A chamber system for exposing rice (Oryza sativa L.) to ozone in a paddy field

Abstract

A field exposure chamber system was constructed in a paddy field. The system consisted of four ozone generators, five exposure chambers equipped with ventilation fans on both ends, and an ozone measurement and control system. Rice plants were exposed to ozone in the exposure chambers for the whole growing season. The ozone concentration in each chamber was maintained in a constant proportion to ambient ozone. The horizontal distribution of ozone concentration within a chamber showed ±10%, of variation with the lowest values at the centre and both ends of the chamber. Wind velocity showed a similar horizontal distribution as ozone but with a greater variation among the locations within a chamber. Diurnal as well as seasonal changes of ozone concentration in the chambers followed the targeted level rather closely except for several occasions of power failure or system malfunctioning. Temperature in the chambers was c. 1 °C higher in the daytime and 0.34 °C higher on daily average than in the field outside. Light flux density in the chambers was reduced to 75% of that outside with little seasonal variation. These results indicated a satisfactory performance of the field exposure chamber system for its intended use. Copyright © 1994, Wiley Blackwell. All rights reserved