TEMPERATURES OF SMALL FRUITS WHEN PICKED 



NEIL E. STEVENS and R. B. WILCOX 



Bureau of Plant Industry, U. S. Department of Agriculture 



It has been known for over a century ((6), p. 538) that certain 

 plant parts may reach a temperature markedly above that of 

 the air. Accurate observations on this temperature relation 

 have been made by several investigators.^ There seems to be 

 no record in available literature, however, of the easily observed 

 fact that many small fruits attain on clear days, largely through 

 insolation, a temperature much higher than that of the air. 

 This condition was first noted in cranberries {Vaccinium niacro- 

 carpon Ait.^ during the fall of 1916. As opportunity offered in 

 connection with ether work during the summer of 1917, the 

 writers have made observations on the temperature of various 

 small fruits in relation to air temperature at picking time. The 

 data thus accumulated are thought to be of some botanical 

 interest. They are of particular significance, also, in relation to 

 the decay of these fruits in transit and on the market. This 

 relation does not seem to have been applied generally to horti- 

 cultural practice; however, the fact that small fruits, notably 

 strawberries, keep better if picked when cold than if picked 

 later in the day, when warm, has been demonstrated by the 

 writers (10).^ 



1 The studies of Ehlers on leaves of Pinus may be cited as a recent example of 

 this type of work. His paper (3) gives a review of the more important publica- 

 tions on the subject, with special reference to those dealing with leaf tempera- 

 ture. Some of the more general papers are mentioned by Pfeffer (7, vol. 3, p. 

 378-381). No attempt at a complete bibliography is made in the present paper. 



2 The nomenclature used is in general that of Gray's Manual of Botany, 

 Seventh Edition, 1908. 



3 Powell (Powell, G. Harold, Bur. PL Ind. Bui. no. 40, 1903) calls attention 

 to the fact that peaches picked and loaded into cars during the middle of the day 

 are warmer, and carry to market less well, than those picked early in the morn- 

 ing. He does not note, however, that in the middle of the day the fruit is actu- 

 ally warmer than the air. 



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