PHOTOSYNTHETIC, PHOTORESPIRATORY AND RESPIRATORY BEHAVIOR OF 3 SUBMERSED AQUATIC ANGIOSPERMS

The rates of dark respiration, net and apparent photosynthesis and photorespiration in three submersed aquatic macrophytes, viz., Hydrilla verticillata (L.f.) Royle, Vallisneria spiralis L. and Potamogeton pectinatus L., were studied by estimating dissolved and gaseous O2. Among the three species, Hydrilla showed minimum dark and photorespiration and maximum apparent photosynthesis, while Potamogeton showed almost the reverse. The vigorous growth and dominance of Hydrilla and slender growth of Potamogeton in local ponds and lakes of this locality might be ascribed to these differences in physiological behaviour. Vallisneria was intermediate in this respect. Based on the above physiological characteristics, it was inferred that all the above three species are basically C3 plants. There was a gradual decline in physiological processes with increase in leag age in the case of Vallisneria. This age effect was also substantiated from data obtained from induced-ageing experiments. It was concluded that ageing has a similar effect on aquatic submersed macrophytes as in terrestrial plants. © 1979.