Investigation of some morphological and physiological responses of Moldavian balm (Dracocephalum moldavica L.) to selenium under salinity

Salt stress is one of the most important environmental threats that adversely affects the growth, development, and productivity of plants; therefore, suitable approaches are needed to mitigate its negative effects on plants. For this purpose, a pot experiment was carried out in a completely randomized design with two treatments include salinity (0, 25, 50, and 75 mM) and foliar application of selenium (0, 5 and 10 µM Na2SeO4), and the possible role of selenium in regulating Moldavian balm salt tolerance was investigated. Foliar applications of selenium were applied after seedlings establishment at three stages, simultaneously with the application of salinity stress, and then at weekly intervals. Results indicated that growth indices, photosynthetic pigments, and relative water content of leaves in Moldavian balm plants were decreased significantly by various levels of salinity stress. Foliar application of selenium especially at the low concentration increased all the mentioned traits in stress conditions. In contrast, high level of selenium magnified the negative effect of salinity, so that the highest value of malondialdehyde, electrolyte leakage, and water potential were obtained by 10 µM selenium under 75 mM NaCl and caused the accumulation of proline and soluble sugars. This study indicates that selenium at low concentration plays a significant role in alleviating the harmful effects of salinity through photosynthetic pigments, maintaining membrane integrity, reducing water potential, accumulation of compatible solutes, and consequently, improved the performance in Moldavian balm plants growing under salt stress.