|Heagle, A - USDA-ARS|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 23, 1996
Publication Date: N/A
Technical Abstract: Increasing levels of atmospheric CO2 and O3 are affecting herbage growth over large geographic regions. Clones of white clover were selected that exhibited either resistance or sensitivity to O3 damage. These clones were then grown in chambers at 20, 70, and 100 nL/L-1 (ppb) O3 combined with 380 and 700 uL/L-1 (ppm) CO2. The sensitive clone had midrib vascular bundles with larger perimeters, cross sectional areas, and xylem cross sectional areas than the resistant clone. The resistant clone had thicker leaves (187 vs. 145 u) and contained more open space in 16 u cross selections (16.4 vs. 11.1%) based on image analysis. Enriched CO2 had little effect on the resistant clone but resulted in large decreases in the size of the vascular bundle of the sensitive clone. The resistant clone responded with decreases in the perimeter of the vascular bundle and cross sectional area in xylem at elevated O3. Additional research is needed to determine what role, if any, the modified anatomical geometry plays in adaptation to varying concentrations of atmospheric gases.