THE CONVERSION OF FAT TO CARBOHYDRATE IN THE GERMINATING CASTOR BEAN : III. THE CHEMICAL ANALYSIS, AND CORRELATION WITH RESPIRATORY EXCHANGE.
1. Analyses for fat (ether extract), protein (N x 6.25), sugar including glucose, crude fiber, and ash have been made on all stages of the germinating castor bean up to 250 mm. length of hypocotyl and root system. 2. There is a continual decrease in the amount of fat present in the whole germinating seedling, and a continual increase in the amount of sugar up to about 40 per cent (dry weight) at a hypocotyl length of 80 to 140 mm., after which it decreases as crude fiber (cellulose) increases. The most rapid decrease in fat content coincides roughly with the most rapid increase of sugar. 3. The carbon balance between fat loss and carbohydrate (including fiber) gain is not at all close, except at the very beginning of growth. An undetermined residue occurs, which increases steadily along with the total carbohydrate and accounts for more and more of the carbon. 4. The protein content which in the ungerminated bean is about 26 per cent, at first falls a little and then rather steadily increases to reach nearly 35 per cent (dry) at the last stages studied. The most plausible explanation of this is the occurrence of more and more volatile substance which is lost in drying. 5. The ash increases irregularly but in the end shows about the same ratio of increase as the protein. 6. Respiration studies on several lots of these beans at different stages of germination exhibited the same low respiratory quotients as reported in Paper I. Comparing their composition at the end of the respiration period with that of corresponding stages when the period began, the chemical change can be compared with the respiratory exchange. 7. A trial balance of all the carbon changes including the respiratory carbon and protein carbon is not very satisfactory, because of our ignorance of the undetermined residue. 8. The respiratory quotient found can be accounted for quite satisfactorily on the assumption that two out of six molecules of ricinoleic acid are converted to cane sugar, one to cellulose, and three are oxidized. 9. The oxygen needed to produce the quantities of known carbohydrate found, added to that used for combustion, and the total subtracted from the observed loss from the respired air yields in two experiments a quantity which, combined with the excess carbon, suggests that the undetermined substance may be an oxidation product of pentose.
Pierce
H B
HB
Department of Vital Economics, University of Rochester, Rochester, N. Y.
Sheldon
D E
DE
Murlin
J R
JR