Thymus vulgaris L. is a well-know medicinal and aromatic plant native to the Mediterranean region. The essential oil is considered as the main active constituent, being responsible for its typical odour and taste as well as for several therapeutic effects. Our aim was to demonstrate the most important factors influencing the quality and quantity parameters of thyme oil by summarizing the available literature data and our own scientific results. Genetic background, climatic and growing conditions, techniques of primary processing, storage conditions as well as different extraction methods have proven effects on the essential oil properties and, as a consequence, on its biological activity, either.

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. 'Soroksár'). 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.

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The aim of the experiment was to investigate the effect of the level and timing of watering on the productivity and chemical constituents of garden thyme (Thymus vulgaris L., cultivar 'Varico 3') at growth stage (GS) 202 based on the extended BBCH scale in growth chamber for 13 weeks. Different irrigation regimes have been applied based on the soil water content (SWC%) as follows: 1) control (C: 1-13th weeks -70% SWC), 2) mild drought stress (S1: 1-4th weeks -70% SWC, from the 6th week, continuously decreasing drought stress to 40% DVD for 10-13th weeks), 3) sudden drought stress (S2: 1-9th weeks -70% SWC, 10-13th weeks -40% DVD), and 4) constant drought stress (S3: 1-4th weeks -70% DVK, 5-13th weeks -40% SWC). At the end of the experiment, it was determined that water deficiency induced no direct impact on the width and height of garden thyme plants, while internode and shoot lengths were affected significantly. The plants grown under constant drought stress (S3) conditions showed the minimum values concerning lengths (internode 1.30 cm, shoot 7.12 cm), while the highest ones (internode 2.50 cm, shoot 22.08 cm) were found in the control treatment. However, water supply had no significant effect on the shoot number and chlorophyll content of the leaves. The impact of drought stress both on rosmarinic acid and total phenolic content (TPC) was significant and showed the highest values in the S2 and S3 treatments: S2 had the highest rosmarinic acid concentration of 4.61%, and S3 had the highest total phenolic concentration of 0.75 mg GAE ml -1 . A similar result was found for antioxidant capacity in the S3 treatment, where plants reached the highest values (275.44 mg AAE g -1 dry weight), while the total flavonoid content was not significantly affected by different water supply levels. The results show that not only the level of water deficiency but also the change in water supply and the timing of the drought may have a significant effect on the quantity and quality of garden thyme production.

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