Dept of Structural Biology, Weizmann Institute of Science, Rehovot, Israel.
Adv Mater. 2012 Mar 8;24(10):OP77-83. doi: 10.1002/adma.201104548. Epub 2012 Jan 31.
Cystoliths are amorphous calcium carbonate bodies that form in the leaves of some plant families. Cystoliths are regularly distributed in the epidermis and protrude into the photosynthetic tissue, the mesophyll. The photosynthetic pigments generate a steep light gradient in the leaf. Under most illumination regimes the outer mesophyll is light saturated, thus the photosynthetic apparatus is kinetically unable to use the excess light for photochemistry. Here we use micro-scale modulated fluorometry to demonstrate that light scattered by the cystoliths is distributed from the photosynthetically inefficient upper tissue to the efficient, but light deprived, lower tissue. The results prove that the presence of light scatterers reduces the steep light gradient, thus enabling the leaf to use the incoming light flux more efficiently. MicroCT and electron microscopy confirm that the spatial distribution of the minerals is compatible with their optical function. During the study we encountered large calcium oxalate druses in the same anatomical location as the cystoliths. These druses proved to have similar light scattering functions as the cystoliths. This study shows that certain minerals in the leaves of different plants distribute the light flux more evenly inside the leaf.
结石是无定形碳酸钙体，形成于一些植物科的叶子中。结石在表皮中均匀分布，并突出到光合作用组织——叶肉中。光合作用色素在叶片中产生陡峭的光梯度。在大多数光照条件下，外部叶肉达到光饱和，因此光合作用装置在动力学上无法利用多余的光进行光化学。在这里，我们使用微尺度调制荧光法证明，由结石散射的光从光合作用效率低下的上部组织分布到有效但受光限制的下部组织。结果证明，光散射体的存在降低了陡峭的光梯度，从而使叶片能够更有效地利用入射光通量。微 CT 和电子显微镜证实，矿物质的空间分布与其光学功能相匹配。在研究过程中，我们在与结石相同的解剖位置遇到了大的草酸钙晶簇。这些晶簇被证明具有与结石相似的光散射功能。本研究表明，不同植物叶片中的某些矿物质在叶片内部更均匀地分配光通量。
