Ah, I share a similar interest. Unfortunately, there are not many good aquatic plant physiology books out there.
1) I would refer you to Aquatic Biology the journal. Excellent work.
2) THE BIOLOGY OF AQUATIC PLANTS, by H. Schenck. 2003. 162 pp.
(Published by Koeltz Scientific Books, Herrnwaldstr. 6, D61462 Koenigstein, Germany. ISBN 3-906166-11-2. $57.00 plus S/H. Email: [email protected]
3) Introduction to Freshwater Vegetation by Donald N Reimer Krieger Publications
4) The Biology of Aquatic Vascular Plants by C.D. Sculthorpe
5) Other journals:
Journal of Phycology
Limnology and Oceanography
Journal of Plankton Research
Archiv für Hydrobiologie
Journal of Aquatic Plant Management
Journal of Freshwater Ecology
Journal of Applied Phycology
Australian Journal of Marine and Freshwater Research
Good luck. Happy to discuss physiology concepts here.