Some Effects of Decay and Weathering on the Anatomical Structure of the Stem of Phragmites Australis Trin. Ex Steud.

Abstract

Effects of decay and weathering on the stems of Phragmites australis Trin. ex Steud. were studied on material used for thatching. Decay appeared to be mainly a result of fungal attack and ultra-violet radiation. Biological degradation by soft-rot fungi causes a considerable loss of cell wall constituents towards the exposed basal part of the stems. In sclerenchyma and parenchyma (excl. the subepidermal tissues) this effect is visible as diamond-shaped cavities, spirally arranged in the central part of the secondary cell walls (following the microfibrillar arrangement). A second type of fungal attack is observed in stems obtained from a byre. Here the cell walls are thinned from the lumen side towards the external wall layers, showing in longitudinal section cells with locally enlarged lumina. At the exposed parts of the stem superficial weathering by ultra-violet radiation causes degradation of lignin. Thus the middle lamella region disintegrates and the outer cell layers peel off.