POPULAR SCIENCE 619 



apples. The higher the respiration number the quicker the 

 ripening process and the shorter the time the fruit can be kept. 



From the equation found by Gore one can of course calcu- 

 late the temperature coefficient. He gives a value for Q 10 

 of 2-377, which is in agreement with the Van't Hoff rule. The 

 maturation velocity at 8° C. is double that at o° C. and at 16 C. 

 four times that at o° C, a result agreeing with that found by 

 the experiments of others. 1 



It is obvious therefore that cold storage offers a good 

 means for preservation of fruit. However, the same chemical 

 processes occur as at higher temperatures. 2 The cooling causes 

 only a slowing down and not a disturbance of the normal 

 processes, but whether this can be accepted as a general rule 

 is doubtful. For example, Molisch 3 points out that the dif- 

 ferent processes in plant organs are inter-related, and if the 

 velocities with which these processes occur are altered in 

 different degrees by temperature, the equilibrium is disturbed. 

 In this way he explains the sweetening of potatoes at tempera- 

 tures just above o° C. ; the potatoes form sugar from starch, and 

 the sugar is used in respiration. If the temperature is lowered, 

 sugar formation and respiration do not decrease to the same 

 extent, sugar formation being reduced much less than respira- 

 tion, the consequence of which is the sweetening of the tuber. 



Thus it will be seen that the respiration number 

 affords a convenient index for ascertaining the keeping possi- 

 bilities. Another index which perhaps is still simpler is the 

 temperature difference between the fruit and the atmosphere 

 in the store. If fruit at say 15 C. is introduced into a cold 

 store at, for example, i° C, the temperature of the fruit will 

 fall at a rate depending on the dimensions, spacing, and thermal 

 conductivity of the fruit, and the condition of the air in the 

 cooling chamber, until an equilibrium is reached after two or 

 three days. This equilibrium temperature lies, however, one or 

 two degrees higher than that of the chamber. This tempera- 

 ture difference is a characteristic of the different fruits, so that 

 soft fruit which matures most quickly shows the greatest differ- 



1 E.g. Buison, " De l'emploi de froid dans la conservation des fruits," 

 Dindustrie frigorifique, 1 9 1 2, p. 165. 



* Gore, Proc. Second International Cold Congress in Vienna, 19 10, vol. ii. p. 348. 



8 Untersuchungen iiber das Erfrieren von Pflanzen, Jena, 1897 ; Pfianzen- 

 physiologie als Theorie der Gdrtnerei, 2te Auf, Jena, 1918, 



