Plant Respiration

Plants possess an energetically wasteful respiratory pathway in their mitochondria termed the alternative pathway. Large amounts of potential harvested crop yield may be lost through the operation of this pathway. Although the role of the alternative pathway in metabolism is not known, it is found in all plants, suggesting an important metabolic function. Knowing under what circumstances electrons derived from respiratory substrates are diverted from the main, energy-producing respiratory pathway onto the alternative pathway is crucial to discovering the alternative pathway's role. Studies of the distribution of electrons between the two respiratory pathways are possible through a technique based on differential use of the stable isotope oxygen-18 by the two oxidases that terminate the two pathways. The continued development and application of this technology will allow characterization of alternative pathway activity during respiration by intact plant tissues responding to two environmental stresses, low temperature and phosphorus deprivation. These studies will be carried out using plants having the "normal" alternative oxidase, the enzyme that comprises the alternative pathway, and transgenic plants expressing an altered form of the enzyme that cannot be inactivated by normal regulatory mechanisms. This research will improve our understanding of conditions under which the alternative pathway is active, which is essential for any future agricultural application of transgenic plants with modified levels of the alternative pathway.