Gas exchange and carbon isotope composition of Ananas comosus in response to elevated CO2 and temperature

Abstract

Ananas comosus L. (Merr.) (pineapple) was grown at three day/night temperatures and 350 (ambient) and 700 (elevated) μmol mol-1 CO2 to examine the interactive effects of these factors on leaf gas exchange and stable carbon isotope discrimination (Δ,‰). All data were collected on the youngest mature leaf for 24 h every 6 weeks. CO2 uptake (mmol m-2 d-1) at ambient and elevated CO2, respectively, were 306 and 352 at 30/20 °C, 175 and 346 at 30/25 °C and 187 and 343 at 35/25 °C. CO2 enrichment enhanced CO2 uptake substantially in the day in all environments. Uptake at night at elevated CO2, relative to that at ambient CO2, was unchanged at 30/20 °C, but was 80% higher at 30/25 °C and 44% higher at 35/25 °C suggesting that phosphoenolpyruvate carboxylase was not CO2-saturated at ambient CO2 levels and a 25 °C night temperature. Photosynthetic water use efficiency (WUE) was higher at elevated than at ambient CO2. Leaf Δ-values were higher at elevated than at ambient CO2 due to relatively higher assimilation in the light. Leaf Δ was significantly and linearly related to the fraction of total CO2 assimilated at night. The data suggest that a simultaneous increase in CO2 level and temperature associated with global warming would enhance carbon assimilation, increase WUE, and reduce the temperature dependence of CO2 uptake by A. comosus.