Department of Ecology, Environment and Evolution, La Trobe University, Bundoora, Vic 3086, Australia.
Analytical Electron Microscopy Laboratory, La Trobe University, Bundoora, Vic 3086, Australia.
Tree Physiol. 2018 Jan 1;38(1):119-128. doi: 10.1093/treephys/tpx099.
Gossia, a small genus of physiologically novel rainforest trees restricted to the Western Pacific and belonging to a key neotropical Southern Hemisphere family, the Myrtaceae, is characterized by high foliar manganese (Mn) concentrations. This field study provides a quantitative in planta snapshot detailing cellular localization of foliar Mn and other mineral nutrients in sympatric Gossia grayi N. Snow & Guymer and Gossia shepherdii N. Snow & Guymer endemic to far northeastern Australia, and previously not examined. Elements localized in the cells of fresh hydrated leaf tissues were quantified via in vivo cryo-scanning electron microscopy energy dispersive spectroscopy, a non-invasive method that effectively immobilizes cell contents. Leaf anatomical differences were found between species, along with foliar Mn spatial distribution patterns. Localized cellular Mn concentrations exceeding 600 mmol kg-1 were detected in G. shepherdii, whose Mn accumulation across different mesophyll cell types was heterogeneous compared with G. grayi. In both species there was little evidence to support previous findings on other Gossia species of carboxylate association with excess Mn. The analytical X-ray data strongly implicated chloride as a counter-ion to Mn in the two species examined here. The key findings align with the hypothesis that Mn disposal in the mesophyll is a generic trait in Gossia. This research has forged an emerging view of Gossia as being characterized by unusual cellular metal and mineral accumulation patterns that vary at the species level. It contributes to current limited knowledge about generic plant metallophyty, highlighting that assimilating a broader perspective of the phenomenon demands evaluation of individual taxa through field studies.
高西亚属是一个生理上新颖的热带雨林树种小属，局限于西太平洋，属于一个关键的新热带南半球科，桃金娘科，其特征是叶片锰（Mn）浓度高。这项野外研究提供了一个定量的活体快照，详细描述了同域分布于澳大利亚东北部的高西亚·格雷伊 N. 斯诺和盖默和高西亚·谢泼德 N. 斯诺和盖默叶片 Mn 和其他矿物养分的细胞定位，此前尚未对此进行检查。通过体内冷冻扫描电子显微镜能量色散光谱法对新鲜水合叶片组织细胞中定位的元素进行定量分析，这是一种有效的非侵入性方法，可有效地固定细胞内容物。发现物种之间存在叶片解剖差异以及叶片 Mn 空间分布模式。在 G. shepherdii 中检测到超过 600 mmol kg-1 的细胞内 Mn 浓度，其 Mn 在不同的叶肉细胞类型中的积累与 G. grayi 相比是不均匀的。在这两个物种中，几乎没有证据支持以前在其他高西亚物种中发现的羧酸盐与过量 Mn 相关的发现。分析 X 射线数据强烈表明，在本研究中检查的两个物种中，氯是 Mn 的抗衡离子。主要发现与 Mn 在叶肉中的处置是高西亚属的一般特征的假设一致。这项研究形成了一种新兴的观点，认为高西亚属的特征是其细胞金属和矿物质积累模式在物种水平上存在差异。它丰富了目前关于一般植物金属植物的有限知识，强调通过野外研究评估个别分类群，可以更好地了解这一现象。
