The rate of photosynthesis is independent of:

Assertion : The atmospheric concentration of $CO_2$ at which photosynthesis just compensates for respiration is referred to as $CO_2$ compensation point.
Reason : The $CO_2$ compensation point is reached when the amount of $CO_2$ uptake is less than that generated through respiration because the level of $CO_2$ in the atmosphere is more than that required for achieving $CO_2$ compensation point.

The excess amount of $CO_2$:

The law of limiting factors was proposed with particular reference to photosynthesis. Identify the scientist who proposed this law.

Look at leaves of the same plant on the shady side and compare them with the leaves on the sunny side. Or,compare the potted plants kept in the sunlight with those in the shade. Which of them has leaves that are darker green? Why?

$DCMU$ is a herbicide which kills the plant by