Study of Biofertilizers Effect on Some Physiological and Biochemical Traits of Dracocephalum kotschyi Boiss. Under Different Soil Moisture Regimes

Dracocephalum kotschyi Boiss. is one of the most important medicinal plants of the Lamiaceae family, which is endangered due to unfavorable environmental conditions. in order to evaluate the effectiveness of biofertilizers on changes in some physiological and biochemical traits, the effect of biofertilizers at four levels on Dracocephalum kotschyi growth under drought stress at three levels (irrigation until the completion of 80%, 60 and 40% of field capacity), an experiment was carried out in 2019. The study of changes in photosynthetic pigments, chlorophyll fluorescence and leaf relative water content in D. kotschyi in response to various biofertilizers and different irrigation regimes showed that with increasing drought stress, chlorophyll a, b and total chlorophyll along with chlorophyll fluorescence (Fv/Fm) had a significant decrease. While the use of supernitroplus and biophosphorus biofertilizers in irrigation conditions up to 60 and 40% of field capacity significantly increased the above-mentioned traits in the D. kotschyi leaves in comparison with the plants treated with nitroxin fertilizer and control plants. Increased drought intensity also caused a significant increase in carbohydrates, soluble proteins, anthocyanins and flavonoids, although the use of biofertilizers containing growth-promoting bacteria, further enhanced the amount of these compounds compared to the control. The highest levels of anthocyanins (37.82 mg g-1 fresh weight) and flavonoid compounds (16.62 mg g-1 fresh weight) were found in plants grown under severe drought stress (irrigation up to 40% of field capacity) and Biophosphorus application. Based on the results, the use of biofertilizers supernitroplus and biophosphorus improved the physiological and biochemical properties of D. kotschyi under both drought and non-water stress conditions. The increase in traits indicates a kind of adaptation to drought stress conditions.