Intracellular Silica Deposition in Mature and Senescent Leaves of Sieglingia decumbens (L.) Bernh

Following 1, 2, 4, or 8 weeks of growth in a silica-minimal solution, tillers of Sieglingia decumbens (Heath Grass) were transferred for 8 days to a nutrient solution which contained 50 or 100 ppm silica. The resultant formation of intracellular opal phytoliths (silica bodies) was compared for the four developmental stages of leaf 3. Characteristically different phytolith types occurred in leaves of different ages. Senescent, in contrast to younger, mature leaves, typically exhibited extensive extracellular silicification of the mesophyll, in addition to deposits in stomatal, long, and bulliform cells of adaxial epidermis; deposition in abaxial silica cells and long cells, characteristic of young leaves, was much reduced, or absent. Physico-chemical factors and cytoplasmic changes associated with senescence are discussed in relation to intracellular opal phytolith formation in mature leaves of S. decumbens. In this respect, the tendency of silicic acid sols to polymerize in the presence of an organic matrix and mineral cations is considered to be significant.