Agronomy, Melaleuca alternifolia|

Melaleuca alternifolia, known as tea tree, is an Australian medicinal plant widely used in the cosmetic and pharmaceutical industries due to its antibacterial and antifungal properties. Propagation of Melaleuca is limited due to low rates of seed germination and multiplication and the poor rooting of stem cuttings. Thus, micropropagation can be an alternative to the propagation of this woody medicinal species. In this study, different concentrations of 6-benzyladenine (BA) (0, 0.55, 1.11 and 2.22 µM) were tested during the in vitro multiplication phase. It was observed that even the lowest concentration of BA (0.55 µM) could drastically increase the multiplication rate in Melaleuca, compared to the BA-free treatment, due to multiple shoot proliferation. At the rooting stage, in the culture medium without phyto-regulators, individual shoots previously treated with BA had a higher rooting percentage (91–97%) and considerable height growth compared to those of the control treatment (without BA) (66%). However, none of the in vitro plantlets survived to acclimatization stage due to excessive and rapid dehydration of the plantlets under ex vitro conditions, making it the most challenging phase for the micropropagation of Melaleuca. Therefore, a second experimental setup was designed, which included treatments with sucrose, sucrose + sorbitol and sucrose + mannitol in the culture medium at − 0.2170, − 0.3255 and − 0.4340 MPa, respectively, to determine the effects of these osmotic agents on the development of Melaleuca in rooting and acclimatization stages. Sorbitol with sucrose at Ψπ =  − 0.4340 decreased stomatal density in leaves and reduced dehydration of plantlets under ex vitro conditions, but was not enough to provide successful plantlets acclimatization.

Iiyama, C. M. and J. C. Cardoso (2021). “Micropropagation of Melaleuca alternifolia by shoot proliferation from apical segments.” Trees: 1-13.

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