剑桥大学在虎耳草属植物中发现稀有矿物
近日,英国剑桥大学的研究人员在国际上首次发现一些虎耳草属(Saxifraga)高山植物的叶片可以产生稀有矿物球霰石,相关研究结果以论文“Leaf margin organisation and the existence of vaterite-producing hydathodes in the alpine plant Saxifraga scardica”发表在《Flora》杂志。
球霰石即μ-CaCO3,是碳酸钙的一种不太稳定的结晶形态,在自然界中非常稀有,之前曾在一些海洋和淡水甲壳动物、鸟卵、鲑鱼的内耳、陨石和岩石中发现少量球霰石晶体。这是第一次在植物中发现产生该矿物。球霰石具有负载能力高、细胞高吸收率和溶解性等特性,有潜力成为一种很好的缓释药物载体,在制药行业发挥作用。
此外,研究者还发现,一种虎耳草属植物(Saxifraga scardica)的叶片细胞有特殊的新型细胞壁结构,似乎可以将叶片边缘的光线转移到叶片中间,从而帮助在阴暗环境下生长的植物收集更多的光线。研究这种新型细胞壁结构,有助于研发新型的生物激发光学器件和光子结构。
相关发现有赖于剑桥大学显微镜核心设施的新型显微镜技术。低温扫描电子显微镜可快速冷冻样品并在真空下保持低温,给研究者提供了详细观察“天然”水合状态下的细胞和植物组织的机会。而拉曼显微镜能够识别化合物分子,不仅能够确定是碳酸钙,而且能够区分方解石和球霰石两种结晶形态。
Abstract
Some sections of species within the genus Saxifraga deposit a chalky crust on the surface of their leaves, originating from the guttation medium produced by the sunken hydathodes found generally at or near the leaf margin. The organisation of the hydathode tissues, that of the rest of the leaf and the physiology of the crust is poorly understood. We have used cryo-SEM and cryo-fracture to study leaf tissue organisation and structure in Saxifraga scardica and compared it to the imaging data with the previously characterised Saxifraga cochlearis. We find S. scardica contains a transparent and tapered leaf margin containing thick walled cylindrical cells that may serve to deflect light to the adjacent palisade mesophyll tissue. Raman microscopy reveals the S. scardica leaf crust contains the rare and metastable calcium carbonate polymorph vaterite whereas the crust from S. cochlearis contains only calcite. Vaterite-crust is also observed on the leaves of some species within the section Porphyrion but is not found on members of the section Ligulatae. The implications of these findings are discussed.