CARBOHYDRATE PRODUCTION IN HEALTHY AND IN 

 BLIGHTED SPINACH 



By Rodney H. True, Physiologist in Charge, and Lon A. Hawkins, Physiologist, 

 Plant Physiological and Fermentation Investigations, Bureau of Plant Industry 



Spinach plants affected with the blight show many symptoms pointing 

 to a derangement of functions concerned with the carbohydrates, among 

 which are the yellowish-green color and the sweetish taste. It was there- 

 fore deemed important to investigate these constituents in normal and 

 in diseased plants. The material was taken from commercial fields near 

 the Virginia Truck Experiment Station. The plants were carefully dug 

 with a spade, and the soil adhering to the roots was quickly washed off. 

 To reduce the translocation of products, the plants were divided into 

 roots and tops, and after being loosely packed in market baskets were 

 covered with paper and stored in a building in diffused light. The col- 

 lection took place late in the forenoon on February 5, 1 91 5, a clear day. 



The samples were kept in a cool place while in transit and were taken 

 to the laboratory at 7. 30 the next morning, where they were given imme- 

 diate attention. 



Starch, sucrose, and reducing sugars were determined by the usual 

 methods. The results of these determinations are presented in Table I 

 as percentages calculated on both fresh and dry weights of tops and on 

 the fresh weights of the roots. 



It will be noted that the samples of diseased tops have a somewhat 

 greater percentage of dry matter than the healthy tops. 



The reducing sugars under the conditions here given are clearly less 

 abundant in the tops of blighted plants than in the normal samples, 

 while in the roots but a trace is present in either type of material. The 

 situation with reference to the sucrose in the tops, however, is quite the 

 reverse, the diseased plants containing a considerably greater quantity 

 than those in health. This difference is so great as to give a much higher 

 total sugar content for the pathological material, a fact which in part 

 accounts for the strikingly sweet taste found in the latter plants. It is 

 of interest, however, to note that no noticeable sweetness is found in the 

 normal leaves, although in the material collected in 191 5 they contain 

 nearly 80 per cent as much total sugars and nearly 65 per cent as much 

 sucrose. Since the taste of sweetness is interfered with by a variety of 

 other taste sensations, it is possible that certain substances having a 

 marked taste may be present in the normal material and absent in that 

 affected by the disease. On tasting the fresh material in the field it 

 seemed that the characteristic "spinach" taste so strongly marked in 

 the healthy leaves was almost lacking in the sweet diseased leaves. 



(381) 



