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Ultrastructural Cell Wall Alterations in Immune Cotton Leaves Inoculated with Xanthomonas malvacearum. Edward T. Cason, Jr., Langston Research Program, Langston University, Langston, OK 73050, Present address of senior author: Shell Chemical Company, 10050 Regency Circle, Suite 306, Omaha, NE 68114; P. E. Richardson(2), M. K. Essenberg(3), L. A. Brinkerhoff(4), W. M. Johnson(5), and R. J. Venere(6). (2)(3)School of Biological Sciences and Department of Biochemistry, respectively, Oklahoma State University, Stillwater, OK 74074; (4)(5)(6)Langston Research Program, Langston University, Langston, OK 73050. Phytopathology 68:1015-1021. Accepted for publication 2 February 1978. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1015.

Within 2 hr following inoculation of immune cotton cotyledon tissue incompatible bacteria in the intercellular spaces caused disruptions on the outer surfaces of host mesophyll cell walls. These disruptions were characterized by loosening and detachment of the surface cuticle and envelopment of adjacent bacteria. The enveloping structures contained one to several bacteria and were filled with wispy fibrillar material apparently released from the damaged cell wall. The plasmalemma frequently was broken in the vicinity of enveloped bacteria, and host cytoplasm appeared to be clumped and electron-dense. Inoculated tissue became necrotic within 24 hr. Cell walls of similarly inoculated susceptible host tissue were not disrupted during the test period, and intercellular bacteria were not enveloped. These observations suggest that in immune cotton leaves, cell wall damage may lead to membrane breakage and cell necrosis.

Additional keywords: Hypersensitive response (HR), Gossypium hirsutum L., compatibility, incompatibility.