Limiting factors of Photosynthesis

What are the 3 factors that affect photosynthesis?

1) Light intensity 2) CO2 concentration 3) Temperature

1 of 12

What is a limiting factor?

When one of the factors needed for photosynthesis is in a short supply, it reduces the rate of photosynthesis, becoming a limiting factor

2 of 12

How does light intensity affect the rate of photosynthesis?

Light is needed to provide energy for the LD reaction, the higher the light intensity, the more energy it provides & the more ATP + NADPH is produced. Only certain wavelengths of light are used, such as red and blue light, while green is reflected

3 of 12

How does carbon dioxide concentration affect the rate of photosynthesis?

CO2 is needed as a source of carobn for the LI reaction (Calvin cycle). Increasing CO2 levels (to 0.4%) increases the rate of carbon fixation in the Calvin cycle, and the rate of TP production. Increasing above 0.4% means the stomata start to close

4 of 12

How does temperature affect the rate of photosynthesis?

It affects the rate of enzyme-controlled reactions (e.g. ATP synthase & RuBisCO), if temp falls BELOW 10⁰C the enzymes become inactive and ABOVE 45⁰C they denature

5 of 12

What else happens in the plant when the temperature exceeds 45⁰C? (1)

Stomata close to avoid losing too much H2O so less CO2 enters. Thylakoid membranes may be damaged reducing rate of LD reaction by reducing no. of sites available for e- transfer.

6 of 12

What happens in the plant when the temperature exceeds 45⁰C? (2)

Membranes around chloroplast become damaged, causing enzymes in the Calvin cycle to enter the cell, reducing rate of LD stages. Chlorophyll could be damaged, reducing amount of pigments that can absorb light energy, reducing rate of the LD reaction

7 of 12

What does it mean when the line on a graph showing the affect of a limiting factor on photoysnthesis plateau's?

It's the saturation point where increasing that limiting factor will not make a difference to the rate of photosynthesis because something else has become the limiting factor.

8 of 12

How can water stress affect photosynthesis?

When plants don't have enough water, their stomata close to preserve the water they do have, which means less CO2 can enter the leaf to initiate the Calvin cycle and therefore slowing photosynthesis

9 of 12

How does light intensity affect the levels of GP, RuBP and TP?

In low light intensities, the products of the LD stage (NADPH & ATP) will be in short supply, so the conversion of GP to TP and RuBP is slow. The level of GP will rise and levels of TP & RuBP will fall.

10 of 12

How does temperature affect the levels of GP, RuBP and TP?

At low temperatures all the reactions will be slower as enzymes work more slowly meaning the levels of RuBP, GP & TP fall. These are all affected in the same way at high temperatures as the enzymes will denature

11 of 12

How does CO2 concentration affect the levels of GP, RuBP and TP?

At low CO2 concentrations, conversion of RuBP to GP is slow (less CO2 to combine to RuBP to make GP). The level of RuBP will rise and levels of GP & TP will fall

12 of 12

Get Revising

Limiting factors of Photosynthesis

Other cards in this set

Card 2

Front

Back

Card 3

Front

Back

Card 4

Front

Back

Card 5

Front

Back

Comments

Similar Biology resources: