Chapter 39: Plant responses to internal and external signals Flashcards
Etiolation
Plants who are still underground will grow without sprouting leaves, only growing its roots until it finds sunlight
De-etiolation
After a plant finds sunlight it will quickly grow leaves to be able to gather the sunlight and photosynthesize
Hormone
An organic compound which allows the plant to react to its environment
Plant growth factor (or plant growth regulator)
Regulates plant growth to ensure it is growing at the right pace
Tropism
Growing towards or away from something, typically towards light
What are the three stages of signal processing?
Reception: Internal or external signals are picked up by the receptors, which send a signal to the second messenger
Transduction: the second messengers receive the signal and amplifies it to whatever part of the plant which reacts to the signal
Response: the plant responds to this stimuli by releasing hormones
What is a second messenger? What is its major role?
They are what is responsible for the transduction step, they amplify the signal and transfer it to the next step in the process
What are the two main mechanisms by which a signaling pathway can enhance an enzymatic step in a biochemical pathway?
Transcription regulation: Increases or decreases the production of a gene’s protein
Post-translational modifications: Activates specific proteins in signal response
What causes a coleoptile to bend toward light?
Auxin
Describe the experiments that led to the discovery of auxin.
Darwin-Darwin experiments: Led us to understand that something at the top of the plant causes the plant to grow towards some stimuli, cut off or covered certain parts of a coleoptile to see what part of the plant made it grow in the direction of light
Boyson-Jenson experiments: taught us that what is causing the growth is some type of molecule, since it can pass through gelatin but not mica
F.W. Went experiments: Gave us knowledge that the specific molecule is Auxin, did this by using a specific material that stored the hormone in it, when he put this material with auxin inside it it only had an effect on the part of the plant it touched, meaning that auxin is what was causing the elongation
What is the mechanism(s) involved in auxin’s stimulation of cell elongation in developing shoots?
Auxin loosens cell walls so that the cell can grow bigger, while also stimulating the cell to grow more cytoplasm and cell walls
What are cytokinin’s? What do they do?
They are a certain hormone which do nothing by themselves, however when introduced to some other chemical they can either cause cell division (when introduced to auxin) or cause apical dominance (when auxin and strigolactones are present)
What are the most important functions of gibberellins? How are they used commercially?
Stimulate growth in fruits and leaves, can be used commercially to make larger fruits by spraying them with gibberellins while they are still developing
What are the major functions of the brassinosteroids?
Causes elongation and division in the stem, and hold the plant from dropping leaves too early during fall
What is the role of abscisic acid in seed dormancy? Drought tolerance?
It causes seed dormancy, and slows down cell division, helps with drought tolerance
