Poster: Respiratory Pathways

Abs # 268: Induction of respiration by wounding is temperature dependent in sugarbeet (Beta vulgaris L.) root

Presenter:	Klotz, Karen L., klotzk@fargo.ars.usda.gov
Authors	Klotz, Karen L. (A)   Finger, Fernando L. (B)   Anderson, Marc D. (C)
Affiliations:	(A): USDA-ARS, Northern Crop Science Laboratory (B): Departamento de Fitotecnia, Universidade Federal de Vicosa (C): Department of Biological Sciences, North Dakota State University

The respiration rate of harvested plant products is largely influenced by temperature and wounding. In sugarbeet root, respiration rate is positively associated with storage temperature and the extent of wounding during the harvest and delivery of roots. An investigation into the underlying physiology of this phenomenon revealed that the wound induced increase in respiratory tissue activity was temperature dependent. Respiration was measured as O₂ consumption at 25^oC in tissue sections taken 1 cm below the root epidermis. Wounded roots incubated at 10^o C exhibited increased respiration over unwounded roots throughout thirteen days of incubation, with maximum respiration occurring two days after wounding. Wounding had no influence on respiratory activity at 1^o C. Determination of the capacities of cytochrome c oxidase and alternative oxidase respiratory pathways using isolated mitochondria and respiratory pathway specific inhibitors revealed a three to four-fold increase in cytochrome c oxidase capacity and a two to five-fold increase in alternative oxidase capacity at both 1^o and 10^o C. The data suggest that the lack of a respiratory wound response at 1^o was not due to a general reduction in metabolic activity or limiting mitochondrial respiratory capacity at the lower temperature. Similarly, an increase in phosphofructokinase activity in wounded roots was observed at 10^o, but not at 1^o C.