STRUCTURE, BIOMASS AND SEASONAL-CHANGES IN BIOMASS OF NYMPHOIDES-PELTATA (GMEL) O KUNTZE (MENYANTHACEAE) - PRELIMINARY-STUDY

A study has been made on structure and biomass of Nymphoides peltata (Gmel.) O Kuntze in an old river branch of the river Waal (The Netherlands). Some notes have been made on the ecology and distribution of the species. The external morphology of the species has been described. Correlations have been calculated between parameters such as leaf surface and lenght of the different plant parts with their ash-free dry weight. The mean ash-free dry weight of the flowers including the pedicels for each developmental stage has been determined. Biomass samples have been taken during a whole year in the centre of a dense Nymphoides bed, so that the seasonal changes in biomass per m2 could be followed. In contrast with the other plant parts, the roots showed a very high percentage of ash in June when root biomass is lowest; in winter the roots show absolutely and relatively the highest biomass. The mean ratio aboveground biomass-underground biomass was highest at the end of June (3.20) and lowest in January (0.27). The correlation between leaf surface (per m2) and total biomass (per m2) can be described by a quadratic regression equation. As variation in time of nearly all measurements was large, more information is needed to describe the changes in biomass on the sampling site more exactly. The general reliability of the results of the study must also be tested in other localities. © 1979.