## 5 Conclusions  
Considering the achieved results, it remains to be asked: what are the benefits and harms of treatments of pepper (C. _annuum_ L.), spinach (_S. oleracea_ L.), and lettuce (_L. sativa_ L.) seeds with aqueous extracts of chia (_S. hispanica_ L.), black cumin (_N. sativa_ L.), wormwood herbs (_A. absinthium_ L.), and nettle (_U. dioica_ L.)? According to the results of this study, all the aqueous extracts in all applied concentrations of investigated medicinal plants caused significant decrease in pepper (C. _annuum_ L.) seed germination. Moreover, treatment with 10% aqueous extract of nettle showed a complete inhibition effect on pepper seed germination. The length of hypocotyl and radicle of pepper seedlings developed from sprouted pepper seeds was also smaller in comparison with the control. Chia (_S. hispanica_ L.) 2.5% aqueous extract increased the germination of spinach (_S. oleracea_ L.) seeds, but the differences in hypocotyl and radicle length of seedlings of the same variant of treatment were not significant. The variants treated with 2.5 and 5% aqueous extract of wormwood herbs (_A. absinthium_ L.) and chia (_S. hispanica_ L.) increased the germination of lettuce seeds in the comparison with the control, as well as hypocotyl and radicle length of developed seedlings. The 10% aqueous extract of nettle completely inhibited the germination of lettuce seeds, much like the same phenomenon noted in spinach seed germination tests. Thus, only the treatment of spinach seeds before germination with chia aqueous extract in a concentration of 2.5% stimulated germination of spinach seeds and, wormwood herbs and chia extracts in concentrations of 2.5 and 5% stimulated the germination of lettuce seeds and the growth of hypocotyl and radicle length of developed seedlings. Taking into account the absence and/or insufficient number of studies concerning the allelopathic effect of investigated medicinal plant species aqueous extracts on germination and morphometric traits of pepper, lettuce, and spinach seedlings, the synergistic or antagonistic effects of some phytochemicals are not excluded. Such a topic may be elucidated by future research. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13042258/s1](https://www.mdpi.com/article/10.3390/app13042258/s1)]([https://www.mdpi.com/article/10.3390/app13042258/s1](https://www.mdpi.com/article/10.3390/app13042258/s1)), Table S1: Phytochemical characterization of plant aqueous extracts; Table S2: Germination rates and morphometric characteristics of pepper, spinach and lettuce seedlings. Conceptualization, D.H., R.E. and S.S.; methodology, R.E., D.H. and S.S.; validation, D.H., R.E. and S.S.; formal analysis, M.H. ([PERSON]), Z.Z. and T.J.; investigation, R.E., D.H. and S.S.; resources, M.R. ; data curation, S.S. and Z.Z. ; writing--original draft preparation, S.S.; writing--review and editing, M.H. ([PERSON]), M.R., Z.Z. and S.S.; visualization, M.H. ([PERSON]) and M.R. All authors have read and agreed to the published version of the manuscript. This research was funded by the Krizevici College of Agriculture and by the Croatian Science Foundation, research project entitled as \"Isolation and encapsulation of bioactive molecules of wild and cultivated nettle and fennel and effects on organism physiology\". Project code: HRZZ IP-01-2018-4924. Not applicable. Humans and animals were not involved in this study. Not applicable. The authors used only their own experimental data. **Conflicts of Interest:** The authors declare no conflict of interest and 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. Figure A4: Pepper (_Capsicum anuum_ L.) seedlings; treatments with aqueous extracts of nettle (_Urtica dioxia_ L) in 2.5% concentration (**left**), 5% concentration (**middle**) and 10% concentration (**right**).