Respiration in Strawberry Fruits

1. An exceedingly sensitive respirometer is described, by which the rate of respiration of a single strawberry over half a minute of time can easily be measured. The method of operation is explained. Large sources of error inherent in an impracticable method of use of the instrument, but one which plausibly suggests itself, are pointed out. 2. The amount of oxygen used by the Missionary strawberry at temperatures of from 5⚬ to 40⚬C. is determined. A curve of this respiratory activity is presented. 3. Amounts of oxygen required by strawberries during shipment in carload lots is calculated. Assuming that the oxygen so required is used to oxidize glucose, the amount of heat thereby generated is shown in terms of pounds of ice which it would melt. 4. The maximum initial rate at which strawberries respire is 36.5⚬C. At the higher temperatures (35⚬, 36.5⚬, 37.5⚬, and 40⚬C.) respiration quickly falls. As a result, the maximum rate varies with the time over which it is considered. 5. The temperature coefficient for the respiration of the Missionary strawberry is 2.5 for temperatures below 25⚬C. 6. A temporary increase in the rate of strawberry respiration occurs as a result of exposure to dry air. This rate later declines. 7. Strawberries are very effectively protected from water loss in dry air. The loss is about 2 per cent by weight at the end of 50 hours in dry air, compared with a loss of 1.1 per cent in moist air. 8. Strawberries have a very constant water content, the amount of which is approximately 89.5 to 90 per cent. 9. Deterioration of strawberries in storage at ice-box temperatures as measured by loss in weight is about 4.5 to 5 per cent in two days and 10 per cent in four days. 10. The Gibson strawberry, northern grown, has a much higher rate of respiration at low temperatures than the Missionary strawberry, which is southern grown. 11. Much of the data available upon respiration is inconsistent with the interpretations made of it. This is because of inability so far to reckon in given instances with all the factors affecting respiration. 12. Acid content of strawberries declines as they pass from the green stage to a stage of ripeness just preceding actual deterioration. 13. The respiratory ratio (CO2/O2) for ripe fruits is found to be greater than one. An approximate value of 1.2 is given for this ratio. The CO2/O2 ratio was determined with the Krajnik apparatus. 14. Ethylene gas in concentrations of 1:1000, 1:1500, and 1:2000 is without effect in hastening the visible changes incident to ripening in strawberries.