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 CO(2) 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 CO(2) evolution with increasing moisture found for maize with moisture contents from 4 to 12.6%. At the lowest moisture level, rates of CO(2) evolution from dead-sterile grain were greater than for live grain. Moisture had no effect on CO(2) evolution from dead-sterile grain. Increasing temperature and increasing levels of O(2) in the storage atmosphere resulted in increased rates of CO(2) evolution from both live and dead-sterile maize. CO(2) production rates from live and from dead-sterile grain decreased with increasing storage time, even though respirometer CO(2) concentrations were less than 1% at the end of the experiment. Our results indicate that CO(2) production is not a dependable measure of respiration in dry seeds. Other experiments indicate that oxygen absorption also is not reliable in maize grain.