flowering plant rather than from a fungus
gibberelic acid
source of gibberellin in flowering plants
young leaves, roots, embryos, seeds, and fruits
commercial use of gibberellins
-induce the growth of plants and increase size of flowers
-used to produce larger seedless grapes
-Caused an increase in the space between the grapes, allowing them to grow larger
-Hasten the development of flower bud
is a period of time when plant growth is suspended, this can be broken by gibberellins
dormancy
When gibberellins break the dormancy of this plant, a large, starchy endosperm is broken down into sugars to provide energy for growth
barley seeds
makes its appearance when gibberellins break the dormancy of seeds
amylase
where gibberellins are involved that lead to the production of amylase
transduction pathway
Greek word where cytokinin is derived from
kytos and kineo
greek word kytos for cytokinin means
cells
greek word kineo for cytokinin means
move
are derivatives of adenine one of the purine bases in DNA and RNA
cytokinin
cytokinin that is naturally occurring that was not isolated until 1967, was named after the kernels of maize (zea)
zeatin
was discovered as a result of attempts to grow plant tissue and organs in culture vessels in 1940s
cytokinin
what occurred when coconut milk (a liquid endosperm) and yeast extract are added to the culture medium
cell division
effective components that promote cell division, have been isolated from various seed plants, where they occur in the actively dividing tissues of roots and also in seeds and fruits
cytokinin
used to prolong the life of flower cuttings as well as vegetables in storage
cytokinin
synthetic cytokinins include
kinetin
benzyl adenine
benzylaminopurine
now common practice where the ratio of auxin to cytokinin and the acidity of the culture medium determine whether the plant tissue forms and undifferentiated mass
plant tissue culturing
undifferentiated mass that is formed
callus
Plant hormone rarely acts alone, instead it is a what
relative concentrations of hormones and their interactions that produce an effect
chemical fragments released from the cell wall, are also effective in directing differentiation
oligosaccharins
hypothesized that these are part of a reception-transduction-response pathway, which leads to the activation of enzymes that release the fragments from the cell wall
auxin and cytokinin
aging process, such as when a leaf loses its natural color
senescence
during senescence what happens to the large molecules within the leaf
broken down and transported to other parts of the plant
Does not always affect the entire plant at once, as some plants grow taller and naturally lose their lower leaves
senescence
Application of what can prevent the senescence of leaves
cytokinin
begin to grow, despite apical dominance, when cytokinin is applied to them
axillary buds
produced by any “green tissue” (that contains chloroplasts)
abscisic acid
Produced in monocot endosperm and roots
abscisic acid
Also produced in monocot endosperm and roots, where it is derived from carotenoid pigments
abscisic acid
abscisic acid is sometimes called what
stress hormone
initiates and maintains seed and bud dormancy and brings about the closure of stomata
abscisic acid
believed that ABA functioned in this, the dropping of leaves, fruits, and flowers from a plant
abcission
what hormone seems to bring about abscission
ethylene
period of low metabolic activity and arrested growth
dormancy
Occurs when a plant organ readies itself for adverse conditions by ceasing to grow (even though conditions at the time may be favorable for growth)
dormancy
believed that it moves from leaves to vegetative buds in the fall, and thereafter these buds are converted to winter buds
abscisic acid
covered by thick, hardened scales
winter bud
reduction and increase of what hormones are believed to break seed and bud dormancy
reduction of abscisic acid
increase in gibberelins
brings about the closing of stomata when a plant is under water stress
abscisic acid
induces rapid depolymerization of actin filaments and formation of a new type of actin that is randomly oriented throughout the cell
ABA
change in this may also be part of transduction pathways involved in stomata closure
actin organization
is a gas formed from the amino acid methionine, involved in abscission and the ripening of fruits
ethylene
amino acid where ethylene is formed
methionine
stimulates certain enzymes, such as cellulase, which helps cause leaf, fruit, or flower drop
ethylene
weakens cell walls, ethylene stimulates the production of this
cellulase
promotes the activity of enzymes that produce the flavor and smell of ripened fruits
cellulase
Breaks down chlorophyll, inducing the color changes associated with fruit ripening
cellulase
moves freely through a plant by diffusion, and because it is a gas, also moves freely through the air
ethylene
Can be released at the site of a plant wound due to physical damage or infection
ethylene
Used in agriculture is extensive, is used to hasten the ripening of green fruits such as melons and honeydews
ethylene
Applied to citrus fruits to attain pleasing colors before marketing
ethylene
ripen on the vine because the plants produce ethylene but it can be genetically modified to not produce ethylene
\
tomato
Facilitates shipping because green tomatoes are not subject to as much damage
genetically modified tomato
involved in axillary bud inhibition
ethylene
transported down from the apical meristem of the stem, stimulates the production of ethylene, which suppresses stem and root elongation
auxin
suppresses stem and root elongation
auxin
growth toward or away from a unidirectional stimulus
tropism
Greek word for Tropism
tropos
tropos means
turning
means that the stimulus is coming from only one direction instead of multiple directions
unidirectional
growth toward a stimulus
positive tropism
growth away from a stimulus
negative tropism
tropisms are due to this, one side of an organ elongates faster than the other, and the result is curving toward or away from the stimulus
differential growth
best known tropisms in plants
gravitropism
phototropism
thigmotropism
movement in response to gravity
gravitropism
movement in response to a light stimulus
phototropism
movement in response to touch
thigmotropism
other tropism other than light, gravity, and touch
chemotropism (chemicals)
traumatropism (trauma)
skototropism (darkness)
aerotropism (oxygen)
movement in response to chemicals
chemotropism
movement in response to trauma
traumatropism
movement in response to darkness
skototropism
movement in response to oxygen
aerotropism
first step towards a response
reception of stimulus
next step after reception of stimulus, meaning that the stimulus has been changed into a form that is meaningful to the organism
transduction
after the transduction, the organism will then show this
response
Latin word for Gravitropism
gravis
gravis means
heavy
along with his son, were the first to say that roots, in contrast to stems, show positive gravitropism
charles darwin
sensors in root caps which are starch grains located within amyloplasts, a type of plastid
statoliths
due to gravity, they settle to a lower part of the cell where they come in contact with cytoskeletal elements
amyloplast
elongates so that the root curves downward
upper surface of the root
elongates – so that the stem curves upwards
lower surface of the stem
occurs because the cells on the shady side of the stem elongate due to the presence of auxin
positive tropism
a plant curving away from light
negative tropism
depending on the species examined, are either insensitive to light or exhibit negative phototropism
roots
mutant plant that is studied to prove that phototropism occurs because plants respond to blue light
arabidopsis
when this is absorbed, the pigment portion of the photoreceptor, phototropin (phot) undergoes a conformation change
blue light
when blue light is absorbed, what happens to the phosphate group from ATP
transfer to a protein portion of the photoreceptor
