Incidence of hyperaccumulation and tissue-level distribution of manganese, cobalt, and zinc in the genus Gossia (Myrtaceae)

The rare phenomenon of plant manganese (Mn) hyperaccumulation within the Australian flora has previously been detected in the field, which suggested that the tree genus Gossia (Myrtaceae) might contain new Mn hyperaccumulators. We conducted the first growth experiment on Gossia using a multi-factorial dosing trial to assess Mn, cobalt (Co), and zinc (Zn) (hyper)accumulation patterns in selected Gossia species (G. fragrantissima and G. punctata) after a systematic assessment of elemental profiles on all holdings of the genus Gossia at the Queensland Herbarium using handheld X-ray fluorescence spectroscopy. We then conducted detailed in situ analyses of the elemental distribution of Mn, Co, Zn and other elements at the macro (organ) and micro (cellular) levels with laboratory- and synchrotron-based X-ray fluorescence microscopy (XFM). Gossia pubiflora and Gossia hillii were newly discovered to be Mn hyperaccumulator plants. In the dosing trial, G. fragrantissima accumulated 17 400 µg g-1 Mn, 545 µg g-1 Co, and 13 000 µg g-1 Zn, without signs of toxicity. The laboratory-based XFM revealed distinct patterns of accumulation of Co, Mn, and Zn in G. fragrantissima, while the synchrotron XFM showed their localization in foliar epidermal cells, and in the cortex and phloem cells of roots. This study combined novel analytical approaches with controlled experimentation to examine metal hyperaccumulation in slow-growing tropical woody species, thereby enabling insight into the phenomenon not possible through field studies