Effect of water deficit on yield and quality of lemon balm (Melissa officinalis L.
The aim of the present study was to investigate the effect of the level and timing of watering on the productivity and chemical constituents of lemon balm (Melissa officinalis L. cv. 'Soroksar' As control 70% soil water capacity was set. In treatments stress1 and stress2 the soil water capacity decreased stepwise from 70% to 30% and sharply from 70% to 30% respectively. In the strongest and permanent water deficit treatment stress3 30% soil water capacity was applied. Among the production parameters the water deficit reduced the plant height, bush diameter, fresh and dry mass of the plants. Besides, the root:shoot ratio increased, while in the root length, fresh and dry mass no significant differences were detected. Water deficit also influenced the phenolic compounds. Under stress1 and stress2 circumstances decreased accumulation of flavonoids (by 14 22% was observed while the drought conditions resulted in enhancement in the rosmarinic acid concentration (1 22% compared to the control) The highest antioxidant capacity (201 mg ascorbic acid equivalent g 1 dry mass) and total phenolic content (178 mg gallic acid equivalent g 1 dry mass) were measured in treatment stress3 where permanent 30% soil water capacity was applied, while the stress2 plants produced the lowest antioxidant capacity (66 mg ascorbic acid equivalent g 1) and total phenolic content (105 mg gallic acid equivalent g 1) The gradually decreasing water supply did not modify antioxidant capacity and total phenolic content. The results show that not only the level of water deficit, but its timing and dynamics may have significant effects on the quantity and quality of lemon balm production.