INFLUENCE OF ILLUMINATION ON REDUC- 

 ING SUGAR CONTENT OF ETIOLATED 

 BARLEY AND OAT SEEDLINGS 



By ROBERT L. WKIXTRAUB' and LKONARD PRICE 

 Division of Radiation and Orf/anisnts. Sinitlisonian Institution 



Increased rate of carbon dioxide production following illumination 

 111' etiolated barley scedling^s was observed by Weintraub and Johnston 

 (i(;44). A possible mechanism for this effect is suggested by the 

 finding of Parija and Saran (1934) of increased reducing sugar con- 

 tent caused by brief illumination of starved Aralia leaves, in conjunc- 

 tion with the numerous reports in the literature of an intimate relation 

 l)etwecn respiratory rate and reducing sugar content of plants. In 

 order to test this possibility experiments have been conducted to ascer- 

 tain whether changes in the reducing sugar content of etiolated cereal 

 seedlings are produced by illumination of relatively short duration. 



"Seeds"- of barley (varieties Hannchen and Sunrise) and of oats 

 (variety Markton) were planted on filter-paper-covered porous stone 

 wicks and allowed to germinate at room temperature in total dark- 

 ness. At suitable ages, seedlings were exposed to the unfiltered radi- 

 ation from a frosted tungsten filament lamp for periods of 60 to 200 

 minutes, at the end of which they were harvested. 



For the sugar analyses, the shoots were severed just above the seeds, 

 cut rapidly into small pieces with scissors, and placed in light-tight 

 aluminum cans for weighing. Unilluminated plants were similarly 

 sampled at the same time, the operations being performed in absence 

 of light. The fresh weights were determined as rapidly as possible 

 and the tissues transferred quickly to boiling 95-percent ethyl alcohol. 

 Tests showed that reducing substances were removed completely 

 after three additional extractions with boiling 80-percent alcohol : 

 tliis procedure was followed throughout. The alcohol was removed 

 from the combined extracts on a water bath and replaced by water. 



Reducing power was estimated with the copper-iodometric reagent 

 rrSO of Shaffer and Somog^i (1933). In some experiments total 



* Now with the Department of the .\rmy, Camp Dctrick, Frederick. Md. 

 2 Kindly supplied by Mcrritt X. Pope and T. Ray Stanton of tlie U. S. 

 Department of Agriculture. 



SMITHSONIAN MISCELLANEOUS COLLECTIONS. VOL. 110, NO. 2 



