SPECIFIC BIOLOGICAL ACTIVITY OF TOBACCO-MOSAIC VIRUS AS INFLUENCED BY AGE OF LESION AND NITROGEN SUPPLY

Abstract

Expts. were carried out to study virus multiplication in the inoculated leaf and the effect of N starvation on virus thus formed. Turkish tobacco plants grown in nutrient sand cultures were inoculated with tobacco-mosaic virus on one of the lower mature leaves of each when the plants were about 6 in. tall. At intervals, virus was isolated by means of an ultracentrifuge and assayed for biological activity. Virus in the inoculated leaf continued to increase both in amt. and in specific biol. activity (activity per unit of wt.) for as long as 20 days after inoculation; withdrawal of the N supply inhibited the increase in specific activity earlier than it did the increase in virus protein. Confirmation of the finding that virus in young lesions displays only a fraction of its potential biological activity was obtained by comparing virus isolated from the inoculated leaf with virus isolated from the more recently invaded top of the plant. Calculations from the rates of sedimentation in the analytical ultracentrifuge indicated that virus preps. from young lesions may contain some particles considerably larger than those characteristic of virus prepns. from older lesions.