Manganese accumulation in the leaf mesophyll of four tree species: a PIXE/EDAX localization study

Abstract

Summary• Little is known about the spatial distribution of excess manganese (Mn) in the leaves of tolerant plants. Recently, the first such study of a Mn hyperaccumulator showed that the highest localized Mn concentrations occur in the photosynthetic tissue. This is in contrast to reports based on localization of foliar accumulation of other heavy metals.• Here, four tree species, Gossia bidwillii , Virotia neurophylla , Macadamia integrifolia and Macadamia tetraphylla , which hyperaccumulate or strongly accumulate Mn, were studied. Cross-sectional foliar Mn localization was carried out in situ using proton-induced X-ray emission/energy dispersive X-ray analysis (PIXE/EDAX).• All four species contained photosynthetic tissues with multiple palisade layers. These were shown to be the primary sequestration sites for Mn. Mn was not detected in the epidermal tissues.• The findings of this study demonstrate a concurrence of three traits in four tree species, that is, accumulation of excess Mn in the leaves, its primary sequestration in the photosynthetic tissues, and multiple-layer palisade mesophyll.

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

“…To our knowledge, there have been no micro-PIXE studies on As hyperaccumulators, with the majority of studies focused on Ni hyperaccumulators (Bhatia et al 2004;Budka et al 2005;Mesjasz-Przybyłowicz et al 2001), with a single study on a Mn hyperaccumulator (Fernando et al 2006a) and Cd accumulator (Ager et al 2002). Moreover, there are no studies that address As localization in species other than P. vittata and P. cretica var.…”

“…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. However, this same reasoning does not justify the localization pattern of As observed in our study suggesting other strategies in addition to cellular localization may be responsible for As homeostasis in P. calomelanos var.…”

“…In Cd and Zn hyperaccumulator, Thlaspi caerulescens, Ma et al (2005) reported 2-fold higher Cd and Zn concentrations in epidermal tissues as compared to mesophyll tissues, however 65-70% of absolute leaf Cd and Zn were present in mesophyll tissues. 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.…”

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). In both cases, the highest concentrations of foliar Mn were found in the multiple-layer palisade mesophyll.…”

“…Plants from sites 1 and 2 were sampled, prepared and analysed as described in Fernando et al (2006a). Three trees from each site were examined.…”