On the turbidity of pressed-out juices from some virus-infected plants

Abstract

The present paper deals with the results of experiments on the turbidity, being measured with the electric photometer, of the juices expressed-out from virus-infected tubers of potatoes of sweet potatoes and tuberous roots of radish or turnip. The results obtained are summarized as follows.
During storage the turbidity of the healthy potato juice is generally slightly lower than that of the diseased. The turbidity was shown to be low according to the severity of the disease and also to the lapse of time in storage. The correlation between the turbidity and the tuber size was not recognized. As for the average turbidity tested with many tubers, the healthy juice is geneaally higher than diseased, though individual tuber shows irregular in turbidity. The largest difference between the healthy juice and the diseased was shown at 1/8 dilution.
The turbidity of radish juice gave the similar results to the case of potatoes, and the difference between the healthy and the diseased is more larger. The turbidity of the diseased younger tuberous roots seems to decrease owing to the accumulation of certain substances, though that of the diseased older one, during the later growing period, increases owing to the stagnation of formation and transportation of the substances. The upper part of the root is higher in turbidity than other parts.
The turnip juice gave similar results to the case of radish, and the sweet potatoes showed slight difference in turbidity between the healthy and the diseased.
The turbidity degree of juice from the living materials shows reversely to the protein content, but the older juice or the diseased seldom shows contrary to such a rule because of the occurrence of coaglation or precipitation by the auto-denaturalization. From these experiments it is clear that the turbidity test is not to be utilizable for the purpose of quantitative analysis, though it may be utilizable for diagnosis.