Quantitative Study of Ethylene Production in Relation to Respiration of Pears

A quantitative study of ethylene production in relation to the respiration of pears has been made. The emanation of ethylene in air at 20⚬ C., as well as at higher and lower temperatures in modified atmospheres, has been studied. 2. In fruit in air at 20⚬ C. the rate of ethylene production increases during the climacteric rise in respiration, reaches a peak at the respiratory climax, then declines during the post-climacteric period. During the climacteric rise, ethylene production increases seven- to eighty-fold, while rate of respiration approximately doubles. 3. Each variety was found to have a characteristic maximum rate of production. The maximum rate for Bartlett, a variety which maintains its capacity to ripen for only a short period of time when kept at a storage temperature of 0⚬ C., is 3.25-4.48 ml. per kg.-day. The maximum rate for Anjou, a variety which maintains its capacity to ripen for a long period of time when kept at cold storage temperatures, is 0.57-0.78 ml. per kg.-day. The maximum rate of respiration for Bartlett is approximately double that for Anjou. 4. Under anaerobic conditions, the production of ethylene is either greatly retarded or entirely inhibited. In the fruits used for these experiments, there was found but little difference in the production of CO2 under aerobic and anaerobic conditions. 5. The maximum rate of ethylene production occurs at 20⚬ C. At higher temperatures production decreases and is totally inhibited at 40⚬ C. Respiratory activity as measured by either CO2 production or O2 consumption is greatly accelerated between 20⚬ and 40⚬ C.