Signal Transduction Pathways
Define etiolation.
Etiolation: morphological adaptations for growing in darkness
Define hormone.
Hormone: a signaling molecule produced in one part of the body and transported to other parts
How do cytokinins slow plant aging?
cytokinins inhibit protein breakdown,
stimulate RNA and protein synthesis, and mobilize nutrients from tissues surrounding plant organs
What occurs during transcriptional regulation?
transcription factors bind directly to specific regions of DNA in order to control gene expression
What are the effects of cytokinins?
they increase cell division and differentiation, inhibit apical dominance, and delay senescence
A seed that has been dormant for years germinates after several days of heavy rainfall. Which hormone was added or removed?
ABA was removed due to the heavy rain, triggering germination
What are four factors that plants respond to?
Answers may include: light, heat or cold stress, internal chemical signals, touch by wind or objects, drought or flooding, time, gravity, wounding by herbivores, and infection by pathogens
What are the steps of ethylene's triple response?
1. slowing of stem elongation
2. stem thickening
3. horizontal stem growth
Why do monocots exhibit parallel leaf venation?
auxin directs a plant's leaf venation pattern
What types of enzymes does de-etiolation activate?
1. those that function in photosynthesis directly
2. those that supply the chemical precursors for chlorophyll production
3. those that affect the levels of plant hormones that regulate growth
How does auxin cause cell elongation?
- the cell wall activates proton pumps
- auxin increases the activity of the proton pumps
- cell wall loosening enzymes cleave polysaccharides
- microfibrils loosen from their rigid state, allowing cell to elongate
While studying seed germination, you notice that the starch inside the seed has begun to breakdown. How does this occur?
the embryo releases gibberellins, which stimulate the production of α-amylase (enzyme that breaks down starch into smaller molecules)
Go through the stages of cell signaling.
Reception: hormone/stimulus binds to a protein receptor
Transduction: second messengers transfer and amplify from receptors to intracellular proteins
Response: cell changes its behavior (a specific response is incited)
What is the difference between ein mutants and ctr mutants?
ethylene-insensitive mutants don't undergo the triple response after exposure to ethylene
constitutive triple-response mutants always undergo the triple response (even in the absence of ethylene)
ethylene because it triggers fruit ripening