Developmental analysis and optical modelling of short cell phytoliths in Festuca exaltata (Poaceae)

Short cells of Poaceae often contain a cell lumen (CL) phytolith. The aim of this investigation was to analyse the features, development and possible function of CL phytoliths in Festuca exaltata leaves. This study employed light microscopy (LM), scanning and transmission electron microscopy (SEM and TEM respectively). The interaction of light with these phytoliths was modeled using the Finite-Difference Frequency Domain (FDFD) method. The results showed that silica deposition begins within a medium electron density matrix. Proteins were detected in the center of the cytoplasm in a higher amount during the young stage. This occurrence suggests that proteins may be a possible component of the matrix or at least play a role in the silica deposition. At maturity, the short cell phytoliths have peculiar morphology and positioning. These were tested numerically to verify their possible role in either conveying or deflecting light rays, showing only a negligible influence of the phytoliths on the distribution of light within the leaf. A channel apparently connects the silica and the cork cell, suggesting that the cork cells have a metabolic activity related to the metabolism of the silica cells, but possibly not exclusively related to the development.