Effects of the diurnal variation of sunlight on water quality and the physiology of Nymphaea tetragona

Abstract

Date of this study was 10, 15, and 20 July 2010, and the location was the river Huichang located in Wenzhou China. A purifying tank containing Nymphaea tetragona was used to treat polluted river water. This study took place from 08:00 to 18:00 and in that period the physiological parameters of the plant and the water quality were analyzed. The results indicated that higher sunlight intensity increased the rate of photosynthesis (Pn) and transpiration (Tr) and the resistant enzymes activity of the plant. Sunlight also decreased the cations (Al³⁺, Fe³⁺, Ca²⁺), anions (Cl⁻, , ), biochemical oxygen demand, total nitrogen, and dissolved phosphorus of the water. Pn of the plant showed a double peak due to the decrease in photosynthesis at midday, while Tr showed a single peak. Pn and Tr were highest between 10:00 and 14:00, while cations and anions decreased during this time. The diurnal variation of sunlight influenced the Tr and Pn, the anion and cation absorption, and the oxygen efflux of the plant's roots. The dissolved oxygen change was closely associated with the degradation and decomposition of water pollutants and the absorption variation of anions and cations was correlated to peroxidase and catalase activities of the plant.

Keywords:

• Nymphaea tetragona
• diurnal variation
• physiological characteristic
• water quality

Acknowledgments

This work was supported by the National Scientific and Technological Major Program of China (No. 2009ZX07317-006) and the Scientific Committee Key Program of Shanghai (No. 062312019). We gratefully acknowledge the School of Resource and Environment Sciences of East China Normal University for kindly providing facilities for this study.