Factors affecting photosymnthesis

Question 1

Why is water never considered a limiting factor?

Answer 1

• it is needed
• but for water potential to have become low enough to limit the rate of photosynthesis the plant will have already closed its stomata and ceased photosynthesis
  
  • excepted plants able to tolerate drought condiitions

Question 2

How can limiting factors be investigated?

Answer 2

• data loggers

Question 3

What is the effect of reducing light intensity?

Answer 3

• reduce the rate of light-dependant stage of photosyntheiss
• this will reduce the quantity of ATP and reduced NADP reduced

Question 4

What effect will reducing the light intensity have on the products of the calvin cycle?

Answer 4

• ATP and reduced NADP needed to convert GP to TP
• conc of GP will increase and TP will decrease
• less TP to regenerate RuBP, the conc of RuBP will decrease
• reverse will happen when light intensity is increased

Question 5

What is the effect of reducing temperature?

Answer 5

• reactions are catalysed by enzyme
• at low temp
  
  • enzyme and substrate molc have lower KE
  • resulting in fewer successful collision
  • reduced rate of reaction
• results in lower conc of GP, TP and RuBP
• same effect will seen at high temps as enzymes will be irreversibly denatured

Question 6

WHat is the effect of carbon dioxide on the Calvin cycle?

Answer 6

• reducing will increase conc of RuBP as it is not fixed

Question 7

What is a limiting factor?

Answer 7

• factor that limits rate when less than optimal level

Question 8

Moderate temperature stress causes deactivation of RuBisCO and reduces stomatal aperture

what is the effect on photosynthesis?

Answer 8

• deactivation of RuBisCO
  
  • reduce carbon fixation / LIR
• the light dependent reaction will reduce when the supply of NADP is reduced
• reduction in stomatal aperture will reduce carbon dioxide available for fixation

Question 9

What are the ways the ultrastructure of the chlroplast can be altered??

Answer 9

• damage to chlorophyll / reduction in pigment which will reduce the light dependent stage
• damage to membranes in chloroplast / reduction in sites for light capture which will reduce the light dependent stage
• damage to membranes in chloroplast / reduction in reaction sites for electron transfer which will reduce, photophosphorylation / ATP production in the light dependent stage
• damage to membrane around chloroplast / release of enzymes which will reduce, light independent stage / Calvin cycle