Ozone gas was generated by passing oxygen gas across a UV
lamp in an ozone generator (Systrocom, India). The O3 generator
was connected to air delivery system of OTCs and additional O3
over the ambient was blown into the chamber for elevated O3
concentration through controlled system connected with solenoid
valve. Ozone monitoring was done above the crop canopy for 8 h
from 9:30 to 4:30 h through an inert Teflon tube from sowing to
maturity using UV absorption photometric ambient O3 analyzer
(Model APOA 370, HORIBA Ltd., Japan). The variations in O3 and
CO2 concentrations and environmental conditions in OTCs
throughout the study period (November 2010–February 2011)
are given in Kumari and Agrawal (2014). The average daytime
ambient O3 concentration was 49.66 ppb.