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Coordination + Control in Plants - Coggle Diagram
Coordination + Control
in Plants
Phytochrome
D: pigment
found in leaves
of flowering plants
sensitive to light
involved in timing of
flowering in plants
blue-green pigment
(reflects blue-green light)
ACT AS
PHOTORECEPTOR
role aided by...
ability to exist in 2 inter-convertible forms
P660
P730
P(660)/PR
absorbs
RED
light
w/ absorption peak of 660nm
when exposed to red light/white light
converted to PFR
RAPIDLY
daylight
contains far
much
more red light
∴ PFR predominates during day
light INTENSITY also important
higher LE
conversion PR to PFR quicker
P(730)/PFR
absorbs
FAR-RED
light
w/ absorption peak of 730nm
when in darkness
converted back to PR
SLOWLY
when exposed to far red light
converted to PR
RAPIDLY
*predominates during day
physiologically
active form
in LDPs = P730 needs accumulated
to cause flowering
in SDPs = too much P730
prevents flowering
Photoperiodism
most activity in
plants = SEASONAL
due to
photoperiod
(D: duration of light/day length)
D: response of living organisms to
change in day length
Long-Day Plants
examples
cabbage
petunia
D: flower only if day length
EXCEEDS
certain min length
short day
&
long night
during short day
white light converts
P660 to P730
rapidly
during long night
dark period long enough
P730 slowly converted to P660
∴ @ end of night -
LOW
level of P730
∴ NO FLOWERING
long day
&
short night
during long day
high conc of...
P660 converted to P730
during short night
dark period too short
for P730 be converted back to P660
∴ @ end of night -
HIGH
level of P730
∴ FLOWERING
flowering
STIMULATED
by
presence of P(730)
Short-Day Plants
examples
chrysanthemum
strawberry
D: only flower if days
SHORTER
than critical value
flowering
INHIBITED
by
presence of P(730)
short day &
long night
during short day
P660 converted rapidly to P730
during long night
dark period long enough
convert
ALL
P730 back to P660
∴ NO P730 left
∴ FLOWERING
long day
&
short night
during long day
P660 converted to P730
in high concentrations
during short night
dark period not long enough
for enough P730 to be converted to P660
@ end of night -
high
levels of P730
∴ NO FLOWERING
critical period of darkness must be
continuous
(uninterrupted)
why?
short flash of light
rapidly convert P660 to P730
Manipulating the
Photoperiod
WHY?
commercial plant growers
need flowering plants available
@ times of yr when sales high
eg Valentines/Christmas
HOW?
use lamps
to increase light duration
cause conversion P660 to P730
in LONG DAY
plants
flowering brought forward/delayed
manipulating photoperiod
using screens
to reduce light
period
using artificial lighting in glasshouses
short darkness
during day
period of darkness
interrupts light period
does not reduce P730 level enough
to inhibit flowering
in SHORT DAY
plants
flowering times adjusted
manipulating photoperiod
short flash of light during
long night
flash of light
rapidly convert P660 to P730
too short night after
to convert P730 back to P660
∴ @ end of night = high level of P730
∴ flowering inhibited
Plant Growth Substances
control many aspects
of plant growth
role
accelerate
inhibit
modify growth
tropisms
D: movements of part of plant in response to an external stimulus
Positive = growth towards
Negative = growth away from
stimulus = light
PHOTOTROPISM
in plants -
growth localised in specific zones
TIPS of roots + shoots =
APICAL MERISTEMS
AUXINS
produced
in tip
moves down stem
role
promote growth
by increased
cell elongation
(in zone of elongation)
CYTOKININS
produced
in meristematic tissue
(actively dividing)
in zone of division
role
promote growth
by increased
cell division
in
apical meristems
(zone of division)
GIBBERELLINS
produced
produced in leaves
role
promote growth
by
cell elongation
in
internodes