Browsing by Author "Marshall, AT"

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    Electron and ion microprobe analysis of calcium distribution and transport in coral tissues
    (Company of Biologists, 2007-07-15) Marshall, AT; Clode, PL; Russell, RA; Prince, KE; Stern, R
    It is shown by x-ray microanalysis that a gradient of total intracellular Ca concentration exists from the outer oral ectoderm to the inner skeletogenic calicoblastic ectoderm in the coral Galaxea fascicularis. This suggests an increase in intracellular Ca stores in relation to calcification. Furthermore, Ca concentration in the fluid-filled space of the extrathecal coelenteron is approximately twice as high as in the surrounding seawater and higher than in the mucus-containing seawater layer on the exterior of the oral ectoderm. This is indicative of active Ca2+ transport across the oral epithelium. Polyps were incubated in artificial seawater in which all 40Ca was replaced by 44Ca. Imaging Ca2+ transport across the epithelia by secondary ion mass spectroscopy (SIMS) using 44Ca as a tracer showed that Ca2+ rapidly entered the cells of the oral epithelium and that 44Ca reached higher concentrations in the mesogloea and extrathecal coelenteron than in the external seawater layer. Very little Ca2+ was exchanged in the mucocytes, cnidocytes or zooxanthellae. These observations again suggest that Ca2+ transport is active and transcellular and also indicate a hitherto unsuspected role in Ca2+ transport for the mesogloea. © 2007, Company of Biologists
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    Multiple metal accumulation within a manganese-specific genus
    (Botanical Society of America, 2013-04) Fernando, DR; Marshall, AT; Forster, PI; Hoebee, SE; Siegele, R
    Premise of the study: Plants that strongly accumulate metals may be practically beneficial, and also serve as novel resources for increasing fundamental understanding of plant biology. Australian Gossia (Myrtaceae) species are delineated by a conspicuous affinity for the heavy metal manganese (Mn), which is a micronutrient crucial to photosynthesis. This genus includes several Mn hyperaccumulators such as G. bidwillii. Unusually, in G. bidwillii foliar Mn is most highly concentrated in photosynthetic cells, an observation thus far restricted to foliar-Mn accumulation in Mn hyperaccumulators. Recent discovery that several of these Gossia species accumulate other metals in addition to Mn will enable investigation as to whether primary sequestration of metals in photosynthetic tissues is restricted to Mn. Methods: Gossia species known to accumulate nickel (Ni) or aluminum (Al) in addition to Mn were sampled in the field. Complementary proton- and electron-probe data were combined to evaluate in vivo microdistribution patterns of excessively accumulated foliar metals. • Key results: It was discovered that in addition to Mn and Ni, Gossia fragrantissima accumulated foliar zinc (Zn) and cobalt (Co), with Mn, Ni, and Co most highly localized in mesophyll cells and Zn primarily located in the upper epidermis. In G. hillii, Mn and Al were highly concentrated in the palisade and epidermis, respectively. Conclusions: This investigation provides evidence that the primary disposal of excess foliar metals in photosynthetic cells is not exclusive to Mn. It offers rare intrageneric perspective on metal compartmentation, pointing to significant variation among tonoplastal metal transporters associated with detoxification. © 2013, Botanical Society of America.