THE MEASUREMENT OF PHOTOSYNTHETIC PARAMENTERS OF SUBMERSED MACROPHYTES WITH AIMS TO EXPLORE THE PLANT DISTRIBUTION DEPTH IN ERHAI LAKE

Photosynthesis is vital physiological process producing carbohydrate for the growth and distribution of submersed macrophytes, and thus may closely relate to the plant distribution depth. To clarify the differences of photosynthetic parameters and their relevance to the colonization depths of submersed macrophytes, we measured the light compensation and saturation points, photosynthetic rate and dark respiration of 15 submerged macrophytes, using a liquid-phase oxygen electrode, and investigated the plants distribution depth in Erhai Lake, China. The results showed that the photosynthetic rate ranged from 2.8 to 18.1 μmol O₂/(g DW·h), the dark respiration rate ranged from 0.3 to 2.0 μmol O₂/(g DW·h), the light compensation point ranged from 6.3 to18.1 μE/(m²·s), the light saturation point ranged from 55.6 to 441.5 μE/(m²·s). The plants had significant differences in the photosynthetic parameters. Based on a field survey of the plant distribution depth, the light compensation and saturation points of the submerged macrophytes were negatively correlated with their distribution depths. V. natans had the lowest light compensation and saturation points, and were more suitable to grow in deeper water where the experienced low light stress, and thus V. natans could be taken as a pioneer species for the restoration of submerged macrophytes in eutrophic lakes.