ISHS Acta Horticulturae 811: VI International Congress on Cactus Pear and Cochineal
MODELING OF TEMPERATURE AND RELATIVE HUMIDITY EFFECT ON RESPIRATION RATE OF NOPALITOS |
| Authors: | J.C. Guevara, L. Cedeño, E.M. Yahia, R.M. Beaudry |
| Keywords: | closed system, modified atmosphere, Opuntia ficus-indica |
| Abstract:
Respiration rate (RO2) of prickly pear cactus cladodes was measured as a function of temperature (T) at 5, 14, 20 and 25°C and at six relative humidity (RH) conditions between 65-90% (at intervals of 5%) for O2 partial pressures between 15 and 0.8 kPa, considering these conditions support aerobic respiration. The RO2 was determined by a closed system based on O2 depletion from the atmosphere in sealed containers containing 1 kg of cladodes. The O2 concentration decreased linearly over time and the slopes of the fitted lines were used to calculate the rate of O2 uptake. The rate of O2 uptake increased as temperature increased and decreased as RH increased. The RO2 at 5°C was approximately 30-40 times lower than at 25°C. The RO2 at 90% RH was between 30 and 90% lower than at 65% RH, depending on temperature. Data for lnRO2 for each RH level versus the inverse of the temperature (K-1) was submitted to a linear regression to determine Arrhenius constants and to calculate the apparent respiration Ea for the six RH conditions. The Ea was similar for each RH level, varying between a lower value of 113 to an upper value of 131 kJ mol–1. The following equation which describes respiration as a function of RH and T (°C) (r2 = 0.95) was developed: Ln(R) = (-0.1985+50.96 • (1/273.15+T) • RH) + (67.64–18430 • (1/273.15+T)) | |
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