Net CO₂ flux, light compensation points, and acclimation rates of selected foliage plants

Abstract

Net CO₂ flux of single leaves of different ages of Raphidophora aurea, Brassaia actinophylla, and Dieffenbachia amoena was measured using infrared gas analysis to determine the effect of leaf age on apparent photosynthesis, and to determine a "representative leaf" for further photosynthetic studies. In general, older leaves exhibited less net CO₂ uptake than younger leaves. However, high variability among leaves on the same plant made choosing a valid "representative leaf" for further photosynthetic studies improbable. Preliminary evidence indicates that R. aurea may exhibit C₄ or Kranz metabolism. Whole plant net CO₂ flux, light compensation points (LCP), acclimation rates and leaf diffusive resistances (LDR) were determined for Philodendron oxycardium, Raphidophora aurea, Brassaia actinophylla. Dracaena Sanderiana, Chamaedorea elegans, and and Peperomia obtusifolia. As a result of acclimation, all species exhibited increases in net CO₂ uptake and decreases in dark CO₂ evolution concomitantly indicating an increase in photosynthetic efficiency and a decrease in stored carbohydrate depletion. All species demonstrated from 2.9 to 7.8 fold total reduction in LCP during acclimation. P. oxycardium, R. aurea, B. actinophylla, and P. obtusifolia exhibited similarly rapid rates of acclimation, while D. Sanderiana and C. elegans acclimated much slower and had significantly higher LCPs. After 15 weeks of acclimation, LDR rates were significantly lower in P. obtusifolia than in all other species. Large variations in LDR existed within-species, with seed propagated B. actinophylla and C. elegans showing the greatest variability..