In vivo localization of manganese in the hyperaccumulator Gossia bidwillii (Benth.) N. Snow & Guymer (Myrtaceae) by cryo‐SEM/EDAX

Abstract

Gossia bidwillii (Myrtaceae) is a manganese (Mn)-hyperaccumulating tree native to subtropical eastern Australia. It typically contains foliar Mn levels in excess of 1% dry weight. However, in G. bidwillii and other Mn-hyperaccumulating species, the cellular and subcellular localization of Mn has not been measured. Quantitative in vivo cryo-scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDAX) was used to localize Mn and other elements in tissue collected from mature trees growing in a natural population. Cryo-SEM showed that the leaf mesophyll is differentiated as a double-layer palisade mesophyll above spongy mesophyll. Transmission electron microscopy (TEM) revealed that the palisade and epidermal cells are highly vacuolated. EDAX data were used to estimate in situ vacuolar Mn concentrations of all cell types in fresh cryo-fixed leaf tissues. The highest average vacuolar Mn concentration of over 500 mM was found in the upper-layer palisade mesophyll, while the lowest concentration of around 100 mM was found in the spongy mesophyll. Qualitative in vivo cryo-SEM/EDAX was employed to further investigate the spatial distribution of Mn in fresh leaf tissues and young bark tissue, which was also found to have a high Mn concentration. It is concluded that Mn distribution in G. bidwillii is quantitatively different to metal distribution in other hyperaccumulating species where the highest localized concentrations of these elements occur in non-photosynthmetic tissues such as epidermal cells and associated dermal structures including trichomes and leaf hairs.

Arsenic hyperaccumulation and localization in the pinnule and stipe tissues of the gold-dust fern (Pityrogramma calomelanos (L.) Link var. austroamericana (Domin) Farw.) using quantitative micro-PIXE spectroscopy

“…Recently, Fernando et al (2006a) employed micro-PIXE analysis on cryofixed, freeze-dried leaves of two Mn hyperaccumulating (Gossia bidwillii and Virotia neurophylla) and two Mn accumulating (Macadamia integrifolia and Macadamia tetraphylla) tree species, and observed that Mn was localized in the palisade mesophyll of all four species. Interestingly, authors commented that the localization pattern of Mn in Gossia bidwillii obtained using micro-PIXE, agreed with their earlier study (Fernando et al 2006b) where Mn localization of cryo-planed frozen-hydrated leaf tissues of the same species was investigated using EDXA. Fernando et al (2006a) noted that Mn is an integral component of photosynthesis and as such, could be viewed as 'less phytotoxic' than other hyperaccumulated elements.…”

Manganese tolerance and accumulation in six Mn hyperaccumulators or accumulators

“…We did not find evidence in this hydroponics experiment to classify C. dactylon as a Mnhyperaccumulator, as experimental conditions of the two studies were different, thus further detailed experiments need to be conducted in real soil cultivation. Since the Mn spatial accumulations of the three selected hyperaccumulators in the shoots and especially in leaves remain unclear, future experiments should measure the spatial accumulation in either the foliage's photosynthetic or nonphotosynthetic tissues, such as the palisade cell layers, epidermal tissues, or dermal tissues, depending on the species (Fernando et al 2006a(Fernando et al , b, 2008a.…”

“…Well-known Mn hyperaccumulators, plants capable of acquiring more than 10,000 mg kg −1 of Mn (dry weight) in its aboveground biomass (Xu et al 2006), include the Gossia bidwillii and Austromyrtus bidwillii from Eastern Australia (Bidwell et al 2002;Fernando et al 2006a), nine species listed by Reeves and Baker, and an unidentified Eugenia species described by Sabah (Proctor et al 1989). In addition, Japan is well known for the accumulator Eleutherococcus sciadophylloides that can sequester up to 7,900 mg.g −1 Mn in the leaf dry matter (Memon et al 1980).…”

Variability of Mn hyperaccumulation in the Australian rainforest tree Gossia bidwillii (Myrtaceae)

“…N. Snow and Guymer, an Australian tree that hyperaccumulates Mn, primary sequestration of foliar Mn in naturally growing plants was found to occur in the photosynthetic tissues, a pattern previously undescribed in other hyperaccumulating plants (Fernando et al 2006b). This has since been observed in naturally occurring Virotia neurophylla (Guillaumin) Virot (Proteaceae), the Mnhyperaccumulating tree species endemic to New Caledonia (Fernando et al 2006a).…”