Affiliations: Research Center for Eco-environmental Sciences ,
Chinese Academy of Sciences, Beijing, 100080,China. E-mail:jinmh@sina.com
Abstract: The impacts of different O_3 concentration on the biomass and yield
of rice were studied by using OTC-1 open-top chambers. Experimental treatments
included the activated charcoal-filtered air (CFA), 50nl/L (CF50), 100nl/L
(CF100) and 200nl/L (CF200) concentrations of O_3. The O_3 treatments
significantly decreased the total biomass per plant. The elevated O_3 exposure
resulted in a more decrease in the root growth than in the shoot growth.
Assessments of yield characteristics at the final harvest revealed an O_3 -
induced decrease in the number of grains per plant, resulting from fewer ears
per plant, fewer grains per ear and more unfilled grains per ear. The 1000
grain dry weight and the harvest index (HI) were not changed significantly
under 50nL/L or 100nL/L O_3 exposure, but reduced by 17.0% and 4.8% by 200nL/L
O_3 treatment, respectively. Compared to the CFA treatment, CF50, CF100 and
CF200 treatments caused a 8.2%, 26.1%, 49.1% decrease of the grain yield per
plant, and a 14.2%, 31.7%, 51.7% decrease of the total biomass per plant,
respectively. Linear regression showed that the 7h-daily mean O_3 concentration
exposure for 3 months (July-September) and AOT40 (cumulative exposure
accumulation over threshold 40 nL/L) were well correlated with the relative
grain yield. A yield loss of 10% was estimated to be at 46.9nl/L O_3 for
7h-daily mean O3 concentration exposure or at 12930 nl/(L·h )O3 for
AOT40.
