[Studi "priming" callose accumulation in Allium cepa when processing biotic inducers].

Effect of salicylic and caproic acids as an inducters of plant resistance was studied using three onion cultivars differed in resistance to Botrytis spp. Salicylic and caproic acids were shown to prime callose accumulation in Allium cepa varieties resistant to B. allii and B. cinerea. The results obtained sugest that protection of onion against necrotrophs involves the priming of callose accumulation which is important mechanical barrier against invading pathogens.

[Reactive oxygen species and plant immunity].

Reactive oxygen species (ROS) play a key role in plant defense mechanisms. They exert direct antimicrobial action, catalyze the mechanical strengthening of cell walls, function as secondary messengers in the superoxide synthase signal pathway and in triggering the hypersensitive response. Although recent studies have unraveled a nature and the mechanisms of the oxidative burst, many questions related to its mode of regulation, its modulation of signaling networks that control growth, development and defense responses remain unanswered.

[Role of active forms of oxygen in the induction of phytoalexin synthesis in Allium cepa cells]. / Rol' aktivnykh form kysniu v induktsiï syntezu fitoaleksyniv u klitynakh Allium cepa.

The results of studies on the role of plant superoxidesynthase signal system in elicitation of antimicrobial phytoalexin (PA) synthesis in cultured Allium cepa cells are presented. Exogenic application of O2- and H2O2 generators results in formation of PA--Tcibulins 1D and 2 [symbol: see text] in A. cepa cells. The mechanism of PA elicitation does not require peroxidase activity. However, the inhibition of one of the possible sources of the reactive oxygen, HADPH oxidase, suppresses elicitor-stimulated PA production. "Oxidative burst" modulation by different chemical compounds in A. cepa cells results in changes of PA synthesis elicitation. The results obtained suggest the tough correlation between "oxidative burst" and elicitation of defense responses, PA synthesis in particular.

[Effect of UV-B radiation on cytophysiological responses in plants]. / Vplyv UF-B radiatsiï na tsytofiziolohichni reaktsiï u roslyn.

Solar UV-B radiation reaching the Earth's surface is continually increased due to the stratospheric ozone layer depletion. UV-B radiation has been shown to have mutagenic effects damaging DNA, proteins and membranes. During evolution plants developed systems for UV-B perception and effective defense mechanisms. In this review the main UV-B effects, cytophysiological responses of plants and their interactions with microorganisms are analyzed. UV-B-induced signal transduction pathways in plant cells are discussed.