Evidence for a transmissible factor that causes rapid stomatal closure in soybean at sites adjacent to and remote from hypersensitive cell death induced by Phytophthora sojae

In the incompatible interaction of soybean cultivar Harosoy 1272 with race 1 of P. sojae there were rapid changes in stomatal physiology following leaf inoculation. Within 2 h stomata at the infection site were fully closed and stomata located on the same leaflet that were 3 and 20 mm from the inoculation site were also closed. In contrast, in the compatible interaction of cultivar Harosoy with race 1 stomata closed only slowly or remained open at all sites. After 8 h in incompatible interactions stomata opened to preinoculation levels. Treatment of leaves with the abiotic elicitor, silver nitrate, and wounding did not induce systemic stomatal closure in either cultivar. Closure of stomata in the incompatible interaction is apparently brought about by a transmissible signal that is derived from cells that react hypersensitively to pathogen invasion.