National 45 Biology Section 4 Photosynthesis Limiting factors

National 4/5 Biology Section 4: Photosynthesis Limiting factors

What do we know so far? �Graffiti �On your piece of paper write down continuously everything you know about/related to photosynthesis �Now look at what everyone has written and try to think about whether any of it will affect how quickly photosynthesis takes place

What are limiting factors? �Limiting factors are any factor that could alter the rate of photosynthesis. �There are probably many but the main ones studied are temperature, light intensity and CO 2 concentration. �Why is this?

This is why �Light - Light will alter the rate of the first stage (photolysis) as it is light dependant. �Temperature will alter the second stage (carbon fixation) as it depends on enzymes for it to work. �CO 2 concentration CO 2 will alter the second stage as it is a raw material in that stage.

How is rate of photosynthesis measured? �Rate of photosynthesis measured by: production of oxygen over a set period of time uptake of CO 2 over a set period of time production of glucose over a set period of time

Limiting factor graphs �What is the limiting factor at point A? �Carbon dioxide concentration – as CO 2 concentration increases so does the rate of photosynthesis B A �What is limiting at point B? �Something else (temp or light intensity) Carbon dioxide concentration is no longer having an effect – rate of photosynthesis is remaining constant even though CO 2 concentration is still increasing

Little bit tricky!? �What is the limiting factor at point X? �Light intensity – as light intensity increases so does the rate of photosynthesis �What is the limiting factor at point Y? �Temperature – rate of photosynthesis is less at the lower temperature

The last one �In the graph carbon dioxide concentration is limiting at points A 1, A 2 and A 3 �What is limiting at point X? �Light intensity X

Experiment �BBC - Learning Zone Class Clips - Producton of oxygen in plants Biology Video �Discuss how variables were controlled and what variables he actually changed �What variables could you investigate in class? �Your teacher will show you how to set up two investigations using the plant cabomba