Question

Study the graph which shows results of three different experiments $P,Q$ and $R$.
Concentrate on graphs $P$ and $Q$ and answer the following questions?
What is the different between the curves?

• A. The temperature has increased at $P$
• B. The rate of photosynthesis increased faster in $Q$ and in $P$
• C. The rate of photosynthesis lowered in $Q$ and $P$
• D. The temperature has lowered at $Q$

Answer 1

The correct option is A The temperature has increased at $P$

Although the light-dependent reactions of photosynthesis are not affected by changes in temperature, the light-independent reactions of photosynthesis are dependent on temperature. They are reactions catalysed by enzymes. As the enzyme approach their optimum temperatures the overall rate increases.It approximately doubles for every 10 degrees rise in temperature. Above The optimum temperature the rate begins to decrease, as enzymes are denatured until it stops.

In the given graph the rate of photosynthesis has become constant at a particular intensity of light. But in graph P the rate becomes constant at lower intensity suggesting an increase in temperature as a limiting factor for photosynthesis.