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.