Essential Oil Composition and Bioactive Properties of Lemon Balm Aerial Parts as Affected by Cropping System and Irrigation Regime

Abstract

The ongoing climate crisis necessitates the sustainable use of natural resources and the adoption of environmentally friendly agronomic practices. Deficit irrigation is an ecofriendly technique that allows for the improvement in the water use efficiency of crops. On the other hand, medicinal and aromatic crops, which usually have an innate tolerance to harsh conditions, are suitable candidates for cultivation under low-input cropping systems. In the present study, Melissa officinalis plants were cultivated under conventional and organic cropping systems, while in each system two irrigation regimes (full irrigation or deficit irrigation) were tested. The aerial parts of the plants were evaluated in terms of growth and physiological parameters, chemical composition, antioxidant activity, essential oil yield and essential oil composition. Our results indicate that prolonged water stress after two deficit irrigation cycles had detrimental effects on the plant growth and biomass production, whereas it significantly increased the essential oil yield, regardless of the cropping system (organic or conventional cultivation). The recorded physiological parameters are in agreement with morphological features, especially the stomatal conductance, which was significantly reduced under deficit irrigation for both cultivation systems, revealing that the growth inhibition was the result of stomatal closure and carbon dioxide deprivation. Deficit irrigation and organic cultivation also increased total phenol and total flavonoid content, especially in the second harvest, thus resulting in higher antioxidant activity assayed by the FRAP method. In contrast, DPPH and ABTS methods did not show any differences among the tested treatments in the second harvest, which suggests that other bioactive compounds are also involved in the overall antioxidant mechanism of lemon balm plants, as indicated by the increased ascorbic acid content. Regarding the essential oil composition, the major detected compounds were geranial and neral and, although they were both increased under the organic cropping in the first harvest, the same trend was not observed in the second harvest. Finally, a variable effect of cropping system and irrigation regime on minerals content was recorded. In conclusion, deficit irrigation is an ecofriendly practice that could be applied in conventional and organic cropping systems of lemon balm crops, aiming to reduce irrigation water consumption and compensate for reduced herb yields with increased essential oil yield and polyphenol content.

Antioxidant Activity and Photosynthesis Efficiency in Melissa officinalis Subjected to Heavy Metals Stress

“…Lemon balm farming is stimulated by the remarkable low essential oil output, which, on average, is 0.1%, while cultivation yields approximately five metric tons of the dried material per hectare [ 7 ]. The largest world producers are Egypt, Turkey, the United Kingdom, and the United States [ 8 ]. Poland’s production is among the largest in Europe and approaches 1500 tons annually [ 9 ].…”

RNA-seq analysis reveals narrow differential gene expression in MEP and MVA pathways responsible for phytochemical divergence in extreme genotypes of Thymus daenensis Celak

“…Thymus species are exceptional case studies in chemodiversity domains, as over 20 chemotypes have already been described for their EO profiles [ 37 ]. To date, several studies have shown that the phytochemical constituents of plant species can be altered due to agronomic practices [ 38 ], natural diversity [ 39 ], intra- or inter- specific variations [ 4 , 40 ], abiotic stresses [ 41 ], elicitor applications [ 42 ], and site-directed mutagenesis in corresponding enzymes [ 43 ]. In another study, Vaičiulytė & Ložienė stated that even meteorological factors can significantly influence the amounts of phenolic and non-phenolic monoterpenes in three chemotypes of Thymus pulegioides [ 44 ].…”

The Identification of Polyphenolic Compounds and the Determination of Antioxidant Activity in Extracts and Infusions of Peppermint, Lemon Balm and Lavender

“…The difference in dry matter content between peppermint and lemon balm was as much as 13.18 g/100 g. Similar differences between mint and lemon balm are presented by the results of Kaur et al [29]; in this case, the difference was 14.5 g. Similar results of dry matter content for peppermint were achieved in the studies of Uribe et al [30] (27.5%). In turn, Chrysargyris et al [31], on the first date of harvesting lemon balm, provided the DM content in the range of 21.06-24.48% and emphasized that it depended on the method of cultivation and irrigation of the crop. The dry matter content results presented in this study are much higher, which may be related to the plant development phase [24], as well as the use of other varieties and climatic conditions.…”