Plants and Environment Flashcards
Lecture 12
What do plants sophisticated mechanisms do?
collect information about their environment and respond in ways that maximize fitness
what happens when a sensory cell receives a stimulus?
it transduces the signal via receptors and produces hormones that carry information to target cells elsewhere in the body
how do target cells respond to hormones?
via other receptors with changes in cell function
how does a single plant hormone affect the plant
affect many different target tissues or processes
how do several plant hormones affect the plant
can affect the same response: hormones don’t work independently
how and where are plant hormones transported
transported in xylem, phloem, by diffusion or cytoplasmic streaming
How do plants mainly respond to the environment
by changing growth and morphology
what is positive phototropism
growth of plant tip towards light
what is positive phototropism caused by
differential growth of cells on opposite sides of coleoptile
if a shoot has a permeable barrier, what can it do?
it can still bend
hypothesized hormone on agar block can be used to do what?
to bend the shoot either way depending on how the block is placed
what way does the shoot bend?
it bends away from the side with more hormone
what was the first plant hormone discovered
Auxin (the phototropic hormones)
photoreceptors allow plants to do what?
detect the presence direction, intensity, and wavelength of light
what colour light does a phototropic response occur with?
blue light (or full light)
why do phototropic responses only occur with blue light?
because it is mediated by the light receptor phototropin that is specifically sensitive to the blue part of the light spectrum
what lights are photosynthesis most effective with and why?
blue and red light because chlorophyll is most sensitive to these wavelengths
what are phototropins?
blue light photoreceptors
characteristics of phototropins
- proteins encoded by PHOT1/2 genes
- involved in phototropic response
- involved in light-dependent opening and closing of stomata
what are cryptochromes involved in?
the timing of flowering
phytochrome photoreceptors characteristics
- absorbs mainly red/far red light
- switches between two different confirmations
- involved in seed germination and shade avoidance
what does red light do?
drives photosynthesis
what does far-red light do?
indicates shade
first stage of signal transduction
increases number of proton pumps in plasma membrane
