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Two experiments (in Petri dishes and in soil) were conducted to investigate the effects of osmopriming on seed germination and the early seedling characteristics of caraway (Carum carvi L. var. annua). The priming treatments in the Petri dish experiment were: polyethylene glycol (5%, 10% and 20%), KNO3 (0.5%, 1% and 2%) and KCL (1%, 2% and 4%) with three different soaking times (12, 24 and 36 h) along with control (non-primed seeds). Only polyethylene glycol and H2O were applied in the cell tray experiment, which were then compared with the non-primed seeds. In the Petri dish experiment, all three priming reagents significantly enhanced seedling length, with the most effective treatments being 5% PEG, 2% KNO3 and 1% KCL for 12 h. The plumule dry weights were also increased significantly after PEG (20% for 36 h), KNO3 (2% for 24 and 36 h) and KCL (1% for 12 h) treatments in comparison with the control. In the soil experiment, osmopriming with PEG significantly improved the germination rate (GR) and percentage, the plumule dry and fresh weights and the plumule length of caraway seedlings when compared with the control. A 23% higher germination percentage was recorded for the seeds treated with 5% PEG for 24 h as compared with the non-primed seeds. The PEG-primed seeds produced significantly longer seedlings when treated with 5% PEG for 24 h. All of the applied PEG treatments significantly enhanced the plumule fresh and dry weights, with the best outcomes being after 5% PEG (24 h) and 10% PEG (36 h) treatments, respectively. The 12-h hydro-priming also significantly enhanced all of the studied germination parameters when compared to the control. The results of the presented experiments show the significant positive effects of seed priming on caraway germination and how early seedling performance can easily be adopted by producers.

A pot experiment was conducted to assess the effect of drought stress on growth and secondary compound accumulation of Ocimum species, in a semi-controlled greenhouse during the year 2020. The experiment was performed as a factorial that was based on a randomized complete design with three species of basil namely O. basilicum ‘Genovese’, O. x africanum, and O. americanum, and three levels of water supply (70, 50, and 30% soil water capacity-SWC) that were replicated twice. The results revealed that severe drought conditions (30% SWC) significantly lowered the relative water content and, as a consequence, plants were shorter, narrower in the canopy, and produced smaller leaves which, in turn, resulted in a 50% fresh and dry herb yield loss. Furthermore, severe drought stress negatively affected the essential oil content (except O. x africanum where no change was seen), essential oil yield, and the antioxidant capacity. However, slight enhancements of glandular hair density were observed in the drought treatment than in the control. Regardless of the soil water capacity variation, the major compound of the essential oil and total polyphenol content remained unchanged. Besides drought, morphological and chemical variations were also detected among the Ocimum species. Sweet basil cultivar Genovese produced the maximum biomass (344.7 g/plant) whereas O. x africanum accumulated higher essential oil (2.79%). The major compounds that were identified were linalool in O. basilicum; 1, 8-cineole, and camphor in O. x africanum; and O. americanum had more neral and geranial. In conclusion, a higher water supply is recommended for higher biomass and essential oil yield production in the tested basil species.

Summary Introduction: Irrigation plays an important role in the cultivation of medicinal plants. There is a lack of information on intraspecific variability of reactions to the effect of drought. Objective: The aim of the current study was to test the effect of irrigation on four sweet basil (Ocimum basilicum L.) cultivars (‘Genovese’, ‘Kasia’, ‘Keskenylevelű’, ‘Wala’). Methods: In an open field experiment irrigated and non-irrigated treatments were set. Plants were harvested in full flowering stage. Before the harvest, the stomatal conductance and chlorophyll content were measured. The production-related parameters were recorded. In the plant material the glandular hair density, essential oil content and composition (GC-MS) and volatile composition (SPME-GC-MS) were identified. Results: Stomatal conductance of the irrigated plants was 2.5–4.5 times higher than in the non-irrigated ones. The chlorophyll content showed only slight changes. The irrigation had a positive effect on the production. The leaf to stem ratio was not modified by the watering. Irrigation negatively influenced the glandular hair density and the EO content, however it increased the EO yield by 40–129%, depending on the cultivar. Significant compositional changes were registered only in the EO of cultivar ‘Kasia’ for linalool, 1,8-cineole and tau-cadinole ratios. Conclusion: Irrigation increases the biomass and EO yield of basil while the composition of the EO is mostly unchanged. Only slight differences were observed among the cultivars.

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.