<em>If the intensity and duration of exposure to light are increased for a duckweed plant, the rate of photosynthesis would increase and this would lead to an increase in the amount of oxygen produced.</em>
From the equation of photosynthesis:
the more the rate of photosynthesis, the more the amount of oxygen produced. Also, an increase in the intensity of light generally increases the rate of photosynthesis (and oxygen production) provided that other reactants can catch up. The rate of photosynthesis would become limited by the reactant that is available in the lowest quantity.
The central vacuole is the plant cell structure that stores large amounts of chemicals - including salts, minerals, proteins, and water - for the cell and helps the cell maintain its shape.