title: Certain biominerals in leaves function as light scatterers.
abstract: 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.
authors.affiliation: Dept of Structural Biology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Assaf
authors.initials: A
authors.lastname: Gal
authors.forename: Vlad
authors.initials: V
authors.lastname: Brumfeld
authors.forename: Steve
authors.initials: S
authors.lastname: Weiner
authors.forename: Lia
authors.initials: L
authors.lastname: Addadi
authors.forename: Dan
authors.initials: D
authors.lastname: Oron
mesh_terms: D002119:Calcium Carbonate / Q000378:metabolism*; D002129:Calcium Oxalate / Q000378:metabolism; D030681:Ficus / Q000378:metabolism* / Q000528:radiation effects*; D005470:Fluorometry; D008027:Light; D055620:Optical Phenomena; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism* / Q000528:radiation effects*; D012542:Scattering, Radiation
chemical_list: D002129:Calcium Oxalate; D002119:Calcium Carbonate