20. Signals from Sunlight Flashcards
photomorphogenesis
effect of light on plant development and growth
photoreceptors
detect and interpret light signals, initiate signal transduction pathways which ultimately trigger developmental responses
3 types of photoreceptors
phototropins
cryptochromes
phytochromes
which photoreceptors respond to blue light?
phototropins and cryptochromes
which photoreceptors respond to red light?
phytochromes
which photoreceptors would be most likely to detect light in the 400-500 nm wavelength range?
cryptochromes and phototropins
which photoreceptors would be most likely to detect light in the 650-720 nm wavelength range?
phytochromes
phytochromes are mostly used for:
photoperiodism
photoperiodism
the timing of plant processes in relation to the year
cryptochromes are primarily used for:
plant developement and photomorphogenesis, de-etiolation
phototropins are primarily used for:
phototropism and chloroplast relocation
in the stem, phototropins will be more active on the ___ side
sunny
in a stem, phototropins will be less active on the ___ side
shady
more active phototropins on the ___ side of the stem cause concentration of ____ on the shady side, leading to ____ of cells. This is called ___
sunny ; auxin ; elongation ; positive phototropism
etiolation
stems kept in the dark will grow long in search of light and lack chlorophyll
once it is exposed to light it will focus on leaf development
bending towards the light is is a ___ light response
blue
high light activates phototrpins to ___ stomata
close
which photoreceptor is most important for stomatal operature?
phototropins
which photoreceptor is most important for chloroplast relocation?
phototropins
which photoreceptor is most important for photoperiodism?
phytochromes
which photoreceptor is most important for de-etiolation?
cryptochrome
what is the most reliable trigger for photoreceptors?
length of day
short day and long day plants are actually sensing night or day length?
night length
why is night length important for plants?
during nighttime, Pfr –> Pr
it is the amount of Pfr that induces/inhibits flowering in plants, depending on whether they are SD/LN or LD/SN
what light is between 620 - 750 nm wavelength?
red
what light is between 700-780 nm wavelength?
far red
two forms of phytochrome are:
Pr (red light sensitive) and Pfr (far red sensitive)
light activates P__ to convert to P __
Pr –> Pfr
during nighttime, P__ converts/decays to P__
Pfr –> Pr
short nights/long day plants flower if P_ is __
Pfr is high
less has decayed to Pr overnight
long nights/short day plants flower if P_ is __
Pfr is low
more has decayed to Pr overnight
in short night plants, Pfr __ flowering
in long night plants, Pfr __ flowering
induces
inhibits
ratio of R:FR light indicates to plants:
orientation
under a canopy, there is less ___ light
green/blue/red
under a canopy, there is proportionally high __ light
far red
high far red : red light indicates to a plant that it is:
under a canopy
or has many neighbors that the FR is reflecting off of
high far red tells plants to _____ and inhibits _____
grow taller ; seed germination
phyochrome is a chromoprotein:
it has a pigment and a protein
far red - enriched light stimulates plants to:
increased stem elongation
far red light ___ seed germination
inhibits
inhibition of seed germination from ___ light can be reversed by ___ light
far red ; red
