Climatic changes along with other environmental factors affect many plant physiological processes including synthesis and release into the environment of biologically active metabolites referred to as allelochemicals. The latter, in turn, could affect the ability of plant-acceptors to adapt to abiotic stress factors. Today drought is recognized to be the most challenging abiotic stress causing annual yield losses worldwide about 17%. It is expected that further warming will lead to a sharp increase in the deficit of water in many regions of the world.
The present study focused on the interaction between pre-sowing seed priming with the synthetic analogs of allelochemicals and soil drought on wheat physiological performance and allelopathic potential. The mixture of cinnamic, salicylic and ascorbic acids (0.01, 0.1 and 1 mM) was used as a priming agent. The soil moisture was regulated by watering pots to 20%, 40% and 60% of field capacity. The macronutrient content in the rhizosphere soil was also measured.
The results of our studies indicated complex interactions between allelopathy and soil drought on physiological and allelopathic characteristics of the target plants. Mild allelopathic stress applied to seeds made seedlings more resistant to subsequent drought stress and contributed to the increase of their allelopathic potential. Intensification of drought stress resulted in the decrease of production of allelopathic inhibitors in the tissues of wheat seedlings and enhancement of concentrations allelopathic stimulants and organic carbon in the rhizosphere soil. Changes in allelopathic activity of the rhizosphere soil closely correlated with the changes in organic carbon, nitrates, iron and phosphorus. While soil reaction, concentration of ammonia, manganese, potassium, sulfur displayed no correlation with soil allelopathic activity. The phenomena of cross-synergism and cross-antagonism between the interacting stress factors have been discussed. The observed ability of wheat seedlings to modify allelopathic and nutritional regime in the soil surrounding their roots in response to pre-sowing seed priming and drought stress suggested that plant organisms could directly influence the magnitude of effects of the stress factors through feedback regulation.