Respiration during seed maturation

The contribution of cytochrome and alternative pathways to respiration during soybean Glycine max (L.) Merr. cv. Chippewa 64] seed formation and maturation was measured by oxygen consumption of embryonic axis and cotyledon tissues and of mitochondria isolated from immature seeds. Respiration rates (dry weight basis) declined duing the last month of seed maturation. Cyanide sensitive respiration (cytochrome pathway) accounted for 80 to 90% of total oxygen consumption throughout seed formation and maturation. The proportion of the total respiration resistant to 1 m M cyanide and inhibited by 1 m M salicylhydroxamic acid (alternative pathway) did not exceed 6%. A residual oxygen consumption, accounting for 5 to 15% of total respiration, persisted in the presence of both inhibitors. Likewise, virtually no alternative respiration was found in mitochondria prepared from immature seeds. The alternative respiratory pathway seems absent during soybean seed formation and maturation regardless of whether grown in the greenhouse or field.