[Pboc. Eoy. Soc. Victoria, 27 (N.S.), Part II., 1914]. 



Art. XXI II. — On Bitter Pit and Sensitivity of Apples to 

 liaison . 



By ALFRED J. KWAHT, l).8c., Ph.D. 



(Professor of Botany and Plant fhysiolog-y in the Melbourne University). 



[4th Papkk]. 

 [Read tlitli Noveuil)er, IDUJ. 



In 1913 Rothera and Greenwood made a direct attempt to test 

 the poisoning theory of Bitter Pit, on the line that if the non- 

 solution of the starch grains usually shown in Bitter Pit tissue is 

 due to the action of the poison, a diastase solution after contact 

 with Bitter Pit tissue should have its diastatic activit}- retarded. 

 They stated, however, that witli malt diastase and Taka diastase an 

 accelerating action was shown. In the Proceedings of the Royal 

 Society of Victoria, Vol. 26, p. 233, I showed, however, that they 

 had overlooked the influence of the presence of tannic acid, and 

 that even a short contact of 10 c.c. of 1 % Taka diastase 

 with 20 grams of pounded apple pulp distinctly retarded the 

 diastatic activity of the filtered extract. It is well known that 

 tannic acid retards diastatic action, and this was supposed to be due 

 to a direct action on the diastase. I showed, however, that tannic 

 acid, even when dilute, precipitates starch from a watery solution, 

 and thence concluded that the action was rather on the starch than 

 ■on the diastase. This is borne out by the fact that the precipitating 

 action is less pronounced at high temperatures, and that under 

 these circumstances the retarding action of the tannic acid is also 

 relatively less pronounced. 



In replying to my criticism, Rothera and Breidahl reaflirni the 

 existence of an accelerating action. This might be obtained under 

 the following conditions : — (1) If a resistant and very active diastase 

 such as Taka diastase is used in relatively large amount. (2) If the 

 tests are made at high temperatures. (3) If dry bitter pit pulp in 

 Avhich the tannic acid has been oxidised is compaied with fresh pulp 

 rich in tannic acid. 



I found that using equal volumes of 1 % taka diastase or malt 

 diastase, of 1 % starch solution, and of tannic acid, the latter 

 retarded the hydrolysis of starch down to concentrations of 0.005 to 



