Mar. 8 1 9 24 Carbohydrate Variations in Corn and Sorghum Leaves $05 
The maximum increase in the dry matter of the leaves of corn and milo 
was always greater than the increase of the carbohydrates as determined 
by the methods used in these experiments. The case of Dwarf Yellow 
milo in the experiment of July 25, 1917, will serve as a concrete example 
of the above statement. On that date at 6 a. m. the dry matter in a 
square meter of leaf amounted to 45.3 gm. This increased gradually 
during the day until a maximum was reached at 6 p. m., when the dry 
matter amounted to 55.4 gm. per square meter of leaf. Thus each square 
meter of leaf increased in dry weight 10.1 gm. during the 12-hour period. 
The increase in sugars and insoluble carbohydrates from 6 a. m. to 6 p. m. 
amounted to 0.27 and 4.88 gm. per square meter of leaf, respectively, so 
that the total increase in dry weight in each square meter of leaf due to 
the carbohydrates amounted to 5.15 gm. There was thus an increase of 
4.95 gm. of dry matter in each square meter of leaf that could not be 
accounted for by the increase of carbohydrates. In the several experi¬ 
ments the increase of dry matter during the day that could not be ac¬ 
counted for by the increase in sugar and insoluble carbohydrates during 
the same period varied from 7.4 to 53.7 per cent of the total increase of 
dry matter. Detailed information on this point can be obtained by 
consulting Tables VI, VII, and VIII. The undetermined material is. 
evidently not protein, since uupublished data show that in the cases in 
question there is no increase in the absolute amount of nitrogen in the 
leaves during the day. The method used in obtaining the dry weight of 
a unit of area of leaf does not seem to be at fault, since the dry weight 
of a unit of area in all the experiments was approximately the same at 
the close of a 24-hour period as it was at Idle beginning. Since the 
samples used in determining the weight of a unit of leaf area at the begin¬ 
ning and at the close of an experiment were selected from rather widely 
separated portions of the leaf, it would seem that the structure of the 
leaf was uniform and that no appreciable error would be due to variations 
in the leaf samples that were used to determine the absolute amount of 
dry matter. The discrepancy observed between the total increase in dry 
matter in the leaves during the day and the increase in carbohydrates is 
due apparently to the fact that certain temporary storage products in 
the leaves are not detected by the methods used in determining the 
carbohydrates. 
the reducing and nonreducing sugars 
The nonreducing sugars in the leaves of the plants studied were, with 
the exception of the experiment with Dwarf milo and Red Amber sorgo, 
always in excess of the reducing sugars. The increase in the amount of 
the nonreducing sugars and the maximum point of increase of the total 
sugars is also the maximum point of increase of the nonreducing sugars. 
In the three comparative experiments with Pride of Saline com and 
Dwarf Yellow milo the maximum increase in the nonreducing sugars in 
the leaves during the day amounted to 1.54, 2.13, and 1.96 gm. per square 
meter of leaf for the com and 2.52, 2.01, and 2.75 gm. for the same leaf 
area in the case of the milo. In the same three experiments the maximum 
increase in the reducing sugars amounted to only 0.20, 0.37, and 0.18 gm. 
per square meter of leaf in the case of the com and 0.12, 0.70, and 0.00 
gm. for a like area of leaf in the case of the milo. In the experiment with 
milo on August 3, 1917, and with com'on July 3 and 4, 1919, the maximum 
increase in the reducing sugars in the leaves during the day was respec- 
83798—24-7 
