3. Results
3.1. Accumulation of proteins and enzymatic activities induced in
leaves of tobacco plants
Foliar spray of the chitosan compounds tested caused increases
in soluble proteins in tobacco leaves with all chitosan treatments
relative to the control (Fig. 1A). The highest levels of proteins were
detected with the two highest concentrations of the less acetylated
polymer (CH-12), which doubled the amount of protein compared
to control levels. When chitosan derivatives were applied as
drench to the rhizosphere of tobacco plants, all treatments, except
the CH-36 chitosan polymer at 2.5 g L1, increased protein levels
above the control (Fig. 1B). The largest increases were obtained
with the two highest concentrations of CH-12 and the lowest concentration
of CH-36, which accumulated more than twice the protein
level of the control. The oligochitosans induced a similar
change with all three concentrations tested. However, only three
chitosan treatments caused protein levels to increase above the
control levels in tobacco leaves when the treatments were applied
to the soil at seed plantation; these protein levels were about 20%
above the control level (Fig. 1C).
Chitosan treatments applied by foliar spray to the plants caused
increases in b-1,3-glucanase activity relative to the control. Oligochitosans
induced higher enzymatic levels than controls with all
the three concentrations tested, with the two lowest concentrations
(0.1 and 1 g L1) inducing the most change, whereas polymers
only provoked increases in enzymatic activity above the
control at 1 g L1 (Fig. 2A). The addition of treatments as drench
to plant rhizosphere induced enzymatic activity above the control
only with the CH-36 (0.1 and 2.5 g L1) and the CH-12 (0.1 g L1)
polymers. The highest concentrations of the less acetylated polymer
(CH-12) caused decreases in enzymatic activity to below control
levels (Fig. 2B). The addition of treatments at seed planting
caused a decrease in enzymatic activity to below control levels
with all the three oligochitosan treatments and with CH-36