1918] Kendall: Abscission of Flowers and Fruits in Solanaceae 381 



e. EXPERIMENTS ON THE AMOUNT OP SUGAR IN THE STEM 

 AND PEDICEL OF NICOTIAN A DURING ABSCISSION 



After several experiments, all of which indicated the results ob- 

 tained below, the following experiment was performed. Experiment 

 2a was devised to show the change in the amount of sugar which 

 occurs in the tissues of the pedicel during abscission. Experiment 26 

 was intended to show this same difference in a restricted region of the 

 stem just proximal to the separation layer. 



Experiment 2a. Lot A included 200 pedicels of flowers which had 

 fallen a few minutes before being collected as a result of being sub- 

 jected to illuminating gas. Lot B included 200 pedicels of flowers 

 picked at the same time as those making up Lot A, but in which no 

 abscission was induced. The water extracts made with 10 cc. from 

 equal weights of the two lots were tested with surplus Fehlings solu- 

 tion. The precipitates formed upon boiling weighed: 



A 68 mg. 



B , 95 mg. 



Experiment 2b. This experiment was carried out in the same man- 

 ner as experiment 2a, but the precipitates in this case were of such 

 small quantity that no attempt was made to get actual figures as to 

 their weights. It was clear, however, merely from an examination of 

 the filter paper, that there was more precipitate in B than in A — just 

 the reverse of Experiment 2a. The difference was evidently not as 

 great as in the latter experiment. 



Experiment 2a seems to indicate that during abscission there is a 

 reduction of nearly one-third the normal amount of sugar in the 

 pedicel. Other preliminary experiments performed as abscission was 

 starting showed only a slight reduction in the amount of sugar in the 

 pedicel. Thus possibly the withdrawal of sugar commences with the 

 start of abscission. Experiment 2b indicates that there is probably a 

 slight increase in the amount of sugar in the limited region proximal 

 to the separation during abscission. It is possible that most of the 

 withdrawn sugar is used as a source for the energy required in the 

 active process of cell separation. The slight increase proximal to the 

 separation layer also shows that there is probably an increase in cell 

 turgor in the actual tissues which contain the separation layer, due 

 to the conversion of starch into sugar. 



