Growth and turion formation of Potamogeton crispus in response to different phosphorus concentrations in water

Abstract

The vegetative growth and turion formation of Potamogeton crispus, a submersed aquatic macrophyte, was investigated under a range of phosphorus (P) concentrations (0. 025, 0. 25, 2. 5 and 25 mg P L⁻¹) in the ambient water free of algae, aiming to identify the responses of submersed aquatic macrophytes to nutrient enrichment, a common eutrophication problem in China and worldwide. Plant growth was not affected by different P concentrations in terms of biomass accumulation of stems and leaves. However, the contents of chlorophyll a and starch in plants decreased with increasing water P levels, whereas chlorophyll b and carotenoids declined with P level ranging from 0. 025 to 2. 5 mg P L⁻¹. The soluble sugar content decreased when water P concentration increased up to 2. 5 mg L⁻¹. The P content in plants increased with increasing water P levels, whereas plant N content decreased and soluble protein increased when water P concentration increased over 0. 25 mg L⁻¹, implying that P. crispus may have modified its metabolism to adapt to water P availability. When P concentration increased to 25 mg L⁻¹, the number and dry matter production of turions per plant decreased significantly. Meanwhile, there was a significant reduction in turion weight and the accumulations of soluble sugar and starch in turion, when water P concentration was over 0. 25 mg L⁻¹. The results suggest that turion formation in P. crispus is sensitive to P concentration in the ambient water, and high P levels may lead to decreases in P. crispus populations due to the decline in turion production.