How do you measure the rate of photosynthesis without immersing it in water and counting the bubbles?
Kindly clarify your statement as immersing the pot into water deals with a method of watering bonsai and is pretty unrelated to the rate of photosynthesis. When no more bubbles appear then you know that all the air bubbles existing in your soil media has been replaced by water molecules. In fact dunking is the only way to ensure the media has reached a 100% saturation, whereas the other methods recommended cannot guarantee this feature. You can measure photosynthesis in a number of ways: (1) Measuring the gases exchange in a closed chamber using CO2 sensitive instruments. (2) You may use a spectrophotometer to measure the rate of change of blue DPIP compounds which turn colorless when they absorb light electrons. (3) A hand held light sensitive measuring machine known as the EARS-PPM which can measure the amount of absorption of light of certain wavelengths in reflected light from leaf surfaces. (4) Measuring photosynthesis through chlorophyll fluorescence (5) Measuring the byproduct of photsynthesis O2 using an ultra sensitive O2 counting instrument. (6) Measuring the number of air bubles released during photosynthesis (a Canadian introduction which has been considered somewhat rudimentory by comparison) (7) A measuring instrument (known as the LI-COR developed by the New Mexico State University) that measures the quantity of CO2 injected into an air stream to replace the absorbed CO2 (used for photosynthesis) to maintain the equilibrium found in natural (incoming) air in the atmosphere. (8)and a hosts of other lesser accepted methods of measurements. Hope the above examples prove satisfactory to you.
