Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 17, 2008
Publication Date: September 1, 2009
Citation: Fugate, K.K., Lafta, A.M. 2009. What Controls Respiration Rate in Stored Sugarbeet Roots [abstract]. Journal of Sugarbeet Research. 46(1&2):69. Technical Abstract: Although respiration is estimated to be responsible for 60 to 80% of the sucrose lost during storage, the mechanisms by which sugarbeet roots regulate their respiration rate are unknown. In plants, respiration rate is regulated by (1) available respiratory capacity, (2) cellular energy status, (3) or the availability of respiratory substrates. Previous research found no relationship between respiration rate, respiratory capacity (due to the combined capacity of the terminal oxidases of the electron transport pathway), and cellular energy status (measured as the ratio of ATP to ADP) in roots whose respiration rate was altered by abiotic stresses, suggesting that sugarbeet root respiration rate is not regulated by respiratory capacity or cellular energy status. Determination of tissue respiration rates in response to potential effectors of respiration demonstrated that respiratory capacity was 2.4-fold greater than that utilized by respiring root tissues and that respiration rate did not increase when respiration was uncoupled from energy production or when cellular ATP or ADP concentrations were altered. These results support the hypothesis that respiratory capacity and cellular energy status do not regulate sugarbeet root respiration and imply that sugarbeet root respiration is likely to be regulated by the availability of respiratory substrates. Respiratory substrates in sugarbeet root are synthesized from sucrose by the action of sucrose-degrading enzymes and the enzymes of glycolysis, the oxidative pentose phosphate pathway and the tricarboxylic acid cycle. To identify possible restrictions in these pathways that may limit the availability of respiratory substrates, compounds that are substrates, intermediates or cofactors of these pathways were profiled in roots whose respiration was altered by abiotic stresses.