Hi Hery,

in principal, all cellular processes in aquatic plant cells do not differ that much from that of terrestrial plants. Hence, aquatic macrophytes (I think that's what you are after?) depend on the same amount of CO2 as terretrial plants.

However, solubility of CO2 in water - especially in lakes during summer, and the availabilities of CO2 in ambient air condition differs tremediously!

Gas equations will tell you that CO2 becomes limiting for plant growth in warm waters (tropics, subtropics), where aquatic plant diversity is at its maximum.

This, can probably explaint by the ability of aquatic macrophytes (for algae it is not known) that perform CAM metabolism besides C3 to nurrish on carbonates instead of gaseous CO2. The advantage of CAM is that HCO3- reamins a soluble ion, even under elevated temperatures!

There are several reports on CAM/C4-like metabolism in aquatic macrophytes (e.g. in Isoetes, aquatic Crassula, Hydrilla verticillata, Egeria densa, Lobelia, Littorella etc.

There is even one report on a C4-like metabolism in a unicellular algae... but I forgot the reference. You will find it, in case you need it.

I think it is a tricky question. The biodiversity under the water is very large and every organism has its own needs and it is difficult to generalize

Hy Hery

I suggest you to read this reviews. There is everything you need to know about adaptations and physiology of aquatic plants:

N. Rascio. (2002) The Underwater Life of Secondary Aquatic Plants: some problems and solutions - Critical Rev. in Plant Sciences, 21(4): 401 - 427

As an addendum to Dierk Wankes answer: The report on C4 metabolism in phytoplankton is by John Reinfelder et al. from the Morel lab in Princeton. Here is a link to the original paper from 2004:

http://www.plantphysiol.org/content/135/4/2106.long

At the time, this was heavily debated.

But generally, C4 metabolism is just one of the many possible ways that phytoplankton use to increase carbon uptake by the cell. These are collectively known as carbon concentrating mechanisms (CCM). Often, the enzyme carbonic anhydrase, which sppeds up the interconversion between CO2 and HCO3- is involved. See, for example the review by Marion Giordano et al.:

http://www.researchgate.net/publication/7876354_CO2_concentrating_mechanisms_in_algae_mechanisms_environmental_modulation_and_evolution/file/9fcfd5080da7fca407.pdf

Article CO2 concentrating mechanisms in Algae: Mechanisms, environme...

Pak Hery... maksudnya gimana? jadi tumbuhan akuatik lebih banyak menyerap CO2 daripada tumbuhan teristrial, berarti tumb akuatik lebih banyak menghasilkan O2 begitu ya.. pak?