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External Factors Affecting Photosynthesis - Coggle Diagram
External Factors Affecting
Photosynthesis
Light Intensity
graph
A -
light is limiting factor
= as light increases, rate of PS increases
B - another factor also influencing + limiting rate PS
C -
light no longer limiting
= increase in light causes no further increase in PS
not normally
limiting
some plants adapted to grow
in shade (leaves extra chloroplasts)
deep below water surface
when NO LIGHT IS AVAILABLE
(in complete darkness)
ribulose biphosphate
and
glycerate phosphate
GP not converted to TP
∴ GP accumulates
GP conc INCREASES
any RuBP molecues present in stroma
fix CO2
form GP
but no more RuBP made from TP
RuBP conc DECREASES
conc of each molecule levels off as cycle grinds to a halt
graph
when light removed
light dependent steps of PS stop
∴ ATP and NADH + H+ no longer made
not available for light independent reactions
triose phosphate
and
glycerate phosphate
GP not converted to TP
GP accumulates
GP conc INCREASES
TP used up
converted to glucose/hexose sugar
TP conc DECREASES
graph
Limiting Factors
if a factor is limiting...
increase in its amount
increases rate of photoS
Non-Limiting Factors
if factor is non-limiting...
increase in its amount
will NOT increase rate of photoS
if limiting factor left unchanged
When chemical process is affected
by more than 1 factor
rate is limited
by factor nearest to its minimum value
Carbon Dioxide
main limiting factor of PS
(under normal conditions)
conc. in air is 0.03%-0.04%
graph
essential to PS
used in light independent reactions
supplies C atoms
to produce carbohydrates
when NO CO2 AVAILABLE
CO2 cannot be fixed
cannot combine with RuBP
∴ no more GP formed
GP molecules already present converted to TP
GP conc DECREASES
RuBP builds up as not being converted to GP
RuBP conc INCREASES
conc of each molecule levels off as cycle grinds to a halt
graph
Temperature
only is limiting
when
light intensity + CO2 conc are not
influence of temp -
increase in temperature
enzyme catalysed reactions
(of light dependent stage)
occur at FASTER RATE
at higher temps
enzymes become denatured
∴ rate PS reduced
plants (eg cacti + succulents)
adapted to live in hot + dry environments
enzymes
control all biochemical reactions
are temperature sensitive
Water
water involved many cell reactions
so effect on PS
difficult to measure
experiments show:
lack of water = loss of yield
due to
when plants are 'water stressed'
they close stomata to conserve water
ALSO
plant will wilt
and leaves no longer collect solar radiation