Silica and Ash in Tissues of Some Plants Growing in the Coastal Area of Mississippi, USA

Ash and silica contents and their depositional patterns in differenttissues of 27 plants growing in the Ocean Springs area of Mississippi(many grow elsewhere), were determined. Silica content of driedplant parts varied from no more than 0 per cent in Borrichiafrutescens (L.) D.C. stems to 18.76 per cent in Arundinariagigantea (Walt.) Muhl. leaves. Ash content varied from 0·73per cent in Cliftonia monophylla (Lam.) Britt. ex Sarg. stemsto 44·02 per cent in Batis maritima L. leaves. Plantssuch as Batis maritima L., Borrichia frutescens (L.) D.C., Salicorniabigelovii Torr. and Salicornia virginica L. which grew in salinemarshes had high ash contents due NaCl in their tissues. Morusrubra L. leaves had a high silica content for a dicotyledonousplant (3·12 per cent). Energy-dispersive X-ray analysisshows that the distribution of the element silicon is clearlyrelated to certain epidermal structures such as ridges, cellwalls, rows of irregular shaped structures lengthwise of theleaf, dumb-bell shaped ones and especially in trichomes. Therewas a high concentration of silica containing trichomes alongthe veins on the underside of Morus rubra L. leaves and thiswould protect them from insects. The outer parts of the inflorescencesof Ctenium aromaticum (Walt.) Wood, Elymus virginicus L., Juncuspolycephalus Michx. and phragmites communis Trin. were highlysilicified. This should give the seed some protection from insects.The sharp particles would be irritating to oesophageal tissuesand might be implicated in such a cancer.