Relationship of Alternative Respiratory Capacity and Alternative Oxidase Amount during Soybean Seedling Growth

In soybean (Glycine max [L.] Merr.) axis tissue and light- and dark-grown cotyledons 3 to 9 days of age, increasing amount of alternative oxidase corresponded with the increasing alternative pathway capacity of isolated mitochondria from these tissues. From 9 to 12 days of age, however, little or no change in amount of alternative oxidase occurred in cotyledons even though there were substantial changes in capacity. This suggests that, whereas alternative oxidase content may be important in determining the capacity of the alternative pathway in young cotyledons and in axis tissue, other factors regulate capacity in older cotyledons. Both the presence or absence of light and tissue type (cotyledon or axis) were found to influence the observed pattern on immunoblots of proteins believed to constitute the alternative oxidase.