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Physiology and Biochemistry

The Effects of Septoria nodorum and Xanthomonas translucens f. sp. undulosa on Photosynthesis and Transpiration of Wheat Flag Leaves. J. B. Jones, Former graduate assistant, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061, Present address of senior author: Agricultural Research and Education Center, Bradenton, FL 33508; C. W. Roane(2), and D. D. Wolf(3). (2)Professor, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061; (3)Associate professor, Department of Agronomy, Virginia Polytechnic Institute and State University, Blacksburg 24061. Phytopathology 71:1173-1177. Accepted for publication 23 February 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1173.

In photosynthetic studies, either Xanthomonas translucens or Pseudomonas cepacia was applied in combination with Septoria nodorum to flag leaves of wheat at the 50% heading stage. Apparent photosynthetic rate (APR) and transpiration rate of flag leaves did not differ statistically in the X. translucens + S. nodorum treatment compared with S. nodorum alone. An interaction may have occurred when plants were incubated at 24 C; however, at lower incubation temperatures, combined inoculation had no effect compared with inoculation with either organism alone. Flag leaves had higher APR and transpiration rates when P. cepacia was applied at the same time as S. nodorum. S. nodorum may affect photosynthesis by reducing stomatal aperture and concomitantly transpiration. P. cepacia appears to be a very effective antagonist when applied at the same time as S. nodorum.