Limiting Factors In Photosynthesis

Question 1

What can photosynthesis be limited by?

Answer 1

-CO2 conc which is needed for Calvin cycle
-Light intensity which is needed in the LDR
-Temperature which affects enzymes like RUBISCO
-Amount of chlorophyll which needs electrons for ETC
-Water availability needed to replenish electrons at chlorophyll

Question 2

How can you monitor photosynthesis?

Answer 2

-Testing presence of starch using iodine
-Measuring volume of oxygen released
-Measuring volume of carbon dioxide used up

Question 3

What is light needed for?

Answer 3

To provide energy for the LDR

Question 4

Explain how light intensity affects rate of photosynthesis and graph

Answer 4

1) As light intensity increases, rate increases to a certain point, as light is the limiting factor due to being needed for photolysis
2) Beyond this, rate of photosynthesis remains constant as the light increases, due to something else becoming the limiting factor
3) E.g. carbon dioxide may have become the limiting factor, which is needed in the Calvin cycle

Question 6

Explain how carbon dioxide concentration affects photosynthesis and graph

Answer 6

1) As carbon dioxide concentration increases, the rate of photosynthesis increases as carbon dioxide is the limiting factor, it’s needed for the Calvin cycle
2) But, this is only to a certain point, as beyond this rate remains constant even tho CO2 conc increases
3) Something else has become the limiting factor e.g. light for photolysis

Question 7

Explain temperature as a limiting factor with this graph

Answer 7

A =
as temp inc, rate Inc, therefor temp is the limiting factor
-This occurs due to an Inc in Ke of enzymes e.g. RUBISCO/ATP synthase/dehydrogenase
B =
-This is the optimum temp so another factor is limiting e.g. light for photolysis
C =
-As temp inc, rate dec as enzymes of LDR/LIR have denatured

Question 8

Other than enzymes denaturing, how can a high temp affect photosynthesis?

Answer 8

-At high temp stomata close to avoid losing too much water
-This causes photosynthesis to slow down because less carbon dioxide enters the leaf when the stomata are closed

Question 9

What will happen if carbon dioxide is increased a bit too much?

Answer 9

The stomata start to close

Question 10

How is plant growth increased in glasshouses?

Answer 10

-CO2 is added to the air e.g. by burning fuels making CO2 in a generator
-Ligjt enters through glass
-Lamps give artificial light at night
-Glasshouses trap heat energy from sun, warming the air
-Heaters and cooling systems used to make optimum temp