With deepening studies on the regulation and coordination of plant growth, development, and their responses to unfavorable environmental factors, the mechanisms of plant metabolism regulation seem more complex [1,2]. A number of plant compounds were found to affect plant growth, development, and tolerance to abiotic and biotic stressors. Among them are auxins, gibberellins, cytokinins, brassinosteroids, abscisic, jasmonic, and salicylic acids, ethylene, peptides, polyamines, oligosaccharides, Ca 2+ , hydrogen peroxide, nitrogen oxide, and others. The investigation of plant biochemical and physiological responses to changed environmental conditions led to elucidation of specific features of these responses and also of some common responses to a combination of several stresses. Both biotic and abiotic stresses induce in plants a chain of events: signal recognition, the formation of second messengers (for example, inositol phosphates), the changes in intracellular ion fluxes, such as Ca 2+ , the accumulation of reactive oxygen species (oxidative stress), phosphorylation of certain proteins, and transcription of the genes required for the synthesis of ABA, ethylene, jasmonate, salicylate, and other compounds [3-6]. These physiologically active compounds determine successive series of metabolic changes that result in the accumulation of metabolites facilitating plant adaptation. A microarray technology revealing changes in the expression of the whole set of plant genes, permits determination of a strict sequence of events occurring in response to an environmental stressor [7-9].In the context of understanding dynamic processes occurring in living organisms in response to external factors, the examination of interrelations between "separate parts" and the manifestation of these interrelations in the responses of the "whole" are of a substantial importance. One of the promising approaches to the solution of this problem is the concept of synergism [10]. Corning [10] believes that synergism is a ubiquitous and important aspect of the Nature related to structural or functional effects resulting from the combination of things, when the effect of the whole differs from the effects of the separate parts, i.e., the whole exceeds the sum total of the components. Thus, synergism is any combined effect at any level of the living systems (from enzymes to ecosystems), including symbiosis and evolutionary changes. In this aspect, the works of Russian scientists A.S. Famintsin [11] and B. KozoPolyanskii [12] performed at the beginning of the last century are of exceptional interest. These scientists compared such organisms as lichens with their constituents, algae and fungi, and demonstrated that this dual organism manifested new properties absent from its components.It is evident that numerous plant secondary metabolites are the products of biological evolution under definite ecological conditions [13][14][15]. A diversity of chemical compounds involved in plant responses implies that they can interact. Simultaneous action of two ...
