During photosynthesis the following events occur:
(i) Absorption of light energy by the chlorophyll pigment.
(ii) Conversion of light energy into chemical energy.
(iii) Splitting of water molecules into hydrogen and oxygen.
(iv) Reduction of carbon dioxide into carbohydrates.
Not necessarily. For example, desert plants take up carbon dioxide at night and prepare an intermediate compound. This intermediate compound is acted upon by the energy absorbed during the day by the chlorophyll.
State the part played by each of the following in photosynthesis:
(a) Water (b)Chlorophyll (c) Stomata.
(a) Water: Water (H2O) undergo photosynthesis in light reaction.
H2O → 2H+ + O + 2e–
O + O → O2 ↑
As a result ATP and NADPH are formed which are used in formation of carbohydrates from CO2. 
Water also releases O2 which is given out during photosynthesis.
(b) Chlorophyll: It traps solar (light) energy and utilises it in fixing oxides of carbon (CO2) and hydrogen (H2O) as carbohydrates.
(c) Stomata: They help in exchange of gases. Carbon dioxide needed in photosynthesis is taken in through stomata. Oxygen produced in photosynthesis is given out through stomata.
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