Plants Response To Internal And External Signals Flashcards
Exogenous signal
A signal coming from outside the body such as light
Endogenous signal
A chemical signal within the body
Can be hormones or neurotransmitters
What did Darwin notice with plants ( what was his experiment)
That they bend towards light
This led to the question of what pet was responsible in bending the plant towards the light. They thought the tip so the cut it off. To further support they put an opaque cap that covered light and the plant didn’t respond. To go even further they got a translucent cap and the plant did bend. Adding a collar to the middle of the plant didn’t prevent the bending either further supporting the tip of the plant causing the bend
Boysen jenson experiment
Used gelatin slaps because it’s not solid so molecules can diffuse through it. They tested if the tip senses the light and then sends a signal in the form of a molecule to the other part of the plant. They cut the tip off and put a slap of gelatin between stock and tip and put it back in place. Even though tip was removed the stem still bender towards the light further supporting the tip sensing the light for the bend. Solid mica slab was also used in the same way and no bending occurred so it is most likely molecular signal.
Signal transduction
Tone signal get converted in another signal. Light to plant that causes the plant to release a signal to bend
Agar cubes allowed for
The plant tip to be put on and left for a while so the molecule could be absorbed and then the agar cube was put on to the cut stem and the plant still bent without its tip.
What are chemical signals
Just molecules
They have no effect unless there is a specific receptor where a chemical signal can bind
How are chemical signal categorized
What are the ones in humans
How they work
Hormones
and neurotransmitters
Neurotransmitters
They work locally ( cell to cell) and release by Newton’s and work right next to that
Hormones
Work through the bloodstream to broadcast a signal.
What kinds of molecules are receptors
Proteins
Auxin (IAA)
First hormone discovered
(Indolasedic acid)
Growth hormone -stem elongation from low concentration only(
Promotes lateral and adventitious roots
Enhances apical dominance
Rudimentary releases and the receptor turns on a proton pump that pumps proton near cell wall make the fluid on the outside more acidic. Acidity promotes enzymes that clip parts of the cell way but only happens on the sides and not the ends so stretches for stem elongation
Does how much of a hormone matter to the effect
Yes certain concentration of the same hormone can do different or opposite things. Can do different things to the body possibly based on the receptor
Cytokinins
Plant hormone
Regulate cell division In Roots and shoots
Gibberelellins
Stimulates growth and fruit growth
Used to make grapes way bigger without molding by also growing the stems
Can cause booting in certain kinds of species and stem elongation
In seeds these chemical signal is release by the endosperm and reaches the aluerone cells that respond to the chemical and make amylase which break down glucose to break down starch in the embryo to feed the embryo
Brassinosteroids
Phytosterol.
At high concentrations they inhibit root growth and at low concentration they promote root growth
What are the major steroid hormones in humans
Sex hormones
Initial steroid that gets modified and turns into something else is cholesterol
What get slightly modified in animals regarding their steroids
Cholesterol is the base of all steroids
For plants what is the base of their steroids
Phytosterol
Abscisic Avis (ABA)
Named for the process of abscission which is the loss of leaves.
But doesn’t cause leaves to fail so misnomer
Inhibits growth
Stomata closure
Promote leaf senescence or aging
Ethylene
Responsible for the ripening of fruit
Bolting In plate is what
Very rapid growth
What tells seeds to germinate
A sufficient amount of water. Which is an exogenous signal
What is starch made out of
Glucose
Ethylene controlls the
Triple response
What are the triple responses
The root slows down its lengthening and get wider.
The root is shoot with start growing horizontally for a while and will
then grow down if a root if it can
These are cause by ethylene
Constitutive triple response
Always turned on gene
Turn a gene on when it shouldn’t always be on so can cause a root or shoot to think ethylene is there are will always undergo triple response
Abscission is caused by how many hormones
Two
Ethylene and Auxin
Abscission
Ethylene Auxin ratio causes it
Leaf produces auxin and stem produces ethylene
Petiole has a ratio
Leaf my produce less auxin and the and the same ethylene by the stem so the ratio gets bigger cause the leaf to gradually fall off
Photomorphogenesis
The bringing about a change in shape in response to light.
This is what happens in potatoes. If you put them in light they will sprout green leaves and stems but In dark they grow white stout stems because it thinks its growing through the ground in the dark
Blue light receptors
Responds to blue light
Phytochrome’s
Responds to red light or red light receptors
Can cause a seed to germinate but if far red light( light past red we can see) is shined onto a seed then the seed will not germinate. Only if you shine the red light again without the far red after will it germinate. The receptors act as light switches for germination
It is a protein, operates based on its shape or conformation. One shape that is for red light is called Pr and Pfr shape is for far red light
Shinning light on Pr will change its shape to Pfr and viceversa
Tropism ( phototropsim
Refers to a response to a signal so phototropism means response to light
Circadian rhythms
Built in clocks in rhythms that are not exactly a day per day clock. Organisms reset their clocks so they are exactly 24 hours
Plants use light to reset
Circanual rhythms
Animals have these sometime for mating seasons. Plants need these to know what time of year it is.
Phytocromes also reset these life through the presence of light and how long it light or dark
Angiosperms can be classified based on their flowers that move
Short day or long night plants Unless night is long enough the plant will produce a flower
Long day plants and short night plants
Won’t produce a flower unless night is short.
They can be fooled by a blast of light by either thinking there is 2 short night so will produce or not produce flowers based on what type of response they have
Gravitropism
A response to gravity
Roots that response to this are positive tropism
Positive and negative tropism
The response to that stimulus is towards that stimulus - positive
The response to the stimulus is away from it -negative
How do roots sense gravity
Statoliths - is a little gradual of densely packed starch that is there to make the statolith dense so it’s heavier than its surrounding. It falls to the bottom of the cell and wherever it lands tells the cell that is down. Can tell plant where to drop roots and shoots
Otoliths in humans
Little sand like particles in our ears that are responsible for telling our brain what position our head is in space.
Thigmatopism
Is the response to touch
Leaflets that fold up on a certain plant
Electrochemical signals used in organism are called
Used in neurons and muscle cells are called action potentials. Voltage signals because they vary ions which have charge
Very fast in animals but not as fast in plants
Drought is a
Environmental stressor. Plants deal with this by producing abscisic acid because they control the opening and closing of stomata
Saturated fatty acids don’t have any
Bends in them
Unsaturated fates have bend in them and can loosen up sell membrane allowing them to live in cold places
