Diurnal fluctuations in oxygen release from roots of Acorus calamus Linn in a modeled constructed wetland

Abstract

Oxygen is known to be released from plant roots, but has seldom been quantified for wetland plants. Our study aims to quantify oxygen release from the roots of one wetland species in China, and use this knowledge as a basis for future modeling. We measured diurnal fluctuations in oxygen release from the roots of Acorus calamus Linn in a modeled constructed wetland (CW) using a titanium () citrate buffer. Oxygen release was monitored every two hours. Maximum oxygen release was recorded in the range of 215.2–750.8 μmolg⁻¹h⁻¹ and occurred around 15:00. The maximum value of photosynthetically active radiation (PAR) was in the range of 1281.8–1712.0 mmolm⁻²s⁻¹ and occurred around 13:00. Both the oxygen release rate and PAR were found to approach zero at night. Our results indicate that oxygen release depends largely on light intensity and exhibits a diurnal periodicity with release occurring only during daytime. Rate of root oxygen release varied during the daytime and this temporal variation was well described by the Gaussian function. While further validation is needed, we suggest that the Gaussian function may be used as the basis for modeling root oxygen release in natural and constructed wetlands.

Keywords:

• Wetland plants
• constructed wetlands
• diurnal fluctuation
• photosynthetically active radiation
• oxygen release rate
• Gaussian function

Acknowledgements

The authors gratefully acknowledge Professor Ling Li (The University of Queensland, Australia) for many suggestions and fruitful discussions. This study was supported by the National Natural Science Foundation of China (50979028), and the Ministry of Water Resources of China (200801065).