Two cultivars of soybean (Glycine max [L.] Merr.) were grown in solution with up to 100 millimolar NaCl. Leaf solute potential was -1.1 to -1.2 megapascals in both cultivars without NaCl. At 100 millimolar NaCI leaf solute potential was -3.1 to -3.5 megapascals in Bragg and -1.7 megapascals in Ransom. The decrease in solute potential was essentially proportional to the concentration of NaCl. In both salt susceptible Bragg and salt semitolerant Ransom, leaf proline was no more than 0.4 micromole per gram fresh weight at or below 20 millimolar NaCI. At 40 and 60 millimolar NaCI, Bragg leaf proline levels were near 1.2 and 1.9 micromoles per gram fresh weight, respectively. Proline did not exceed 0.5 micromole per gram fresh weight in Ransom even at 100 millimolar NaCI. Proline accumulated in Bragg only after stress was severe enough to induce injury; therefore proline accumulation is not a sensitive indicator of salt stress in soybean plants.With the solute potential of a nutrient solution (about -0.07 MPa) being decreased nearly 0.05 MPa for each 10 mm increase in NaCI, leaves of plants growing in solutions with added NaCl would be expected to respond with lower solute potentials (6,10 soybean for up to 7 d exposure to one concentration (75 mM) of NaCl in solution culture. They also measured plant transpiration and the Cl-, Na', ABA, and cytokinin contents of plant parts.The present study was undertaken to clarify the relationships among salt tolerance, leaf solute potential, and the capacity to accumulate proline in two cultivars of soybean, salt sensitive Bragg and salt semitolerant Ransom. Our results will be compared with those of Roeb et al. Treatments. After 7 d in jars, salinity treatments were begun by adding NaCl to the basal nutrient solution. Three levels, 0, 10, and 100 mM constituted a first experiment. Stepwise additions were used to reach 100 mM with reduced osmotic shock. The first two steps were 10 mM d-'; others were 20 mm d-'. Each treatment was replicated six times. Plants were randomly distributed, with positions changed daily. The third (mature) and sixth (young) leaves, counting from the first trifoliate leaf, were harvested 14 d after beginning treatment. Because of results obtained, 0 and intermediate levels of 20, 40, and 60 mm NaCl were used in a second experiment. The only other difference was that all steps were 20 mM d-'. Plants were exposed to final levels of 10, 20, 40, 60, or

The effect of 0.0 (control), 0.1, 0.2, 0.4, and 0.6% of the hydrophilic polymer "Stockosorb K-400" hydrogel (HG) on survival and growth of buttonwood (Conocarpus erectus L.) seedlings grown in sandy soil under drought stress was investigated. The ability of the soil to retain water increased with increasing hydrogel concentrations. The highest level of the HG was capable of changing the typical sandy soil to a loam or even silty clay in terms of water potential and water content. The highest HG concentration prolonged the time of water loss from the soil by about 66% more than the control soil. During drought stress, the seedlings grown in 0.6% HG-mixed soil survived three times as long as those grown in the control soil. Shoot and root growth increased significantly in HG-amended soil as compared with non-amended soil. Plant water potential increased significantly with HG application, thus it aided in the establishment and growth of C. erectus seedlings under water stress conditions. There were no significant differences between 0.4% and 0.6%. The study indicated that an amendment of soil with 0.4% to 0.6% of the hydrophilic polymer "Stockosorb K-400" can be used in arid and semi-arid areas to enhance the drought tolerance of C. erectus seedlings.

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