Photosynthetic temperature responses of fresh- and brackish- water macrophytes: a review

Data on the temperature dependence of photosynthesis and respiration from 10 different species were reviewed from the literature. A mathematical model incorporating a thermal inactivation equilibrium of an essential enzyme as a controlling factor of the modelled rates [Johnson, F.H., Eyring, H., Stover, B.J., 1974. The theory of rate processes in biology and medicine. Wiley-Interscience, New York, pp. 175- 272.] successfully fitted all large data sets, showing that thermal inactivation is a mechanistic description consistent with the observed patterns in irradiance-saturated photosynthesis (P-m) and dark respiration (DR). General trends could not be observed for the apparent quantum yield (alpha) and light half-saturation constant (K-0.5). We found a positive correlation between latitude and optimal temperature for P-m, which we attributed to the shift in life-cycle (from winter-to summer-active life-cycles) displayed by the waterplants when moving from subtropical to temperate latitudes. Finally, the effect of acclimation on the seasonal extrapolation of parameter estimates was briefly examined. Contrary to what we expected, neither of the two datasets reviewed from the literature supported the existence of a significant seasonal widening of the temperature response curve due to acclimation. [KEYWORDS: production; respiration; latitudinal variation; life-cycle; acclimation Ruppia-maritima l; zostera-marina l; myriophyllum-spicatum l; photon irradiance; light; growth; acclimation; seagrasses;plants; co2]