Carbon Dioxide Exchange and Acidity Levels in Detached Pineapple, Ananas comosus (L.), Merr., Leaves during the Day at Various Temperatures, Oxygen and Carbon Dioxide Concentrations

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Abstract
The effects of temperature, O2 and CO2 on titratable acid content and on CO2 exchange were measured in detached pineapple (A. comosus) leaves during the daily 15 h light period. Comparative measurements were made in air and in CO2 free air. Increasing the leaf temperature from 20 to 35.degree. C decreased the total CO2 uptake in air and slightly increased the total CO2 released into CO2-free air. Between 25.degree. and 35.degree. C, the activation energy for daily acid loss was near 12 kcal mol-1, but at lower temperatures the activation energy was much greater. Increasing O2 or decreasing the CO2 concentration decreased the total CO2 fixation in air, whereas the total CO2 released in CO2-free air was increased. The total acid content remained constant at 20.degree. C, but it decreased progressively with increasing temperature both in air and in CO2-free air. The total acid content at 30.degree. C remained constant in 2% O2 irrespective of CO2 concentration. The total acid content decreased in 21% and 50% O2 as the CO2 increased from 0-300. Apparently, photorespiration is present in pineapple. The lack of acid loss in 2% O2 suggest that light deacidification is dependent on respiration and that higher O2 concentrations are required to saturate deacidification.