276 EXPERIMENT STATION RECORD. 



Investigations concerning the metabolism and respiration of 

 potatoes and other germinating plants, 1^^. Ziegenuein {Priu(if<liehH\s 

 Jahrb. iciss. Hot., ;/3, No. J, pp. rjd.'l-aoO; abs. in For.seh. (reb.atjr. Phys., 

 17 {1894), No. 1 and 2, pp. 143-1 id). — Analyses showed that by tlie exclu- 

 sion of oxygen the decompuwition of the albumen of tlie protoplasm 

 takes place with as great rapidity as when exposed to the ordinary 

 atmospheric conditions. The free nitrogen in the objects of experimen- 

 tation was not exhausted even after subjecting portions of the plants 

 to an atmosphere of hydrogen for L'4 honrs. The effect of light condi- 

 tions on the metabolism and respiration of i)otato tubers was investi- 

 gated at considerable length. The ordinary well-known conditions of 

 sprouts grown in the light and in darkness is mentioned, and C. Kraus 

 is quoted as advocating the theory that the limited growtli in darkness 

 of the first sprouts is (Uie not to lack of light, but to an insufficient water 

 supply. The author thinks it due wholly to the absence of light. In a 

 moist atmosphere the dry matter content of the germinating tuber will 

 be practically the same in tlie light or dark. In a dry atmosphere there 

 will usually be more water found in the potato growing in the dark and 

 a greater amount of starch in the S])routs. 



Potatoes which hasc been growing in the light for a considerable 

 time- in either a dry or a moist atmosphere give oft' considerably more 

 carbon dioxid when placed in the dark. It is probable that lightinduces 

 some conditions more favorable to increased respiration than darkness. 

 In this case the increase is explained as caused by the dissociation of 

 the albuminoid molecules, due to the direct action of the light. The 

 water and sugar content seem to vary according as the tubers are grown 

 in the light or dark. The tuber sprouted in a moist atmosphere and 

 kept in the dark contains more sugar than a similar one in th«i light. 

 The diastase content does not vary in the same way, since there is prac- 

 tically no difference in the ferments present in each case. In a moist 

 atmosphere light causes an increased respiration and consequently 

 greater albuminoid metabolism. Tiie total sugar content goes to regen- 

 erating the destroyed albuminoids, and whatever surplus remains is 

 stored up as reserve material. 



In investigating the relation of temperature to respiration it was 

 found that for the normal respiration of the flower heads of Taraxdcum, 

 as well as of plantlets of wheat, lupines, and the flowers of syringa, the 

 optiuuim temperature is about 40° C. For the sprouts of Abies excelsa 

 and young plants of Vieia faba it Avas 35o^ and for potatoes about 45°. 

 The maximum for the young plants of Avheat, lupine, and bean, the 

 flower heads of Taraxacnm, awd sprouts of Abies is 4005 for .syringa 

 flowers 50°, and for the potato 55°. On the other hand, young wheat 

 and lupine plants continue to respire at as low a temperature as — 2° G. 



If plants of T7t'/« or lupine, having established their respiration at 

 If) to 20°, be warmed up to 30° and again reduced as before, no differ- 

 ence will be noticed in their total respiration. If, however, the temper 



