DEVELOPMENT OF FLUORESCENT, HYPERSENSITIVELY NECROTIC CELLS CONTAINING PHYTOALEXINS ADJACENT TO COLONIES OF XANTHOMONAS-CAMPESTRIS PV MALVACEARUM IN COTTON LEAVES

During the hypersensitive response of resistant cotton leaves to attempted bacterial infection and during the period of phytoalexin accumulation, mesophyll cells closest to bacterial colonies developed yellow-green autofluorescence and, later, brown pigmentation. Susceptible leaves, which accumulate less of the phytoalexins, developed fewer fluorescent cells. Filter sets designed for fluorescence-microscope observation of fluorescein are fortuitously selective for the autofluorescent cells. Videodensitometry showed that all such cells exhibited substantially less fluorescence after mild extraction. The two phytoalexins which are green fluorescent accounted for 75% of the green fluorescent material extracted from inoculated resistant leaves. It was concluded that all yellow-green fluorescent cells contain diffusible phytoalexins. © 1992.