Synergistic effect of drought stress and glycine amino acid treatment on structural and antioxidant reactions of Moldavian balm (Dracocephalum moldavica)

Drought is one of the most important abiotic stresses and factors limiting the successful production of plant products worldwide and has adverse effects on plant growth and other metabolic processes. The Moldavian balm (Dracocephalum moldavica) is an annual herbaceous plant. Glycine amino acid is the smallest and the simplest structure in cells and is a soluble, polar, hydrophilic nitrogen compound that accumulates under stress in plants. The purpose of this study was to investigate the effect of glycine amino acid on structural and antioxidant parameters in increasing Moldavian balm drought tolerance.

This study was conducted a factorial experiment based on a completely randomized design with 3 replications in the spring of 2019 in Yazd province. Experimental factors were a: drought stress at 3 levels (100, 70, and 30% of field capacity) and b: foliar application of glycine at 3 levels (0, 2.5, and 5 per thousand). In this study, parameters such as stem length, root length, root/shoot length ratio, root and shoot dry weight, as well as a carotenoid, electrolyte leakage, anthocyanin and flavonoid levels, were measured.

The results showed that the drought stress decreased the shoot length by 23.63% and 33.62% and increase root/shoot length ratio by 46.66% and 53.33%, at 70 and 30% of Fc, respectively. Glycine amino acid increase shoot length and reduced root/shoot length ratio and the highest shoot length (25.44 cm) and root/ shoot ratio (0.30) were obtained with distilled water spraying. Due to the interaction effect of drought stress and glycine, the highest root length (5.50 cm) was obtained in 30% Fc and foliar application with the distilled water. The highest shoot dry weight (0.16 g/plant) was observed in 100% Fc and 2.5/1000 (2.5 g/l) glycine treatments and the highest root dry weight (0.02 g/plant) was in 100% Fc and 5/1000 glycine spraying. Based on comparisons of the mean effects of dual interaction, the highest electrolyte leakage (92.92%) was observed in 30% Fc and the foliar application of glycine amino acid with a concentration of 5 per thousand. The highest amount of carotenoids (11.56 mg/g F.W) was obtained in the treatments of 100% Fc and the foliar application with distilled water and the highest amount of anthocyanin (0.21 absorption/g F.W) in the interaction of 30% Fc and the foliar application of glycine at 2.5/1000, which had no significant difference with a concentration of 5/1000 and finally, the highest flavonoid content (2.16 absorption/g F.W) was observed in interaction with 30% Fc and the foliar application of glycine at 2.5/1000.

Drought stress had the structural reactions such as decrease the stem length and increase the root/shoot ratio and the foliar application of glycine increase the shoot length as well as decrease the root/shoot ratio and inetraction effects on drought stress and the foliar application of glycine increase shoot and root dry weight. Also, the interaction effect of drought stress and foliar application of glycine increased electrolyte leakage, anthocyanin, and flavonoids levels. Application of glycine amino acid at the concentration of 2.5/1000 (2.5g/l), Increase of tolerant plants to drought stress with the most effective role in increasing structural reaction-dependent parameters such as the stem dry weight, root/ stem length ratio as well as antioxidant parameters such as anthocyanin and flavonoid levels.