Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Responses of green ash (Fraxinus pennsylvanica Marsh.) and water oak (Quercus nigra L.) to anaerobic root environments were investigated. Initially, analytical methods pursuant to this objective were developed. An extraction solution containing DDT (dithio- threitol) and soluble polyvinylpyrrolidone proved best for oak ADH and protein recovery, while DTT and insoluble polyvinylpolypyroli- done were best for ash. A method for the control of the soil atmosphere surrounding intact roots was developed to study the effects of elevated CO(,2) in the anaerobic soil atmosphere of ash and oak seedlings. Ethanol, malate, ADH, ME (NADP-malic enzyme), CO(,2), and O(,2) within the root systems were monitored. Linear, statistically significant, increases in ADH and ME activities, and CO(,2) and ethanol concentrations were found in ash roots. The results suggested that CO(,2) may increase ME and ADH activities by lowering cytoplasmic pH. Increased soil CO(,2) resulted in higher levels of ethanol and CO(,2) in the roots of the oak than in those of the ash--an apparent expression of ash's superior flood tolerance. A long-term (9.5 month) flooding experiment was conducted in which the root gas composition, malate, soluble protein, ADH, selected root-coating constituents and their corresponding leaf concentrations, and growth were monitored on flooded ash and oak seedlings and drained controls. The ash maintained higher oxygen and lower CO(,2) concentrations during flooding than the less flood-tolerant species, water oak. This was reflected in differences in root coating composition, and the superior ability of the green ash to prevent the accumulation of potentially phytotoxic compounds in the leaves. A field study was conducted in which ash and oak seedlings were transplanted along four BLH (bottomland hardwood) transects that represented a wide range of soil-moisture, flooding regimes in Louisiana. Root coating constituents and ADH activity of green ash seedlings were assayed 1.5 years after transplanting. Oak mortality precluded analysis of this species. The deposition of root-coating materials and ADH activity were distinctly different enough from seedlings of the wet and mesic sites to be useful in the development of a two-group discriminant analysis function for site-wetness classification. The percentages of seedlings correctly grouped into the mesic and wet categories were 88.9 and 92.0, respectively.