polymer (1 g L1), but these enzymatic reductions were less
remarkable than in the former method of application (Fig. 2C).
Only the polymer CH-36 (0.1 g L1) induced b-1,3-glucanase activity
relative to the control.
When determining PAL enzymatic activity, the highest increases
in activity after foliar spray treatments were found with
the two highest concentrations (1 and 2.5 g L1) of the more acetylated
polymer (CH-36), more than three times above the control
level (Fig. 3A). With this polymer, the enzymatic activity increased
with the concentration of chitosan tested, whereas the less acetylated
(CH-12) induced activity above the control level only with
the highest concentration tested. No enzymatic activity was detected
in tobacco leaves when treatments were applied as soil
drench to the rhizosphere except for the polymers when applied
at the lowest concentration (0.1 g L1), which induced about three
times the control level of enzymatic activity (Fig. 3B). The addition
of treatments at seeding caused very large increases in PAL activity
in almost all of the chitosan treatments tested (Fig. 3C). The highest
enzymatic levels were detected with the chitosan polymers at
1 g L1, which induced more than 20 times the enzymatic activity
found in the control.
The peroxidase activity in tobacco leaves treated with foliar
spray increased with most of the chitosan treatments. The most
dramatic changes were detected with the less acetylated polymer
at 1 and 2.5 g L1, the former inducing more than 10 times the
enzymatic activity found in the control (Fig. 4A). Oligochitosans induced
similar, moderate levels of enzymatic activity with all concentrations
tested, whereas the more acetylated polymer induced
activity above control only at the highest concentration tested
(2.5 g L1). This treatment was also the only treatment that induced
peroxidase activity when chitosan compounds were applied
as soil drench to the plant rhizosphere (Fig. 4B). No differences in
enzymatic activity between chitosan and control treatments were
detected when they were applied at seeding (Fig. 4C).