In order to examine whether
polyamines (PAs) modify the functioning of the scavenging system and oxidative stress levels in water-stressed plants, cucumber (Cucumis sativus L.) seedlings were treated with
spermidine (Spd) prior to
dehydration, and stress-evoked changes in
superoxide dismutase (SOD) (EC 1.15.1.1),
catalase (EC 1.11.1.6),
guaiacol peroxidase (EC 1.11.1.7) activities, H(2)O(2) and
superoxide radical levels were determined. Free PA content during Spd treatment and during the stress period were also determined. Exogenous application of Spd differentially influenced
enzymes of the antioxidative system under stress conditions; we observed an increase of
guaiacol peroxidase activity, and, to a lesser degree, a reduction of SOD and
catalase activities in Spd-treated plants in comparison to untreated stressed plants.
Hydrogen peroxide and
superoxide radical contents were also reduced in stressed plants after Spd pretreatment. These positive effects were observed in the case of 1mM Spd concentration. A higher concentration (3mM) influenced negative, more significant stress-induced changes, but a lower concentration (0.1mM) had a very limited effect. In summary, PAs are able to moderate the activities of scavenging system
enzymes and to influence oxidative stress intensity.