|Pritchard, S - AUBURN UNIVERSITY|
|Peterson, C - AUBURN UNIVERSITY|
|Rogers Jr, Hugo|
Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 13, 1996
Publication Date: N/A
Interpretive Summary: The response of forest species to increasing atmospheric CO2 are needed to predict probable changes which may occur in native forest systems. It is not known if the well documented increase in atmospheric CO2 level, in conjunction with limiting soil resources, will alter the internal leaf structure of longleaf pine. Disruption of chloroplast integrity was evident under elevated CO2, low soil nitrogen and water-stress. These results suggest that, in nature, longleaf pine may not benefit from elevated CO2, especially when soil resources are limiting, which may compromise the structure and function of the endangered longleaf pine ecosystem.
Technical Abstract: The response of forest species to increasing atmospheric CO2, particularly under resource limitations, will require study in order to predict probable changes which may occur at the plant, community, and ecosystem level. Longleaf pine (Pinus palustis Mill.) seedlings were grown for 20 months at two levels of CO2 (365 and 720 ppm) under two levels of soil nitrogen (40 or 400 kg N/ha/yr), and two levels of soil moisture (-0.5 and -1.5 Mpa xylem pressure potential). Leaf tissue was collected in the spring (12 months exposure) and fall (20 months exposure) and examined using transmission electron microscopy (TEM) and light microscopy. During early spring, elevated CO2 magnified effects of N and water treatment on starch accumulation, and in some cases contributed to altered organization of mesophyll chloroplasts. Disruption of chloroplast integrity was pronunced under elevated CO2, low N and water-stress. In fall, needles contained little starch; however, chloroplasts grown under high CO2 exhibited stress symptoms including increased plastoglobuli and shorter grana. A trend for reduced needle phloem cross sectional area resulting from fewer sieve cells was also observed under elevated CO2. These results suggest that, in nature, longleaf pine may not benefit from a doubling of CO2, especially when soil resources are limiting which may compromise the structure and function of the currently diminishing longleaf pine ecosystem.