Correlation between diurnal variation of the physiological status of pontederia cordata and nitrogen and phosphorus removals of the polluted water

Pontederia cordata was cultivated in 9 tanks with various planting densities (densities: 5, 10, 20) to investigate diurnal variation of physiological status of the plants including peroxidase (POD) and catalase (CAT) activities of the roots, soluble proteins (SP), chlorophyll (Chl) contents of the leaves and main physical and chemical traits of the effluents. Morphological dimensions, tillers, roots densities, biomass and nitrogen (N) and phosphorus (P) accumulation of the plants are measured. Correlation between diurnal variation of the physiological status of the plants and N and P removals of the effluents is analyzed, and effects of planting densities are researched. Results show POD and CAT activities of the roots, Chla, Chb and SP contents of the leaves have positive correlations with NH₄⁺-N and soluble P removals of the effluents. In the tanks with higher planting densities, the plants are higher and bigger, and have more tillers, roots densities, biomass and N and P accumulation, higher Chla, Chb and SP contents of the leaves and NH₄⁺-N and soluble P removals of the effluents, while POD and CAT activities of the roots declined. With stronger sunlight, POD and CAT activities of the roots, Chla, Chb and SP contents of the leaves, NH₄⁺-N and soluble P removals of the effluents all increase. Chla, Chlb and SP contents of the leaves and the outlet DO show double-peak styles at about 12:00 pm and 14:00 pm. In 10:00 am~14:00 pm, CAT and POD activities of the roots, Chla, Chlb and SP contents of the leaves, NH₄⁺-N and soluble P removals of the effluents all exceeded the other times at the day.