The involvement of low-molecular antioxidants in cross-adaptation of medicine plants to successive action of UV-B radiation and salinity

Artemisia (Artemisia lercheana Web.), common basil (Ocimum basilicum L.), and black cumin (Nigella sativa L.) plants grown in water culture until the stage of 4-5 true leaves were subjected to 10-min UV-B irradiation, treated with 100 mM NaCl, or subjected to the successive action of both stressors. The contents of proline, anthocyanins, flavonoids, soluble phenols, and carotenois were measured. Superoxide dismutase activity was also assayed. Experimental plants could tolerate UV-B irradiation due to the accumulation of phenolic compounds (anthocyanins, soluble phenols, and flavonoids). Anthocyanins contributed mostly in the defnse effect; their content in black cumin and common basil increased 3-5-fold after irradiation. Dynamics of the anthocyanin content in tested plants of all treatments indicates the activation of their biosynthesis by UV-B irradiation and suppression by salinity. Successive action of stressors resulted in synergism of their effects on accumulation of low-molecular compounds in artemisia and common cumin plants. When these plants were irradiated with UV-B and then treated with NaCl, they accumulated more low-molecular compounds than after separate treatment with these stressors, especially in Artemisia. Plant pretreatment with UV-B reduced the adverse action of salinity; this was manifested in the turgor maintenance in salt-treated plants after preliminary irradiation. For basil, salinity was the stronger stressor than UV-B, which was manifested in a decrease in the content of low-molecular compounds. © 2012 Pleiades Publishing, Ltd