The effect of desiccation on cell shape in the lichen Parmelia Sulcata taylor

Abstract

Comparisons have been made of the shape of algal cells in the lichen Parmelia sulcata which was subjected to controlled desiccation regimes inducing substantial water loss. The spherical appearance of algal cells obtaiiíed by conventional techniques for transmission electrón microscopy (TEM) was shown by low temperature scanning electrón microscopy (LTSEM) to be the consequence of rapid rehydration during fixation. Collapse of the walls of algal cells and fungal hyphae in the medulla and algal layer when desiccated were observed with LTSEM and shown to be reversible on rehydration. Desiccation-induced contraction of cortical fungal protoplasts was detected with LTSEM. Fixation with osmium vapour only before TEM demonstrated a similar contraction of algal protoplasts.