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Photochemically produced oxidants in the atmosphere cause injury to plants primarily through inhibition of basic metabolic processes. Plants vary in their response to the oxidants and this variation must be dependent in part on the variation in metabolic activity with age or environmental conditions for growth, to a large degree not understood. Data are presented in this paper to show: (1) The changes in permeability of leaf tissue to exogenous substrate and in catabolic utilization of this substrate after exposure of plants to ozone but before visible symptoms appear; (2) The change in leaf carbohydrates as a result of exposure to ozone; (3) The protective effect of red light (700 ran) during exposure of bean plants to peroxyacetyl nitrate (PAN); (4) The correlation of sulfhydryl (SH) content in bean leaf tissue with age of plants and light regime; and (5) Effect of light regime and age of plants on incorporation of C 14 from C U-PAN by bean leaf tissue.

Ephrussi-Taylor (1954) has described a pneumococcal transforming agent which she called the LC (large colony) agent, because its first-recognized effect was to increase the size of pneumococcal colonies grown on blood agar plates. She also showed that cell suspensions of pneumococci which possess the agent have a diminished ability to respire in the presence of glucose, fail to oxidize lactate, and produce much less H202 in the course of glucose oxidation than do the normal pneumococci which do not possess this agent. Since the large colony agent seemed to act, at least in part, by blocking an enzyme responsible for the oxidation of lactic acid, it appeared desirable to characterize this enzyme. The present paper describes the partial purification of pneumococcal lactic oxidase, and provides evidence that it is a typical flavoprotein and that it is absent in the large colony strain. MATERIALS AND METHODS Pneumococcal strains. The two strains of Diplococcus pneumoniae used in this study were kindly supplied by Dr. H. Ephrussi-Taylor. One was the normal rough strain R36A derived originally from type II, and the other was made by transformation of normal R36A with the large colony agent prepared originally from the strain A66 (Ephrussi-Taylor, 1954). Throughout this paper, the normal strain of R36A and the large colony strain of R36A will be referred to as the normal and LC strains, respectively. The stock culture of the normal strain was maintained on blood heart infusion medium (Difco). The LC 1 This research was aided by grants from the American Cancer Society and from the Wallace C. and Clara A. Abbott Memorial Fund of the University of Chicago. The material in this paper is taken in part from a thesis submitted by S. Udaka in partial fulfillment of the requirements for an M.S. degree, and from a thesis submitted by J. Koukol in partial fulfillment of the requirements for a Ph.D. degree.

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