Bacteria as a cause of vascular occlusion in cut fronds of Adiantum raddianum: a scanning electron microscope study

Abstract

Using conventional scanning electron microscopy as well as cryo-scanning electron microscopy the cut surface of the petiole of the fern Adiantum raddianum Presl. was found to be covered by bacteria, within 2 days of placing the leaf (frond) in water. An accompanying amorphous substance was also observed, especially when using cryo-scanning electron microscopy. Within 2 days only a few bacteria were observed inside the xylem, but some xylem conduits contained the amorphous substance. After 4 days, bacteria were also found inside the xylem. Bacteria accumulated at the pit-membranes and occasionally filled the entire tracheid lumen. The development of both a bacterial population at the cut surface of the petiole and an amorphous substance inside the conducting elements preceded the rapid wilting of the cut fern leaves.