## 1 Introduction
The properties of plant growth regulators (PGRs) on the micropropagation of several herbs, including peppermint, have been evaluated in the context of their impact on growth and development; they can be used to obtain microseedlings from protoplasts, nodal and apical segments, and leaf discs for the direct or indirect (with proliferation of callus) method of morphogenesis, and the possibility of their use to increase compounds which are attractive for the bioeconomy has also been explored [1; 19; 25; 26]. To optimize the regeneration process from different initial peppermint explants, PGRs such as BA (6-benzylloadeninopurine), BAP(6-benzylloaminopurine), TDZ (thidiauron), KIN (kinetin), ZEA (zeatin) and 2.4D (2,4-dichlorophenoxyoxyacetic acid), NAA (\(\alpha\)-naphthylacetic acid), IAA (indole-3-acetic acid), or IBA (indolyl-3-butyric acid) have mainly been used, which all have different effects on morpho- and organogenesis, playing a major role in many functions [27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37]. Appropriate protocols for protoplast culture were developed by [PERSON] et al. (1993) [27] and then [PERSON] et al. (1998) [38]. In both studies, the B5 medium was used as the basic element, but that used in the first one contained 1 mg/L NAA, 0.4 mg dm\({}^{-3}\) BA, 0.5% sucrose, 0.5 M mannitol, and 0.1% Gelrite. [PERSON] et al. (1998) [38] obtained the best results in the first stage of the division of protoplasts into free genotypes (\"[PERSON] 38\", \"[PERSON] 19\", and \"[PERSON]'s# \(\times\) 2019\") by combining B5 with 1.0 uM 2.4-D, 2.5 uM NAA, and 4.0 uM BA. In the next stage, the addition of 2.3 uM thidiauron allowed for increased bud formation and regeneration of shoots from calli with a frequency of over 50%. The authors noticed differences in regeneration capability depending on the genotype and the path of shoot regeneration. Additionally, liquid medium was more efficient in supporting first protoplast divisions, and the solid medium was clearly more suitable to support subsequent cell divisions leading to the formation of microcalli. Breeding protoplasts was also useful in the case of new hybrids [28; 30]. [PERSON] et al. (1998) [31] described the process of the in vitro organogenesis of peppermint shoots from explants derived from leaf disks. It was observed that the regeneration occurred within 6 weeks of establishing the culture. The best results were obtained when explants were grown on MS medium with the addition of 300 mM mannitol, 2.0 \(\upmu\)M BA, and 2.0 \(\upmu\)M IBA, and, after two weeks, the explants were transferred to a new medium with 0.5 \(\upmu\)M NAA, 9.0 \(\upmu\)M BA, and 0.5 \(\upmu\)M TDZ (thidiauron), which did not contain mannitol. In the case of peppermint, 78% regeneration was obtained, which may indicate the usefulness of this method for genetic transformation with the help of _Agrobacteriumium tumefaciens_. An experiment for green mint (_Mentula spicata_ L.) was performed by [PERSON] et al. (2012) [PERSON] et al. (2012), where the effect of growth regulators on plant development was examined. The concentration of 2.5 mg/L BAP stimulated greater a yield of new shoots (10) and leaves (38) from the embryogenic callus at the morphogenesis stage, and the full regeneration of shoots was shorter, lasting 62 days. Experience has shown that similar results for root growth were achieved with the participation of IAA and NAA (4 mg: \(\upmu\)m\({}^{-3}\)). The combination of NAA 0.1 mg: \(\upmu\)m\({}^{-3}\) and BA 2.0 mg: \(\upmu\)m\({}^{-3}\) was also repeated by [PERSON] et al. (1998) [PERSON] et al. (1998) in studies on the somatic hybridization of mint for step protoplast division, and for the shooting of microcall in combinations of BA (1-2 mg: \(\upmu\)m\({}^{-3}\)) and TDZ (2-3 mg: \(\upmu\)m\({}^{-3}\)). Moreover, a similar set of regulators with NAA (1 mg: \(\upmu\)m\({}^{-3}\)) and BAP (2 mg: \(\upmu\)m\({}^{-3}\)) as the best combination with a positive effect on the regeneration of shoots of peppermint from nodal segments was indicated by [PERSON] et al.