Determination of the respiration rate of tomato fruit using flow analysis

A continuous-flow method using a conductometric detector was developed to measure CO2 resulting from respiration tomato fruit (Lycopersicon esculentum var. Santa Clara). The fruit are inserted into a 3.4-1 vessel and the atmosphere in the vessel continuously monitored for CO2, using a closed-loop system. The CO2 produced from fruit respiration diffuses through a Teflon (R) membrane, dissociates in the acceptor stream of deionized water, and the conductivity (mainly of H+ and HCO3-) is monitored. The conductance increase in the acceptor stream is proportional to the carbon dioxide concentration in the gaseous sample. Each determination is performed in 7 min, a time interval short enough to prevent respiration inhibition due to high levels of CO2 inside the respiration vessel. The relative error of measurement is - 3.0% (n = 7) for a CO2 level of 589 ppmv. Average respiration rates for the tomatoes var. Santa Clara of various stages of maturity ranged from 40 to 120 mg kg(-1) h(-1) evolved CO2. These results had low levels of variance between measurements, were consistent between repetitions, and were comparable with published data. (C) 2001 Elsevier Science B.V. All rights reserved.22324925

Stimulation of potato tuber respiration by cold stress is associated with an increased capacity of both plant uncoupling mitochondrial protein (PUMP) and alternative oxidase

The CO2 evolution of intact potato tubers (Solanum tuberosum, L., var. 'Bintje') was analyzed during a 10-day period of their warm (25+/-2degreesC) or cold (5+/-1degreesC) storage, to evaluate cold-stress effects on expression and activities of plant uncoupling mitochondrial protein (PUMP) and alternative oxidase (AOX). CO2 evolution rates were analyzed at 20degreesC, to reflect their possible capacities. The 20degreesC CO2 production declined from 13 to 8 mg kg(-1) h(-1) after 2 days of warm storage and then (after 3 to 7 days) decreased from 8 to 6.5 mg kg(-1) h(-1). In contrast, 20degreesC CO2 evolution did not change after the first day of cold storage, increased up to 14.5 mg kg(-1) h(-1) after 2 days, and decreased to about 12 mg kg(-1) h(-1) after 3 to 7 days of cold storage. Cold storage increased PUMP expression as detected by Western blots and led to elevated capacities of both PUMP (44%) and CN-resistant AOX (10 times), but not the cytochrome pathway. Since we found that cold storage led to about the same mitochondrial respiration of 40 nmol O-2 min(-1) mg(-1) attributable to each of the respective proteins, we conclude that both AOX and PUMP equally contribute to adaptation of potato tubers to cold.35321122