The graph shows the outcomes of a classroom investigation into the factors influencing the rate of photosynthesis. The variable investigated was either light intensity or CO₂ concentration.

problem 1: Propose an appropriate plant for such an investigation.

problem 2: How was the rate of the photosynthesis measured?

problem 3: Name a factor which must be kept constant throughout this investigation.

problem 4: Describe how you would keep constant the factor referred to in (3).

problem 5: Why is it essential to keep that factor constant?

problem 6: What happens to the rate of photosynthesis at X when the investigation is:

a) Carried out at 25^oC?

b) Carried out at 35^oC?

Give a reason for each of the answer.