Abstract

The two target cactus species in this study, Micranthocereus flaviflorus subsp. densiflorus (Buining and Brederoo) P.J.Braun and Esteves and Micranthocereus. polyanthus subsp. alvinii M. Machado and Hofacker, are endemic to the state of Bahia and have ornamental value. Therefore, this work proposed to establish M. flaviflorus in vitro, as well as to micropropagate both species. The temperature regimes 25°C and 30°C and the alternating temperatures of 15 to 25°C were tested for in vitro germination of M. flaviflorus seeds, which achieved higher germination rates at 25°C. Regarding nutrient media, the lower water potentials of MS and MS/2 media, when compared to agar, allowed the germination of M. flaviflorus seeds. Furthermore, the test of plant growth regulators for in vitro multiplication consisted of regulator concentrations in a factorial arrangement (2x4): Naphthaleneacetic acid (NAA) (0 and 1.34 μmol L^-1) and Kinetin (KIN) (0, 6.74, 20.22 and 40.44 μmol L^-1) in MS/2 media. Shoots of different lengths derived from in vitro propagation were removed from explants and directly planted in plastic cups for survival appraisal. In the in vitro propagation of the studied species, the association of the highest KIN concentration (40.44 μmol L^-1) to 1.34 μmol L^-1 of NAA significantly reduced the number of shoots per explant. The use of 1.34 μmol L^-1 of NAA without cytokinin is suggested for in vitro multiplication in both species. Shoot size was determinant for survival during acclimatization, and so, the usage of shoots at least 0.6 and 1.5 cm long for M. flaviflorus and M. polyanthus, respectively, is recommended for ex vitro establishment.

Key words: Acclimatization, Brazilian flora, Cactaceae, conservation.