Soil salinity is a major concern to agriculture in arid and semiarid regions, where evapotranspiration causes salts originating from irrigation water (or sometimes naturally from the soil) to become concentrated in the rooting zone. In some areas, with good management, it has been economically feasible to ameliorate a sodic soil with Ca. The objective of this study was to investigate the effects of Ca amelioration of salinity (sodicity) on biomass, number of nodules, number of pods, weight of pods, ion uptake, and photosynthesis of Phaseolus vulgaris L. Pl ants were grown in one liter styrofoam pots under greenhouse conditions. In the first experiment, Na stress was accomplished by adding NaCl and Na2S04 at concentrations of 0, 20, 40, 60 , and 80 mmolcfl. The second and third experiments used concentrations of 0, 15, 30, 45, and 60 mmolc/1 NaCl or Na2S04 , combined with two levels of 15 and 30 rnrnolc/1 of either caso4 or cac12. Each styrofoam pot was irrigated with 300 ml of salt solution with a 0.25 leaching fraction on every fourth day for four weeks. Increasing Na concentration decreased biomass, number of nodules, number of pods, and weight of pods but increased ion uptake. Addition of NaCl in the substrate increased shoot Na, Ca, and Cl content, while Na2SO4 increased shoot S content. The photosynthesis rate was affected by all levels and types of sodium salts. Calcium sulfate treatments had a greater ameliorating effect than CaCL2 on Na induced salinity in snapbeans.

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 (P has eo lus vulgaris L. cv. Ear l iwax), 29 days from planting, were exposed to 0.0, 0.4, and 0.8 parts per million sulfur dioxide for 4 hours day-l 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 t he 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.