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The cytochrome c3 of Desulfovibrio desulfuricans and that of D. vulgaris were purified to homogeneity as judged by disc gel electrophoresis and by ultracentrifugation. Both cytochromes had an oxidation-reduction potential of-205 5 mv atpH 7.0 and showed characteristic absorption bands at 525 and 553 nm in the reduced state. The molecular weights of the two cytochromes (calculated from sedimentation and diffusion data) were similar, with values of 13,500 to 14,300 for D. desulfuricans and 13,800 to 14,700 for D. vulgaris. The two cytochromes differed in their electrophoretic properties on Geon and polyacrylamide gel electrophoresis and did not share a common precipitating antigenic determinant as judged by immunodiffusion data.

Neurospora crassa strain 74A grown on Vogel's medium containing bovine serum albumin (BSA) as principal carbon source secretes proteolytic enzymes which appear in the culture filtrate. Low concentrations of sucrose (0.1%) are necessary for growth from conidia, as conidia will not germinate on BSA alone. Once growth is initiated, however, protease production begins and at 5 to 6 hr growth and enzyme production are parallel. Higher concentrations of sucrose (0.5-2%) repress protease synthesis. Other metabolizable materials (sugars, amino acids, peptide mixtures) also repress protease synthesis. Some sugars will not sustain growth but allow germination and full induction of protease in the presence of protein. A material found in culture fluids of cells during induction of protease synthesis when added to repressed cultures causes a five-fold increase in the amount of protease production, although this is still approximately half that of normally induced cells. This material appears to be produced by induced cells in as little as 2 hr of culture, which is before detectable levels of protease can be found. It is heat-stable, of low molecular weight, and is not a simple product of protein digestion by the N. crassa proteases.

The gross tissue distribution, intraceRular fate, and chemical behavior of Ni2+ in soybean plants (Glycine max cv. Williams) were investigated.Following root absorption, Ni was highly mobile in the plant, with leaves being the major sink in the shoots for Ni during vegetative growth. A senescence >70% of the Ni present in the shoot was remobilized to seeds. Fractionation of root and leaf tissues showed >90% of the Ni to be associated with the soluble fraction of tissues; ultrafiltration of the solubles showed >77% of the Ni to be associated with the 10,000 to 500 molecular weight components of both roots and leaves. Chemical characterization of the soluble components (10,000 to 500 and >500 molecular weight) by thin layer chromatography and electrophoresis resolved a number of Ni-containing organic complexes. Major Ni-containilng components formed in the root are transported in the xylem stream, and undergo partial modification on deposition in leaves. Nickel accumulated in seeds is primarily associated with the cotyledons. Chemical fractionation of cotyledon components showed 80% of the Ni to be associated with the soluble whey fraction, while 70% of this fraction was composed of Ni-containing components with molecular weight <10,000.Plants are known to accumulate Ni readily (9), and unlike most nonessential elements, Ni is mobile in plants and accumulated in seeds (9). The unusual behavior of Ni in plants may be a result of its behavior as an analog of Cu and Zn as shown in root transport studies (3). If Ni behaves as an analog (functional or nonfunctional) of essential nutrients in plants, the metabolic potential may exist to alter its chemical form and thereby alter its potential for uptake and toxicity to successive trophic levels. Studies on the toxicological aspects of Ni in animal systems (5, 6) suggest that organonickel compounds and complexes are more toxic than inorganic forms of Ni.Relatively few studies have been concemed with the form of metals in plant tissues. Investigations of the form of cations such as Fe, Cu, Zn, and Mn in leaf tissues of agronomic species (2,8) (14) has shown that Ni transported in the xylem fluid of crop plants was present as an anionic complex that had similar electrophoretic behavior in five species. In addition, Tiffm demonstrated that the form of Ni in exudate was dependent on metal concentration in xylem fluid. In tomato, a cationic Ni complex was found in the xylem in addition to the anionic form when physiological levels (<3 ,M) in the xylem were exceeded. This latter observation indicates a need for care in defining the fate and chemical form of metals in plants, since the plant-available concentration oftrace elements in the environment will generally be low.Although studies have dealt with specific aspects ofthe behavior of Ni in plants, none have fully described the fate of Ni following root absorption, vegetative growth, and senescence. The present study describes the over-all behavior of Ni2" in soybean plants by evaluating its gross distribution and fa...