Carbon Dioxide Production by Dry Grain of Zea mays

Use of the gas chromatograph and a mercury-to-glass sealed respirometer adapted for gas syringe sampling, allowed the rapid, accurate characterization of CO2 evolution rates from live and from dead-sterile Zea mays L. grain dried to moisture levels of 12.6 to 1.4%. The live grain at the lowest moisture level showed an elevated rate inconsistent with the exponential increase in rate of CO2 evolution with increasing moisture found for maize with moisture contents from 4 to 12.6%. At the lowest moisture level, rates of CO2 evolution from dead-sterile grain were greater than for live grain. Moisture had no effect on CO2 evolution from dead-sterile grain. Increasing temperature and increasing levels of O2 in the storage atmosphere resulted in increased rates of CO2 evolution from both live and dead-sterile maize. CO2 production rates from live and from dead-sterile grain decreased with increasing storage time, even though respirometer CO2 concentrations were less than 1% at the end of the experiment. Our results indicate that CO2 production is not a dependable measure of respiration in dry seeds. Other experiments indicate that oxygen absorption also is not reliable in maize grain.