Influence of Certain Carbohydrates on Green Plants 41 



TABLE 16. Influence of Glucose and Saccharose on Growth of Vetch in 



Water Culture 



(Duration, twenty-five days. Weight of seed, 30 miUigrams) 



Culture solution 



Number 



of 

 plants 



Dry 

 weight 

 of tops 

 (miUi- 

 grams) 



Dry 



weight 

 of roots 

 (miUi- 

 grams) 



Total 

 dry 

 weight 

 (miUi- 

 grams) 



Gain 

 or loss 

 in weight 

 (miUi- 

 grams; 



Sugar 

 absorbed 

 (miUi- 

 grams) 



Check (no sugar) < 2 



2 

 ♦1 



1 

 1 

 2 



2 

 1 



62 

 25 

 52 



49 

 81 

 80 

 60 



9.0 ; 71.0 



+ 11.0 

 — 1.5 

 + 29.0 

 +27.0 

 +52.0 

 +70.0 

 +46.0 





3.5 



7.0 



8.0 



31.0 



50.0 



16.0 



28.5 

 59.0 

 57.0 

 112.0 

 130.0 

 76.0 





Glucose < 2 



Saccharose i t2 



Its 



39.0 

 36.0 



85.7 

 64.6 

 55.0 



* 66 m'lligrams of reducing sugar present, 

 t 50 milligrams of reducing sugar present, 

 j 88 milligrams of reducing sugar present. 



INFLUENCE OF EQUIMOLECULAR SOLUTIONS OF GLUCOSE, MALTOSE, AND 



SACCHAROSE 



In all the preceding experiments in which the comparative effects of 

 the different sugars were to be noted, the sugars were used in approxi- 

 mately carbon-equivalent solutions, the concentrations being 1 or 2 

 per cent. Saccharose seemed to be utilized more readily than glucose, 

 and glucose more readily than maltose. Lactose, as was to be expected, 

 proved of the least benefit. Since the carbon-equivalent solutions are 

 not aU equimolecular, the osmotic relations of the disaccharides and the 

 hexoses are different. As akeady stated, the 2-per-cent glucose solution 

 is equivalent to a 0.111 gram molecular solution, while the 2-per-cent 

 disaccharide is equivalent to a 0.058 gram molecular solution. The 

 osmotic pressm'e (theoretical) of the glucose solution is therefore approxi- 

 mately twdce as great as that of the disaccharide, and, as compared with 

 the disaccharide, glucose might be expected to act disadvantageously 

 to the growth of the plants because of this higher osmotic pressm'e. The 

 increased growth with increase in concentration above 2 per cent of 

 glucose indicates, however, that the 2-per-cent glucose solution has an 

 advantage over the saccharose. 



In order to obviate this condition, equimolecular solutions of glucose, 



