Recognition of a pathogen and a nonpathogen by barley coleoptile cells. II. Alteration of cytoplasmic strands in coleoptile cells caused by the pathogen, Erysiphe graminis, and the nonpathogen, E. pisi, prior to their penetration

Abstract

Cytoplasmic responses of barley coleoptile cells to Erysiphe pisi and E. graminis , a nonpathogen and a pathogen of barley, respectively, were examined during the times between inoculation and penetration to identify the location and number of cytoplasmic strands at interaction sites. The location and number of cytoplasmic strands within a single cell were determined from micrographs taken at different focal planes within a cell. When either fungus failed to penetrate, cytoplasmic strands were located beneath appressoria prior to initiation of the cytoplasmic aggregate. In cases where E. graminis germlings eventually succeeded in penetration, cytoplasmic strands were located not only under appressoria but also in the entire cells. The number of cytoplasmic strands ranged from 4 to 6 in uninoculated cells. When cells had been inoculated, the number of strands increased to 9-18 between the times of appressorial maturation and attempted penetration when either fungus eventually failed to penetrate. However, the number of strands remained unaltered prior to actual penetration when E. graminis eventually succeeded in penetration. These observations suggest that physiological changes affecting the success or failure of penetration by inoculated fungi occur in coleoptile cells prior to the time of actual penetration.