Influence of water supply and fluctuations on yield and quality of lemon balm (Melissa offici-nalis L.)

Abstract

The response of lemon balm (Melissa officinalis) on drought stress was investigated in a pot experiment in 2015-16. In treatment S1, plants grew in 40% saturation of soil water capacity (SWC) for six weeks. In treatment S2, the same level of water supply was used for three weeks, while the control plants received irrigation up to 70% SWC throughout the experimental period. In the second year, after the stress period, a 3 week re-hydration phase was also carried out. Growth, morphology, biomass, active components and antioxidant capacity of the plants were measured. Six weeks growth at reduced soil water content (40% soil water capacity) resulted in a significant decrease of all morphological features of lemon balm as well as the fresh mass of shoots, as compared to the control (70% SWC). The effect of the shorter drought treatment (3 weeks) was less characteristic. After the three week recovery period no significant difference concerning number of branches, leaf length and fresh shoot mass was detectable among the plants. Thus, the retarding effect of even the 6 week drought stress (S1) was reversible in lemon balm. The changes in active components (volatile compounds, phenolics, rosmarinic acid) and antioxidant capacity did not show meaningful changes due to the treatments. After a three-week re-hydration period a significant increase was found in each parameter. It was established that a six week period of water shortage (water content of 40% SWC) could threaten the yield of lemon balm, although re-hydration by regular irrigation may induce significant recovery. The impact of water shortage on the quality of the drug was less critical.

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

“…The findings of our study are confirmed by Németh et al [66], who suggested that short-term water shortages (up to three weeks) followed by rehydration does not affect the essential oil yield and only when water deficit is applied for six weeks are the effects on oil yield irreversible. In contrast to our study, Bonacina et al [1] suggested that salinity stress decreased essential oil yield with increasing salinity levels, while it increased the number of detected volatile compounds.…”