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Metabolism and Enzymology

Activities of Isolated Mitochondria and Mitochondrial Enzymes from Aerobically and Anaerobically Germinated Barnyard Grass (Echinochloa) Seedlings ¹

Department of Horticulture, The Ohio State University, Columbus, Ohio 43210-1096, Department of Botany, Duke University, Durham, North Carolina 27706

Activity of mitochondria isolated from whole seedlings of Echinochloa crus-galli (L.) Beauv. var oryzicola germinated under aerobic and anaerobic conditions for 5 to 7 days was investigated. Mitochondria from both treatments exhibited good respiratory control and ADP/O ratios. Although O₂ uptake was low in anaerobic mitochondria, activity rapidly increased when the seedlings were transferred to air. Mitochondria from both aerobically and anaerobically grown seedlings of E. crus-galli var oryzicola maintained up to 66% of their initial respiration rate in the presence of both cyanide and salicylhydroxamic acid, and the inhibitory effects of cyanide and azide were additive. In addition, antimycin A was not an effective inhibitor of respiration. Reduced-minus-oxidized absorption spectra revealed that cytochromes a, a₃, and b were reduced to a greater extent and cytochrome c was reduced to a lesser extent in anaerobically germinated seedlings relative to that in aerobically germinated seedlings. An absorption maximum in the cytochrome d region of the spectrum was reduced to the same extent under both germination conditions and an absorption maximum at 577 nm was present only in anaerobically germinated seedlings. Anaerobically germinated seedlings contained 70% of the cytochrome c oxidase activity found in air grown seedlings. Upon exposure to air, the developmental pattern of this enzyme in anaerobically germinated seedlings was similar to air controls. Succinate dehydrogenase activity in anaerobic seedlings was only 45% of the activity found in aerobically germinated seeds, but within 1 hour of exposure to air, the activity had increased to control levels. The results suggest that mitochondria isolated from E. crus-galli var oryzicola differ from other plants studied and that the potential for mitochondrial function during anaerobiosis exists.

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				T. Fukao, R. A. Kennedy, Y. Yamasue, and M. E. Rumpho Genetic and biochemical analysis of anaerobically-induced enzymes during seed germination of Echinochloa crus-galli varieties tolerant and intolerant of anoxia J. Exp. Bot., May 1, 2003; 54(386): 1421 - 1429. [Abstract] [Full Text] [PDF]