I ran across some interesting experiments looking at the resistance to gas vs liquid diffusion of CO2 in plants. Seems my old dept chair had done some studies on the issue.

Salvucci and Bowes 1982.

They compared Myriophyllum grown in air and measured in air vs submersed measured in air or underwater.

The results showed that the plants grown in air did better than those of submersed exposured to the air. They concluded: there is a significant transport resistance in internal leave passage ways to fix CO2.

This means as the water is removed, the gas is much faster at diffusion.
At least an order or two of magnitude faster. But biochemical considerations cannot be overlooked.

Differences between submersed photosynthesis and gas phase aerial types are very apparent.

What is interesting about CO2 mist and exposure to air for brief peroids with submersed growth, is that is appears to get the benefits of each habit without the trade offs biochemically and anatomically.

I think the CO2 mist shows this effect can be sustained, and that the exposure to air concept does indeed work under controlled research condtiions/methods.

Here's a newer paper in full:
Submergence-Induced Morphological, Anatomical, and Biochemical Responses in a Terrestrial Species Affect Gas Diffusion Resistance and Photosynthetic Performance -- Mommer et al. 139 (1): 497 -- PLANT PHYSIOLOGY

Fairly interesting.


Here's the old one from 1982:

ScienceDirect - Aquatic Botany : Photosynthetic and photorespiratory responses of the aerial and submerged leaves of Myriophyllum brasiliense

Today's mighty oak is just yesterday's nut that stood it's ground




Regards,
Tom Barr