Dear Jose Kallarackal,

Please, look at the following article:

Underwater Photosynthesis of Submerged Plants – Recent Advances and Methods

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3659369/

Chlorophyll fluorescence and OJIP could be one of the important and recent photosynthesis traits for plants grown under this situation

OJIP Chlorophyll Fluorescence (CF) can measure primary photosynthetic electron transport but it does not measure photosynthesis (PS). CF OJIP is a good guess but still an over-simplification. Moreover, several processes such as photorespiration, nitrogen metabolism and the Mehler reaction may interfere with electron transport phenomena related to primary photosynthetic events... You can use CF OJIP to study some aspects of PS but you must keep in mind that it is not a direct measure of PS.

PS is estimated by measuring Carbon fixation and Oxygen evolution measured with IRGA equipment. Unfortunately, not submersible techniques has been developed for measuring PS with IRGA equipment underwater...

CF measured with the PAM technique is the closest method to gas exchange IRGA for measuring Photosynthesis. Therefore, I will recommend the diving PAM machine for measuring underwater photosynthesis.

http://www.walz.com/products/chl_p700/diving-pam/features.html

One more thing: if you want to measure attached leaves in underwater submerged conditions, then you can use a diving-PAM but if you can take samples from the underwater flora and measure them out of water, then you can measure Photosynthesis with any IRGA gas analyzer equipment for measuring CO2 exchange. Complementary, you could measure Chl a fluorescence induction with Pulse Amplitude Modulation technique or Fast OJIP fluorescence curves. I am curious about measuring fluorescence with a P700+fluorometer (e.g. with the so called M-PEA fluorometer) to measure absorption at (about) 820 nm on seaweeds from deep underwater as their pigments usually do not absorb red light...

Good Luck!

Dear Dr. Jose,

Please check the following resources.

Best regards

SM Najim

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3659369/pdf/fpls-04-00140.pdf

http://aobpla.oxfordjournals.org/content/2011/plr030.full

http://www.vliz.be/imisdocs/publications/57074.pdf

Thanks a lot all for the inputs you have given. Cheers!!