INFLUENCE OF NITROGEN SUPPLY ON THE RATE OF MULTIPLICATION OF TOBACCO-MOSAIC VIRUS

Abstract

Turkish tobacco plants, grown in sand, were supplied with nutrient solns. containing either a low, medium, or high amt. of N. Assay for virus activity was made on Phaseolus vulgarus var. Early Golden Cluster. The virus protein was isolated by means of an air-driven ultracentrifuge. In young plants a difference in virus activity could be detected by the 5th day after inoculation, when the juice expressed from low-N plants was found to be only about 35% as active as that in juice from plants receiving more N. By the 8th day, it was less than 25% as active. A 3-fold difference was recorded in the virus-protein contents in the juices of these 2 treatments. The activity data calculated per plant indicate that by the 8th day after inoculation the juice from the high-N plants contained 12 times more virus than that from the low-N plants, even though the high-N plants were only 2-3 times as large. From the 4th to the 12th day after inoculation, the virus-protein content of the juice expressed from the low-N plants increased about 20 times, whereas that of juice from the high-N plants increased over 200 times. Older diseased plants receiving the medium-N soln. for longer-periods before being given the high-N soln. attained greater virus activity as a result of the supplementary supply of N. The larger the plant the more time is required for the increased N supply to become effective. The exptl. evidence is interpreted as supporting the view that the increased virus activity associated with an increased N supply is due primarily to an increase in the rate of virus multiplication in the case of the high-N plants and only slightly, if at all, to the partial inactivation of the virus entity in the case of the low-N plants.