How to measure the the rate of photosynthesis?

Question

How would you measure the rate of photosynthesis for a plant that is not in a liquid solution (without counting oxygen bubbles)?

Answer 1

The rate of a biochemical process can be measured by examinng the disappearance of reactants (carbon dioxide and water) or the appearance of products (oxygen or carbohydrates). Since life uses water as a solvent, measuring changes in water concentration is not practical...like measuring a change in sea level after peeing in the ocean). Thus, we have three possibilities:

1.) carbon dioxide disappearance
2.) oxygen production
3.) carbohydrate accumulation

Since you're talking about counting oxygen bubbles, I assume that you don't have any sophisticated manometers, infrared gas analyzers, etc. The simplest, albeit crude, measurement you could do is to measure changes in starch contents in leaves. This can be used by adding iodine to the leaves (usually boiled in alcohol to remove green pigment). Iodine turns black in the presence of starch.