Abstract
Conventional and analytical electron microscopy (EDX, ESI, EELS) were used to investigate
the silicon accumulation, the chemical nature of the Si deposits and their formation
in three species of monocotyledons. In Deschampsia, in particular parts of the outer epidermal cell wall silicon is accumulated as silicic
acid. Electron dense, needle-shaped crystals in the vacuoles of epidermal cells and
in the intercellular spaces were also identified as silicic acid. In xylem parenchyma
cells, silicon is accumulated as SiO2, which is formed from Sn silicate. In Festuca, crystal-like deposits of SiO2 occur on the epidermal surface, in the epidermal and parenchyma cell walls, and in
vacuoles of bundle sheath cells. Often the deposits disturb the cell walls and penetrate
the envelope of plastids and mitochondria. The crystal-like SiO2 deposits originate from Sn silicate. In the pericarp of ripe nuts of Schoenus, no stainable cell wall components are detected. The inner part of the pericarp consists
of silicic acid, while in the outer regions small clusters of silicic acid are embedded
in a matrix of SiO2. The silicic acid deposits show an unusual, layered structure, typical for lepidoic
silicic acids, which consist of two-dimensional crystals lying one above the other.
Key words
SiO2
- silicic acid - monocotyledons - EDX - ESI - EELS
