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

Abstract

Detached leaves were subjected to 15 combinations of temperature (20, 25, 30 and 35degC), O2 level (2, 21 and 50%) and CO2 level (0, 300 and 540 p.p.m.) both in air and in CO2-free air. Increasing the leaf temperature from 20deg and 35deg decreasedthe total CO2 uptake in air and slightly increased the total CO2 released into CO2-free air. Between 25deg and 35deg the activation energy for daily acid loss was near 12 kcal/mol, but at lower temperatures the activation energy was much greater. Increasing O2 or decreasing the CO2 concentration reduced the total CO2 fixation in air, whereas the total CO2 released in CO2- free air rose. The total acid content remained constant at 20deg but it decreased progressively with increasing temperature both in air and in 2% O2 irrespective of CO2 concentration. The total acid content fell in 21% and 50% O2 as the CO2 increased from 0 to 300 and to 540 ul/l. The data indicate that photorespiration is present in pineapple. The lack of acid loss in 2% O2 suggests that light deacidification is dependent upon respiration and that higher O2 concentrations are required to saturate deacidification