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