Influence of Presowing Irradiation and High Concentrations of Salts on Wheat

Under natural conditions plants usually experience impact of several unfavorable factors. That is why the resistance to the simultaneous exposure to several stressors is of great importance in selection. Moreover, studies have shown that a plant'sresponse to the combined effect of several stressors differs from the response to a single stress exposure (Craufurd and Peacock, 1993; Jiang and Huang, 2001; Pnueli, et al., 2002); e.g. it was established that activation of diverse genes took place in response to different stresses in Arabidobsis the (Mittler et al. 2004). Moreover, literary data prove that between the responses to different stresses synergic or antagonistic relations may exist (Walter, 1989; Sandermann, 2004). More common are data on the simultaneous effects of drought and high temperature stresses on agricultural crops (Craufurd and Peacock, 1993; Jiang and Huang 2001). It has been established that the combined effects of these two stressors have afar more detrimental effect on plant growth and development than the effect of each individually (Jagtap et al., 1998; Wang and Huang, 2004).

Natural ultraviolet (UV) radiation and soil salinization are the stressors that often cause problems for agricultural crops. Soil salinization is one of the most acute environmental problems in today’sagriculture. According to the Food and Agriculture Organization of the United Nations (FAO), more than 20% of the world’ssown area and half of its irrigated land is salinized due to secondary salinization and alkalination and became unsuitable for agriculture. Over the next 25 years, 30% of irrigated land is expected to be salinized, and by 2050 this number will increase to 50% (Gogue, 2014). Georgia is no exception in terms of soil salinization-the total area of saline soils is 1.6% (Urushadze and Blum, 2014). One of the approaches to solve this problem is identification of existing salt resistant species, or breeding of new, resistant forms.

Investigation of the effect of UVirradiation on plants is very popular as well. Band C sections of UVradiation are known to affect negatively plant growth, photosynthesis, and other vital processes, due to the production of active forms of oxygen. It is well known that these forms of oxygen damage cell macromolecules and can even cause its death (Toncheva-Panova et al., 2010; Zu et al., 2010; Schreiner et al., 2012). However, on the other hand, it is established that low doses of UV-B or UV-C may enhance stress adaptive responses in the plant, due to activation of enzymatic and non-enzymatic defense systems (Lavola et al., 2003; Katerova and Todorova, 2011).

To study the effect of UVradiation on plants is interesting from another point of view, as well. In particular, today there is a growing interest in pre-sowing treatment of seeds by physical, environmentally safe methods. Numerous data are available on the positive influence of pre-sowing treatment of seeds with various types of electromagnetic radiation, including UV, on both yield quantity and quality, as well as on plant protection against various diseases (Dubrov, 1963; Ghallab and Omar, 1998; Delibaltova and Ivanova, 2006 Investigation of the effect of high concentrations of salts and pre-sowing treatment with UV on economically important crop-wheat was the aim of the study. It included several aspects: 1. Testing of the salt resistance of experimental wheat species; 2. Investigation of the impact of direct UVirradiation on the growth and development of the studied species; 3. Studying of the effect of seeds pre-sowing irradiation on the salt resistance of plants, developed from these seeds. According to the purpose of the study, the impact of each stress factor on research objects was studied separately and in combination. The results obtained allow judging how pre-sowing irradiation affects the salt resistance of the studied wheat species.