A proposal for the equivalence between the rates of net photosynthesis and growth rate constants for submerged aquatic plants

The mathematical prediction of the growth of submerged macrophytes provides direct inference in harvest management, estimation of habitat structuring, and calculation of incidence areas, in function to the main environmental constraints. The aim of this study was to enable us the equivalence between the liquid photosynthetic rates (obtained from the light and dark flasks method) and the growth rates derived from first order models applied to aquatic plants cultures. The association allows the achievement of the values of the growth rates (mu) due to short-term environmental changes, usually well evidenced by the net photosynthetic rates (net primary production; NPP), increasing the accuracy of the growth model. Growth experiments were conducted with two submerged specimens. Using the results of the: (i) carbon content of the plants tissues, (ii) NPP of incubations (light and dark bottles method) and (iii) biomass of cultures growths, it was feasible to verify the range of variation of NPP (coefficient of variation: 62%) and mu values, and establish the calculations for the equivalence of these two parameters. Thus, changes in environmental conditions, including specific and short-term events, can be readily transformed to the mu values, improving the accuracy of the growth simulation of submerged aquatic plants.