Hydrogen peroxide as a signal mediator at inducing heat resistance in wheat seedlings by putrescine

Polyamines are multifunctional stress metabolites of plants. However, information on the effect of exo­genous polyamines on plant resistance to high temperatures is contradictory, and it remains unclear which signal mediators are involved in the realization of their physiological effects. The possible involvement of hydrogen peroxide as a mediator under the action of exogenous diamine putrescine on the resistance of etiolated wheat seedlings (Triticum aestivum L.) to hyperthermia (10-minute heating at 46°C) and the functioning of antioxidant system was investigated. It was established that the treatment of seedlings with putrescine in 0.25–2.5 mM concentrations caused a significant increase in their heat resistance. In response to the putrescine effect, a transient increase in the H2O2 content occurred in the root cells. This effect was eliminated by treatment of seedlings with a diamine oxidase inhibitor aminoguanidine and an NADPH oxidase inhibitor imidazole. These inhibitors, as well as the scavenger of hydrogen peroxide dimethylthiourea (DMTU), mitigated the effects of increased heat resistance of seedlings and increased activity of superoxide dismutase and catalase caused by putrescine. Under the influence of DMTU and imidazole, but not aminoguanidine, the effect of increasing the activity of guaiacol peroxidase in the roots of seedlings treated with putrescine was eliminated. The conclusion was made about the role of hydrogen peroxide and the possible participation of diamine oxidase and NADPH oxidase in its formation during the implementation of the stress-protective effect of putrescine on wheat seedlings.