Factors affecting the amount of tobacco mosaic virus nucleic acid in phenol treated extracts from tobacco leaves

Extracts from the lower leaves of tobacco plants infected with tobacco mosaic virus and pulped in the presence of phenol are less infective than extracts from leaves pulped and then treated with phenol. Extracts from uninfected leaves mixed with purified virus behave similarly. The difference becomes progressively smaller as leaves are taken from further up the plant. The difference is smaller when the interval between pulping and adding phenol is short, and it is still smaller if air is rigidly excluded during the interval. Fixation of virus nucleic acid to the leaf fibre is the main factor responsible for this difference. Part of the normal nucleic acid of the leaf is fixed similarly. Fixation is partly prevented by including yeast nucleic acid in the extraction fluid, or by excluding Ca2+ from it by adding citrate. Part of the nucleic acid is held tenaciously by the fibre. The possible significance of this fixation in vivo in controlling the apparent susceptibility to infection of plants in different physiological states is discussed.