Explanation:
Leaf disks float normally,when the air spaces are replaced with water the overall density of the leaf disk increases and the disk sinks
The saturating solution should include a small amount of sodium bicarbonate
Bicarbonate ion serves as the carbon source for photosynthesis
As photosynthesis proceeds, oxygen accumulates in the air spaces of the spongy mesophyll, the leaf becomes buoyant and floats
While this is going on, the leaf is also carrying out cellular respiration; this respiration will consume the oxygen that has accumulated and possibly cause the plant disks to sink
The rate that the disks rise is an indirect measurement of the net rate of photosynthesis
