The effect of various substances on the multiplication of tobacco mosaic virus
has been studied in detached tobacco leaves or in disks cut from the leaves.
Most of such work
has been done to find substances that inhibit multiplication,
and there have been few experiments to find conditions under which the
virus
multiplies most extensively, although work with whole plants has demon-
strated that host nutrition and environment both affect virus production. The
experiments described below show that virus production is greater in detached
leaves placed in solutions containing sugar and phosphate than in water, and
that the extent
to which sugar and phosphate affect virus multiplication vanes
with the physiological conditions
of the leaves and depends on whether they
are kept in the light
or dark.