(a) 1.During photosynthesis, plants trap solar energy and by utilising simple inorganic substances like CO2 and H2O, they prepare complex organic substances like carbohydrates.
These carbohydrates are utilised for providing energy for most living organisms including human beings.
It is the only process which adds O2 to the atmosphere and makes our living possible.
(b) 1. Dark reaction of photosynthesis does not require light energy.
The term dark reaction does not mean that they occur when it is dark or at night.
It only means that the reactions are not dependent on light as in light reaction.
(c) 1. To get better results from related experiment, it is necessary to destarch a plant before performing any experiment on photosynthesis.
The plant which is kept in the dark place for few days for the removal of starch from the leaves, is called a destarched plant.
It is to precisely to estimate the amount of starch produced after experiment.
(d) 1. During day time, plants carryout photosynthesis actively.
During this time O2 given out as a by-product is taken up by plants for respiration.
Not only this, CO2 produced during respiration will be used in photosynthesis.
Thus, both photosynthesis and respiration are inter related, it is not possible to demonstrate respiration during day time.
