## 5 Conclusions  
It is clear that water deficit is a significant stress that reduces plant yield and is associated with a reduction of photosynthesis, and consequently, of plant development. Therefore, water deficiency can have a significant effect on a plant's whole metabolism; secondary metabolite synthesis is also altered. A better understanding of the adaptive strategy of plants grown under water stress is important from an economic and ecological perspective, particularly concerning aromatic plant production. In the current investigation, it was shown that there was an increase in the production of EOs in inoculated or uninoculated peppermint, under drought stress. The results from the present study, taken together with those from a previous investigation [14] have opened up important possibilities for  
Figure 6: Schematic plant responses involved in _Mentha piperita_ subjected to drought stress and treated with PGPR. Under these conditions, a rise in endogenous phytohormone levels (SA, JA, ABA) was observed as well as an increment in EO yield and PT density compared to regularly watered plants. In contrast, VOC emissions were reduced. EO: Essential Oil, VOC: Volatile Organic Compounds, PT: Peltate Trichome; JA: Jasmonic Acid; SA: Salicylic Acid and ABA: Abscisic acid; PGPR: plant growth promoting rhizobacteria.  
improving aromatic plant productivity, particularly in the case of peppermint. The results confirm the importance of the concept of handling drought stress with the intention of enhancing aromatic plant productive capacity by the inoculation with beneficial rhizobacteria. When the purpose of the crops is to obtain _M. piperita_ plants with a high yield of secondary metabolites, EOs and phenolic compounds, we can suggest appropriate inoculation with strains WCS417r or GB03 and the generation of moderate drought stress. Yet, if the objective is greater biomass production, inoculation with PGPR is highly recommended with regular irrigation and avoiding cultivation under drought stress. However, it is crucial to carry out field trials with a rigorous and controlled design, before considering the induction of water deficit in the crop of peppermint plants inoculated with PGPR micro-organisms.  
Conceptualization, E.B.; methodology, L.d.R.C., T.B.P., J.C. and E.B.; validation, J.C. and E.B.; formal analysis, E.B.; investigation, J.C., L.d.R.C. and T.B.P.; resources, W.G. and E.B.; data curation, J.C.; writing--original draft preparation, J.C.; writing--review and editing, E.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by SECRETARIA DE CIENCIA Y TECNICA DE LA UNIVERSIDAD NACIONAL DE RIO CUARTO Grant Number PPI 2020-2022: C529-1, CONSEJO NACIONAL DE INVESTIGACIONES CIENTIFICAS Y TECNICAS (CONICET), AGENCIA NACIONAL DE PROMCION CIENTIFICA Y TECNOLOGICA (ANPCYT) And ALEXANDER VON HUM-BOLDT FOUNDATION.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
This research was supported by grants from the Secretaria de Ciencia y Tecnica de la Universidad Nacional de Rio Cuarto, Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Agencia Nacional de Promocion Cientifica y Tecnologica (ANPCyT) and Alexander von Humboldt Foundation. EB, LC and WG are Career Members of CONICET. JC and TP have fellowships from CONICET. The authors are grateful to [PERSON], a native English speaker, for editorial assistance.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.