Atmospheric CO2 concentration, N availability, and water status affect patterns of ergastic substance deposition in longleaf pine (Pinus palustris Mill.) foliage |
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Authors: | Seth Pritchard C Peterson G Brett Runion Stephen Prior Hugo Rogers |
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Institution: | (1) Department of Botany and Microbiology, 101 Rouse Life Sciences Building, Auburn University, AL 36849, USA, US;(2) School of Forestry, 108 M. White Smith Hall, Auburn University, AL 36849, USA, US;(3) USDA-ARS, National Soil Dynamics Laboratory, PO Box 3439, Auburn, AL 36831, USA, US |
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Abstract: | Leaf chemistry alterations due to increasing atmospheric CO2 will reflect plant physiological changes and impact ecosystem function. Longleaf pine was grown for 20 months at two levels
of atmospheric CO2 (720 and 365 μmol mol–1), two levels of soil N (4 g m–2 year–1 and 40 g m–2 year–1), and two soil moisture levels (– 0.5 and – 1.5 MPa) in open top chambers. After 20 months of exposure, needles were collected
and ergastic substances including starch grains and polyphenols were assessed using light microscopy, and calcium oxalate
crystals were assessed using light microscopy, scanning electron microscopy, and transmission electron microscopy. Polyphenol
content was also determined using the Folin-Denis assay and condensed tannins were estimated by precipitation with protein.
Evaluation of phenolic content histochemically was compared to results obtained using the Folin-Denis assay. Total leaf polyphenol
and condensed tannin content were increased by main effects of elevated CO2, low soil N and well-watered conditions. Elevated CO2 and low soil N decreased crystal deposition within needle phloem. Elevated CO2 had no effect on the percentage of cells within the mesophyll, endodermis, or transfusion tissue which contained visible
starch inclusions. With respect to starch accumulation in response to N stress, mesophyll > endodermis > transfusion tissue.
The opposite was true in the case of starch accumulation in response to main effects of water stress: mesophyll < endodermis
< transfusion tissue. These results indicate that N and water conditions significantly affect deposition of leaf ergastic
substances in longleaf pine, and that normal variability in leaf tissue quality resulting from gradients in soil resources
will be magnified under conditions of elevated CO2.
Received: 5 November 1996 / Accepted: 7 March 1997 |
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Keywords: | Pinus palustris Pinaceae Elevated CO2 Ergastic substances |
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