t o Dec, 1910.] Bitter Pit and the Enzymes of the Apple. 805 



BITTER PIT AND THE ENZYMES OF THE APPLE. 



Jean White, D.Sc, Lecturer on Botany in the Melbourne University. 



The question of Bitter Pit in apples has Lately been occupying the at- 

 tention of various Agricultural Departments in" different parts of the 

 world. 



A short account of what has been regarded as the correct explanation 

 of this disease was quoted by Mr. D. McAlpine in the Journal for April, 

 1 910. This explanation was first put forward by Mr. Pole Evans 

 {Technical Bulletin, No. 1, Transvaal Department of Agriculture), wh(; 

 concluded that the disease was due to the sudden cessation at night of 

 transpiration, causing cells near the surface to accumulate so much water 

 as to produce their rupture, and a consequent decay spreading to neigh- 

 bouring cells. This theory is not based upon any sound experimental 

 evidence, and entirely fails to explain not only the incidence of the 

 disease, but also why certain varieties are more liable than others, why it 

 is usually more developed at the upper end of the fruit, and why it does 

 not occur in other stored succulent fruits, such as melons or bananas. 



A paper on this subject was also contributed by Mr. C. P. Lounsbury, 

 in the Agricultural Journal of the Cape of Good Hope, August, 19 10, 

 which he says consists for the most part of extracts from a paper by Mr. 

 G. Massee in the Kew Bulletin, No 6. 



As it was considered possible that a microscopic examination of diseased 

 fruit might yield some facts of interest, a supply of material was obtained 

 from the Government Cool Stores. Sections cut through the pitted areas, 

 which are tough and porous, show that the surface parenchyma cells are 

 not altered in any way, and as a rule there are about ten to twelve layers 

 of these normal cells above the affected ones. 



The affected cells are seen to be larger than the normal cells surround- 

 ing them, their outline being also more irregular, and the cell wall broken 

 ill places. Except for a small amount of protoplasmic contents which 

 is adherent to the cell wall, and a large number of starch grains which 

 are most abundant near the periphery, the cells are apparently empty. 

 Treatment of the normal cells with aqueous solution of iodine shows no 

 sign of the presence of starch grains, so that, in the living healthy cells, 

 any starch which may be produced during assimilatory activity must be 

 either immediately hydrolysed to form sugar by some diastatic enzyme, 

 or worked up into other compounds by some metabolic processes. 



The presence of so much starch in the diseased cells suggested a pos- 

 sible connexion between the disease and the occurrence of enzymes in the 

 cells of the apple, and as no references to any work relating to this sub- 

 ject could be found, I performed a series of experiments on the pulp of 

 sound, healthy apples, on the sound pulp of pitted apples, and on the 

 cells composing the affected areas of these fruits. All the specimens 

 examined had been stored for five months. 



The pulp of these fruits was minced up in a coffee grinder, care being 

 taken to insure sterilization after each operation, and the enzymes were 

 j)recipitated in the same manner as was followed in my paper on " The 

 ferments and latent life of resting .seeds," published in the Proceedings 

 of the Royal Society of London, B. vol. 81, 1909. In every instance, 

 the enzyme solutions were found to be neutral, and the antiseptic employed 

 was chloroform. 



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