Development, chlorophyll content and nutrient accumulation in in vitro shoots of Melaleuca alternifolia under light-wavelengths and benzylaminopurine (BAP)

Abstract In vitro growing of the Melaleuca could contribute to the cloning of superior genotypes. The studies of factors that affect the micropropagation are necessary, especially by the use of recent technologies, such as the use of light-emitting diodes (LEDs). This study aimed at better understanding the effects of wavelengths on the development and physiology of melaleuca cultivated in vitro, as well as the interaction of LEDs with the main cytokinin used in micropropagation, the N6-Benzylaminopurine (BAP). The BAP and wavelengths, as well as the interaction between them, had a strong influence on most of the variables analyzed, altering the in vitro development, chlorophyll concentrations in the plants, as well as changing the different variables analyzed from the culture medium, such as pH, EC, quantities of Ca2+, Mg2+ and P in the culture media and the nutrient accumulation in the shoots. The results demonstrate that the main effects of the addition of BAP in the in vitro cultivation of melaleuca are: the increase in the number of shoots which resulted in greater increase in fresh and dry mass; reduction of height and chlorophyll contents; completely inhibition of adventitious rooting; higher consumption of Mg and lower consumption of Ca and P from the culture media; higher contents of Fe and lower contents of P, S, Mn, Cu and B in the in vitro tissues.