Radial oxygen loss, photosynthesis, and nutrient removal of 35 wetland plants

The aim of the present study was to test the correlation between radial oxygen loss (ROL), photosynthesis, and nutrient removal based on the hypothesis that ROL was principally a positive physiological process of wetland plants, and was correlated with photosynthesis and nutrient removal. Thirty five emergent wetland plants were used for the measurement of ROL, photosynthesis, and nutrient removal in micro-scale wetlands in a climate chamber. Significant differences among thirty five species were tested in ROL, photosynthetic rate, and nutrient removal rates. ROL was positively correlated with photosynthetic rate (P = 0.000), transpiration rate (P = 0.005), root activity (P = 0.000), root biomass of D ≤ 1 mm (P = 0.002), above-ground biomass (P = 0.030), leaf biomass (P = 0.023), root porosity (P = 0.000), maximum root length (P = 0.011), and removal rates of TN and TP (P = 0.000, 0.002), while negatively related to root biomass of D ≥ 3 mm, and root longevity (P = 0.022, 0.007). All the indices which were positively correlated with ROL, also positively correlated with plant growth. The results suggest that ROL may be an active physiological process or at least involves physiological processes of wetland plants. Significant differences existed among different wetland plants in ROL, photosynthesis, and nutrient removal, which should be considered in plant selection for constructed wetlands.

► Thirty-five wetland plants were studied in microcosms in laboratory condition.
► ROL, photosynthesis, and nutrient removal were investigated for the plants.
► Correlations between above indices were analyzed.
► Hypothesis: ROL was an active process relating to photosynthesis and nutrient removal.