Comparison of the morphological traits of the submerged macrophyte Potamogeton malaianus from turbid and clear waters in Lake Taihu

Submerged macrophytes growing in clear- and turbid water may develop morphological differences as adaptations to difference light levels. Plant forms altered over generations and longtime are regarded as ecotypes and the changes are assumed to be persistent, even if the plants are returned to their ancestral environment. Specimens of Potamogeton malaianus from clear and turbid water zones of Lake Taihu were compared in their native settings and after transplanting to similar and different environments. Results showed that turbid water forms of P. malaianus had significantly larger shoots with more and longer leaves and more biomass concentrated near the water surface. After transplanting into clear water, the daughter shoots arising from clear or turbid water plants showed no significant differences from their mother shoots, but showed significant differences from each other. After transplanting into turbid water, mother and daughter shoots originating from turbid water plants had similar morphologies, but were significantly different from clear water plants. Plants transplanted from clear water did not survive in turbid water. Our results suggest that P. malaianus forms special ecotype in turbid water, which may help plants maximize their sunlight-harvesting potential and thus might contribute to an observed expansion of the species into turbid water areas of eutrophic lakes.