Changes in levels of nicotine and polyamines in leaves and rates of le
af senescence in response to flooding treatment by a low-alkaloid line
(LA 5) and normal alkaloid (Speight G-70) tobacco plants were compare
d. Leaves from LA 5 plants contained 12-, 13-, 2- and 6-fold less nico
tine, putrescine, spermidine and spermine, respectively, than those fr
om Speight G-70 at the start of the experiment (7 days after topping).
Flooding treatment resulted in an increase in levels of putrescine in
both LA 5 and Speight G-70 plants. Flooding did not affect the levels
of spermidine and spermine. Leaf senescence of LA 5 and Speight G-70
was promoted by flooding. However, the senescence syndrome in untreate
d leaves of LA 5 was not as pronounced as that of Speight G-70. Neithe
r was the rate of senescence of flood-treated LA 5 leaves faster than
that of flood-treated Speight G-70 leaves. It appears that endogenous
polyamines may not play a significant role in the control of leaf sene
scence or flood-enhanced leaf senescence of tobacco plants.