T H A T C H E R ON T H E COMPOSITION OF P L A N T S .
801
THE INFLUENCE OF SHADE UPON THE COM- nearly dry in maturing, but is quite apparent in the potato tubers. POSITION OF PLANTS. B y R. W. TWATCAER. Received October 26. 1909.
About two years ago the writer, together with
H. R. Watkins, published a brief note on the “ I n fluence of Shade during Ripening upon the Proximate Constituents of the Wheat Kernel.”’ The experiments there described have been amplified and extended to other crops than cereals. Different densities of shade, different lengths of time of shading, and various different crops have been employed. The same general methods of arranging the shade and of harvesting the crops were used as are recorded in the former paper. The methods of analysis employed were those of the Official Agricultural Chemists. A large number of shaded veysus unshaded samples have been analyzed. Some typical results are included in the accompanying table. Many others might be added, but would serve only to confirm the facts which are probably sufficiently illustrated by those which are presented.
The percentage of mineral matter or “ a s h ” is higher in the shaded samples in every pair except one, the oats. Other pairs of oats than that included in the table showed an increased percentage of ash in the shaded sample, however. Hence the single exception in the table may be regarded as the only exception to the general rule which has been found in our work. The percentage of crude protein is higher in the shaded sample in every case. The average increase is about ro’per cent. of the total found in the unshaded sample but in certain individual cases in the potatoes and the wheat i t rises to nearly 50 per cent. The fat content (ether extract) is generally lower in the shaded samples, but there are occasional exceptions. The differences in either direction are usually small and are probably without very much significance. At least, it will take further experiments, using plants which elaborate larger proportions of ether-soluble matter, to afford conclusive
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Results of analvsis.
Cotuoosition of drv matter. Crop and variety. Potatoes: Burbank Burbank Vigorata Vigorats White elephant; White elephant Field peas: Gov’t. N o 19788 Gov‘t. No. 19788
Kind of shade.
Moisture. Dry matter.
.4sh.
Protein.
Fats.
Fiber.
Starch. Undetermined.
none burlap none burlap none burlap
77.65 78.97 77.02 79.14 78.73 80.72
22.35 21.03 22.98 20.86 21.27 19.28
4.95 5.19 4.14 4.49 4.75 5.09
9.49 11.99 8.99 10.10 9.63 14.25
0.13 0.13 0.38 0.20 0.49 0.56
2.92 2.82 2.99 2.75 3.03 3.10
70.50 65.10 72.70 70.39 67.88 64.83
12.01 14.77 10.80 12.27 14.22 12.26
none burlap
6.87 6.94
93 13 93.06
3.31 3.41
28.52 34.30
1.49 1.12
5.30 4.73
53.83 51.16
7.55 5 28
none 9-02.ducking
9.96 9.28
90.04 90.72
2.63 2.86
19.43 21.82
3.33 1.85
2.72 1.56
66.90 66.13
4.99 5.78
none burlap none burlap
10.19 9.95 8.77 8.70 8.49 8 71
89.81 90.05 91.23 91.30 91.51 91.29
1.94 2.40 2.05 3.22 1.83 2.09
18.94 20.13 .18.17 27.80 18.73 19.92
2.79 2.68 1.74 2.04 2.21 2 06
4.39 3.64 2.85 3 24 2.23 2.60
66.92 66 46 66.78 59.24 68.84 66.85
5.02 2.69 8.41 4.46 6.16 6.48
none burlap
6 96 6.69
93.04 93.31
5.14 4.91
18.00 20.04
4.84 4.03
9.51 9.03
49 72 48.32
12.79 T3.67
none burlap none burlap
8.22 8 10 8.76 9 43
91.78 91.90 91.24 90.57
3.08 3.10 2.43 2.76
19.64 23.67 18.30 20.08
2.57 2.10 2.90 2.62
4.77 4.83 2.30 2.14
62.86 59.25 67.17 65.19
7.08 7.05 6.90 7 21
Emmer: Spring Spring Wheat: Winter Winter Spring Spring Sonora Sonora Oats: Sixty-day Sixty-day Barley: Bearded Bearded Hullless Hullless
none 9-02.ducking
These results show the following effects of the shading : The moisture content is increased or, conversely, the percentage of dry matter is decreased, in the shaded plants. This is not noticeable in those plants which, like the peas and cereals, become very 1
J. A m . Chem. SOC.,29, 764-767 (1907).
evidence as to the effect of shade on this constituent. The acid- and alkali-insoluble matter, conventionally designated as ‘‘ crude fiber,” appears to show no regular effect of the shading, being sometimes slightly higher and sometimes slightly lower in the shaded sample.
So2
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY.
The percentage of starch, as determined by acidhydrolysis, is invariably lower in the shaded sample. But, contrary to our expectations, the effect upon the starch content is less marked than that upon the mineral and nitrogenous matter. I n no case is the proportional decrease in starch equal to the corresponding increase in the other two constituents. The column headed “ undetermined” represents the difference between the total of the five proximate constituents as determined by the official methods and IOO per cent. What this undetermined constituent may be or whether it is simply carbohydrate matter not accurately estimated by the admittedly empirical methods of analysis is a question which many investigators have as yet failed to solve. However, if the last three columns were totaled and reported simply as “ carbohydrates,” the effect of the shading upon this constituent group would be identical with that shown by the starch determinations in every case. I n brief, then, i t may be said that the shading, whatever the texture of the material used or the length of the shading period, caused an increase in the percentage of moisture, mineral matter, and nitrogenous matter, and a decreased percentage of starch or carbohydrates. Rut the increase in other constituents is not directly proportional to the decrease in starch. Hence, we conclude that the changes produced by the shade are not simply a deterrence of the elaboration of starch or carbohydrates in the absence of direct sunlight, but other physiological changes are induced by the shading. This opens an interesting field for study by the plant physiologist. That the attention of other investigators is being attracted to this problem is shown by the recently published results of Lubimenkol and the controversy between Rawson and Ingle and Evans2 as to whether observed changes in composition are actually due to differences in available sunlight or to changes in temperature induced by the shading medium. The thanks of the writer are due to Mr. H . R. Watkins and to Mr. Geo. A. Olson for the analytical work reported in this article. LABORATORY O F THE STATEAGRICULTURAL EXPERIMENT STATION, PULLMAN. WASH. 1 Bull. Acad. St. Petersb., 1907, 395426; and Comfit. rend., 144 (May, 1907), 1060. 2 Tranmaal Agr, Jour., 4 (1906);75,558-566; 16, 743-754; and 17,
140-148.
Dec., 1909
POTASSIUM-IODIDE-STARCH PAPER. B y C. G . STORM.
Received September 2 0 , 1909.
The facts which are noted in the literature of explosives concerning the potassium-iodide- starch paper used in the heat test or Abel test, are found to be misleading in many cases, particularly as to its keeping qualities and the effect of light on the paper. The following work on this subject was carried out by the author while in charge of the chemical laboratory of the Navy Smokeless Powder Works, a t Indian Head, >Id. Heat test paper prepared in this laboratory with proper precautions and preserved in tight stoppered dark bottles has been found in perfect condition after a period of eight years. The method of preparation is about the same as that usually employed, except that the paper before treating is washed for only a short time in distilled water (dipping for about IO seconds), also the potassium iodide and starch solutions are cooled before mixing. The paper used is Schleicher and Schiill’s 597. This quality of paper weighs about j grams per IOO sq. in. I t is cut in strips about 24” x 6”, and after washing hung on clean cords over night to dry in a room free from fumes. The best quality of potassium iodide obtainable is recrystallized three times from hot absolute alcohol, then dried and I gram dissolved in 8 oz. distilled water. Corn-starch is well washed by decantation with distilled water, dried a t a low temperature, 3 grams rubbed into a paste with a little cold water and poured into 8 oz. boiling water in a flask. After boiling gently for ten minutes, the starch solution is cooled and mixed with the potassium iodide solution in a glass trough. The washed and dried paper is then a t once dipped in this mixture, immersing each strip for about IO seconds, and hanging one end over a clean cord to dry. The dipping is done in a very dim light and the paper left over night to dry in a perfectly dark room. Every precaution must be taken to insure freedom from contamination in preparing the materials, and absence of laboratory fumes which might cause decomposition. When dry, the paper is cut into pieces about I ” x 318” and preserved in tight glass-stoppered bottles, the edges of the large strips being first trimmed off about 114in., to remove portions which are sometimes very slightly discolored. The finished paper should be of good white color. It has been found
