Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Committee Chair(s)

William F. Campbell


William F. Campbell


The primary air pollutant sulfur dioxide has been shown to affect plant biochemistry and physiology, although very little is known about its effects on N2-fixation in legumes.

This study was designed to determine if N2-fixation, carbon partitioning , and productivity are affected under short term low level, so2 exposures.

Greenhouse grown snapbeans (Phaseolus vulgaris L. cv. Earliwax), 29 days from planting, were exposed to 0.0, 0.4, and 0.8 parts per million sulfur dioxide for 4 hours day-1 for 5 days in a fumigation chamber. At these concentrations there was no visible damage of the plant tissue and no significant changes in dry weight or yield components. Only the 0.8 parts per million sulfur dioxide treatment reduced acetylene reduction rates but rates returned to control levels with in 2 days after the removal of the stress. Sulfur dioxide treatment increased the total carbon -14 exported from the leaves of 0.4 parts per million sulfur dioxide treated plants while the 0.8 parts per million sulfur dioxide treated plants were found to retain more of their total carbon -1 4. This retention of carbon-14 at the 0.8 parts per million level may account for the inhibit ion of acetylene reduction due to lower photosynthate supplies arriving at the root - nodules.

These data suggest that low sulfur dioxide levels that would not cause any visible injury, may be interacting with carbohydrate assimilation and/or transport in P. vulgaris.