Application effects of mycorrhiza on physiological traits of flax (Linum usitatissimum L.) under UV stress

Among the different types of mycorrhizas, arbuscular mycorrhiza is the most common peaceful type of symbiosis between the land microorganisms and plants with a great economic and ecological importance. On the other hand, UV irradiation is known to cause oxidative damage to plants by triggering an increased level of production of reactive oxygen species (ROS). The objective of the present investigation was to study the effects of mycorrhiza on physiological traits of flax (Linum usitatissimum L.) under UV stress. The flax plants were grown in two mycorrhizal (M) and non-mycorrhizsal (NM) groups with a diurnal regime of 16 hour light and 8 hour dark at 18-29°C. Mycorrhizal plants were colonized by inoculum obtained from Glomus versiforme and Glomus etunicatum culture. They were divided after 21 days of growth. One set of pots served as the control, and the other set was treated with UV radiation (312nm) for 1 hour each day for 14 days. The study was conducted in a completely randomized design including three mycorrhizal treatments (with G. etunicatum, G.versiforme and without mycorrhiza), and two UV treatments (with UV and non-UV) in three replications. Results showed that chlorophyll a and chlorophyll b content was significantly reduced in treated plants in comparison with the control. This decrease was less obvious in mycorrhizal plants as compared with non-mycorrhizsal samples; however, antioxidant enzymes activity increased when plants were irradiated with UV light. This increase was more dramatic in mycorrhizal plants samples than non-mycorrhizsal ones. In addition, results showed that malondialdehyde content was increased when plants were irradiated with UV light. This increase was more dramatic in non-mycorrhizsal samples than mycorrhizsal ones. According to the obtained results, it is concluded that UV-B stress has serious effects on Shahin-dezh cultivar and mycorrhizal symbiosis with the two fungi species can somewhat reduce this stress. Furthermore, colonization with Glomus versiforme resulted in better ameliorative effects on plants in comparison with Glomus etunicatum.