1094 AGRICULTURAL liOTANV, CHEMISTRY AND I'll VSIOI,0(tY OF PLANTS 



as also between this activity and tlie total quantity of sugar. Thus, with 

 the inciease of activity of amylase, the proportion of total sugar and of 

 non-reducing sugar also increases, except in the cases where certain tixbers, 

 owing to their more intense respiration, contain less sugar than tubers with 

 amylase of equal activity bi^t weaker respiration. 



The knowledge of the activity of the amylase is of great importance from 

 the point of view of storage of the potatoes, inasmuch as those potatoes which 

 contain amylases of higher activity are rich in sugar or their respiration is 

 more intense. It is known, however, from the investigations of W. Henne- 

 BERG, that the tubers with a high sugar content are more liable to rot, and 

 that on the other hand tubers with more intense respiration imdergo a 

 larger reduction of the starch content. 



Among the tubers subjected to low temperature, increase in the sugar 

 content occurs in those in which the amylases possess greater activity. 



II. — The results by means of which Doby determined the character- 

 istic properties of amylase in potatoes in the resting state afforded the poss- 

 ibility of continuing enquiries into this ciuestion. Tlie experiments were 

 carried out on carefully chosen potatoes from the test fields of the Royal 

 Hungarian Station of Plant Physiology and Pathology. A parallel anal- 

 ysis was made of ii specimens of healthy and diseased potatoes and 9 spe- 

 cimens of exclusively diseased potatoes, along 2 lines : it was ascertained in 

 what way the proportion of amylase is modified fiist of all in the potato in a: 

 state of rest and afterwards in the expressed juice of the tubers and dur- 

 ing its storage. 



From these researches, it is concluded that a portion of the amylase is 

 present in the potato in the form of zymogene which is transformed into 

 an active enzyme towards the end of the resting stage ; this transformation, 

 however, takes place much more rapidly if the juice of the tubers is kept in 

 the presence of an antiseptic. Ford and Gutrie, and also van L.-^.R, have 

 endeavoured to determine the agents which produce this metamorphosis. 

 They immersed the dust of germinating barley in papaine, which increased 

 the activity of the amylase. There is reason to believe therefore that in 

 the potato also, the action oft he proteolytic enz3anes slowly transforms the 

 zymogene of the amylase into free enzyme during the winter rest; this trans- 

 formation is more rapid in the expressed juice after the cell walls have been 

 destroyed, from which it follows that the action of the amylase becomes 

 stronger in the juice antisepticalh^ stored. I^p to the middle of the period of 

 rest, however, the quantity of zymogene is small ; it only begins to increase 

 at the beginning of January, and from this time onwards increased activity 

 of the stored juice may be observed. It is well known that the amylase 

 of the potato is extremely sensitive. It follows that the greater the ini- 

 tial activity of the potato juice, the less this activity increases during the 

 storage of the juice, that is to say, the more quickly it disappears. While 

 the quantity of enzyme in the juice is small and that of zymogene large, so 

 many new enzymes are formed by autolysis from this latter, that a total 

 increase of them is observable, in spite of the weakening and disappearance 

 ol the enzymes already present. On the other hand, towards the spring, the 



