In photosynthesis, carbon dioxide, light energy, and water from the soil is used to create the plant's food, usually glucose. The waste product released is oxygen. I guess put oxygen for both boxes point out from the leaves.
The three boxes on the left are: light energy, CO2 (carbon dioxide) and H2O (water). On the right, one of the boxes would be O2 (oxygen) and the other glucose (sugar) since the making of sugar is the main purpose of photosynthesis.
