FACTORS AFFECTING THE RATE OF PHOTOSYNTHESIS

Factors affecting rate of photosynthesis

1. Dathan C S
Factors affecting rate of photosynthesis

2. The process of photosynthesis is affected by
two types of factors namely:
1.External factors
2.Internal factors
-

3. External factors
a. Sunlight
b. Temperature
c. Carbon dioxide
d. Water and
e. Minerals

4. The three main things affecting the
rate of photosynthesis are:
Light
Temperature
Carbon dioxide
These three factors are called LIMITING FACTORS.

5. •Law of limiting factors:
“The overall rate of the process will be
limited by the factor which is at the least
favorable value”

6. Light
The rate of photosynthesis increases when light
gets brighter

7. Effect of light

11. Light response curve-C3 and C4 plants

12. Light saturation point

13. Light compensation point
•Rate of photosynthesis is equal to rate of
respiration
•the light intensity at which the amount of carbon
dioxide released in respiration equals the amount
used in photosynthesis and the amount of
oxygen used in respiration equals the amount
released in photosynthesis, varying in different
species of plants and in response to changes in
temperature and other environmental factors

16. Temperature
The higher the temperature then typically the
greater the rate of photosynthesis

18. Carbon dioxide
An increase in the concentration of carbon dioxide
gives an increase in the rate of photosynthesis.

19. Ethanol plant, Ontario, Canada

22. Co2 compensation point
• The level at which the oxygen production rate
drops to zero is called the compensation point
for carbon dioxide.
•it represents the CO
2
concentration at which
CO
2
consumption in photosynthesis is balanced
by CO
2
production in photorespiration

23. CO
2
 Saturation Point
•The CO
2
 Saturation Point of Photosynthesis. At
this point increases in CO
2
concentration do not
cause increases in photosynthetic rate, so factors
other than the supply of CO
2
must be limiting the
photosynthetic process. These factors include:
• a) The supply of light to the leaf.
b) The amount, and turn-over rate, of
enzymes involved in the "dark reactions" of
photosynthesis.

24. Co2 compensation point-c3 and c4
plants

25. Global warming

26. Global warming and co2

27. Global warming-C3 and C4
•in bright sunlight and warm temperatures, C4 plants grow
faster than C3 ones. yield advantage of C4 plants in hot
weather
•C4 plants are better at scavenging carbon dioxide (the
source of carbon for sugars) from the air and waste much
less water
•whereas rising temperatures benefit C4, rising carbon-
dioxide levels do not. In fact, C3 plants get a greater boost
from high carbon dioxide levels than C4. Nearly 500
separate experiments confirm that if carbon-dioxide levels
roughly double from preindustrial levels, rice and wheat
yields will be on average 36% and 33% higher, while corn
yields will increase by only 24%.

28. •C4 has a larger share of the market in weeds.
battle against weeds should get easier as
carbon dioxide levels rise-because C3 crops
can accelerate their growth more than C4
weeds can.

29. Water
•Water stress leads to stomata closure, less
absorption of Co2 and less photosynthetic
rate
•No water logging: as it can reduce mineral
uptake by active transport which affect the
rate of process

30. Minerals
•All nutrients needed at optimum
concentrations
•Pottasium particularly important in stomatal
mechanisms so must be at desirable levels

31. Internal factors
•Chlorophyll
•Leaf anatomy
•Accumulation of end products
•Hormones
•Rubisco Performance
•Rate of Chloroplast Electron Transport
•Enzyme Activity of Calvin Cycle

32. Internal factors
•Capacity of Metabolite Transport Processes
and Carbon Utilization
•Stomatal characteristics etc..

33. Thnx all