A micropropagation protocol was developed which may assist in the safeguarding and augmentation of dwindling natural populations of Clinopodium odorum (Griseb.) Harley, a critically and endangered medicinal plant. Factors affecting culture initiation bud sprouting and growth, rooting, and acclimatization were studied, using nodal segments of in vitro germinated seedling as primary explants on six media supplemented with different concentrations and combinations of 6-benzylaminopurine (BAP) (0.5–1.5 and 2-Naphthalene acetic acid (NAA) (0.5–1.5). Best results for culture initiation with sustainable multiplication rates (100%) were obtained on WP medium without any growth regulator. WP with the addition of 0.5？:？1 or 0.5？:？1.5) of BAP and NAA promoted a higher elongation; however, the optimum number of nodes were obtained in plantlets grown on 1/2 MS with the addition of 1？:？1.5 of BAP and NAA. Culture of sectioned individual nodes transferred to the media with different rates of BAP and NAA 1/2 MS-9 (1.5？:？1.5), SH-8 (1.5？:？1.0), and 1/2 B5-4 (1.0？:？0.5) media resulted in no proliferated shoots. The in vitro plants were successfully acclimatized garden soil and sand (2？:？1) in the greenhouse, with over 90% survival rate. The in vitro-grown plants could be transferred to ex vitro conditions and the efficacy in supporting ex vitro growth was assessed, with a view to develope longer-term strategies for the transfer and reintroduction into natural habitats. 1. Introduction Clinopodium odorum (Griseb.) Harley is a small deciduous shrub of the family Lamiaceae commonly known as mu？a-mu？a. In Argentine, the species is restricted to a very specific niche; plant exploration studies in the region has revealed the occurrence of only small populations that is especially characteristic of Pampa de Achala (Córdoba) distributed at an elevation of 1200？m [1]. The fresh herb is used as a flavoring agent for aliments and an infusion of the aerial parts is utilized as an anticatarrhal, antispasmodic, stringent, carminative, digestive, diuretic, laxative, stomachic, soporific, vermifuge, menstrual suppression, flatulent, colic, and tonic digestive and antispasmodic and to help in parturition [2, 3]. This plant species have been excessively collected from its habitats and become endangered due to different contributory factors: extensive denudation of the forest floor, caused by cattle grazing and collection of leaf litter, and removal from the wilderness which is highly used in the preparation of liquor companies “Amargos serranos” [4, 5]. Seed is only the means of
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