The first event in photosynthesis is

Explanation

1) There are two major phases found in photosynthesis. They are light reaction and dark reaction.
2) Light reaction : The light reaction takes place in chlorophyll containing thylakoids called grana of chloroplasts .
3) The chlorophyll on exposure to light energy becomes activated by absorbing photons.
4) The energy is used in splitting the water molecule into its two component ions.
`H_2O to H^(+)+OH^(-)`
This is known as photolysis of water.
5) `OH^(-)` ions through a series of steps produce water and oxygen. 6) ATP and NADPH are formed at the end of the light reaction are called assimilatory powers.
7) Dark reaction : Dark reactions do not depend on light. These reactions occur in stroma of chloroplast.
8) `H^(+)` ions produced in photolysis are immediately picked up by special compound NADP to form NADPH.
9) In the dark phase , the hydrogen of the NADPH is used to combine it with `CO_2`. by utilising ATP energy and to ultimately produce glucose.
10) The synthesis of glucose occurs in number of steps using certain special intermediate compounds (mainly ribulose biphosphate) and enzymes.
11) Finally the glucose is converted to starch.