Silica and Ash in Tissues of Some Coastal Plants

Ash and silica contents and their depositional patterns in different tissues of 44 Mississippi coastal plants were determined. Silica content of dried plants varied from no more than a trace in Chenopodium album L. leaves to 7.37 per cent in Zizanopsis miliacea (Michx) Doell & Aschers leaves. Ash content varied from 2.50 per cent in Lythrum lineare L. stems to 28.24 per cent in Borrichia frutescens (L.) DC leaves. Plants in the same family tend to be alike in their ability to absorb or not absorb silica. Poaceae and Cyperaceae had consistently high concentrations of silica. In contrast, the Asteraceae studied had very low silica contents but often had high contents of other minerals. Dicotyledonous plants studied had consistently lower silica contents than the monocotyledons. Plants growing in salt water contained considerable sodium chloride. Spectra were obtained for major elements in four different plants. Energy-dispersive X-ray analysis shows that distribution of the element silicon is clearly related to certain epidermal structures such as guard cells, ridges, dumb-bells and balls that appear in electron micrographs. Silica was deposited differently in each type of plant studied. In many of the plants silica was deposited in rows of irregular-shaped particles running lengthwise of the leaf and in guard cells. In others, like Zizanopsis miliacea (Michx) Doell & Aschers, the deposit was sheet-like. Zizania aquatica L. not only had a sheet-like deposit, but the deposit was ridged and there were rows of dumb-bell-shaped silica cells. Related plants had similar structures. Euchlaena mexicana Schrad., Tripsacum dactyloides (L.) L and Manisuris rugosa (Nutt.) Kuntze all had irregular phytoliths similar to those in Zea mays L.