Document: DAV-3-34-16

Leaf respiration in sweetgum: Direct and indirect effects of elevated CO₂.

TISSUE, D.T.* ¹, J.D.LEWIS ², K.L.GRIFFIN ³ and O.R.ANDERSON ³

Texas Tech University, Lubbock, TX 79409 ¹
Fordham University, Armonk, NY 10504 ²
Columbia University, Palisades,NY 10964 ³

Abstract:
Trees exposed to elevated CO₂ generally show increased rates of photosynthesis and growth, but the effects of CO₂ enrichment on leaf dark respiration are more variable. Direct (short-term) effects of elevated CO₂ on respiration may occur when CO₂ is rapidly increased, resulting in changes in respiratory metabolism, including enzyme activity. Indirect (long-term) effects on respiration may occur after long-term growth at elevated CO₂ and are mediated through elevated CO₂ effects on leaf growth rate, nonstructural carbohydrate concentration, and tissue composition. In this study at Oak Ridge National Lab, sweetgum trees were grown in a FACE facility in ambient (36 Pa) and elevated (55 Pa) CO₂; measurements were taken using a LiCor 6400 (cuvette sealed with vacuum grease to minimize leaks) in the second growing season of fumigation. Direct CO₂ effects were observed as short-term increases in CO₂ reduced respiration by 14% (P<0.05), although this effect was fully reversible. Indirect CO₂ effects were also observed as dark respiration at growth CO₂ was reduced 14% on a leaf weight basis (P<0.01) and reduced 12% on a leaf area basis (P<0.1) in elevated CO₂. Despite reduced respiration, growth in elevated CO₂ increased the number of mitochondria by 140% (0.4 vs. 1.02 mitochondrion per 100 MICRO m²). Current research is focused on reconciling elevated CO₂ effects on respiratory metabolism, cell ultrastructure and rates of leaf respiration in field-grown trees.

Keywords: elevated CO@2@, respiration, FACE, sweetgum trees, mitochondria

This abstract is being presented at: 10:30 AM in session:
Poster Session #18: Elevated CO₂.