Photosynthesis - Limiting Factors WALT : Explain that Photosynthesis rate is affected by environmental factors Explain How to measure the rate of photosynthesis WILF – Graph of Results Questions answered

Limiting Factors Light Intensity Carbon dioxide Temperature Resources that affect the maximum rate of photosynthesis For your test you need to know 3: Light Intensity Carbon dioxide Temperature

Light Levels What happens to the rate of photosynthesis when you increase the light level at low temperatures increase the light level at high temperatures

1a) As you increase light intensity, the rate of Photosynthesis increases but levels off quickly at low temperatures 1b) At high temperatures the rate of photosynthesis continues to rise

1b) When you increase the light levels at low temperature the rate of photosynthesis increases exponentially until another limiting factor takes over

Carbon dioxide levels 2) What happens to the rate of photosynthesis when you increase the CO2 level?

Temperature At low temperatures photosynthesis enzymes stop working At high temperatures the photosynthesis enzymes are denatured (broken up) 3) What happens to the rate of photosynthesis when you increase the temperature that the plant is in?

3) As you increase the temperature, the rate of photosynthesis increases up to a point. Beyond this temperature the enzymes denature and photosynthesis quickly stops

Practical – Measuring Rate of Photosynthesis                                  

Graph the following results Graph the following results. You may use the same paper, but be aware of the axes Remember : What you change goes on the x axis, what you measure on the y axis

Increasing Light Intensity Number of bubbles produced 1.0 4 2.6 8 4.2 11 5.2 14 6.5 13 7.3 8.6 16 10.0 17

Increasing CO2 Concentration Concentration of CO2 Number of bubbles produced 2.0 16 2.3 18 2.9 20 3.8 26 4.5 27 5.2 6.0 6.7

What can we say about these results? Discuss with your neighbour Think of an ‘er, er’ rule we can make

The greater the light intensity the more bubbles are produced What happens to the number of bubbles produced when CO2 levels are increased?

The number of bubbles produced levels off This is because a limited amout of something else occurs (eg light or temperature)