Phosphorous in soybean [Glycine max (L.) Merr.] seed is stored primarily as phytic acid, which is nutritionally unavailable to nonruminant livestock. The objective of this study was to isolate mutations that reduce soybean seed phytic acid P and increase seed inorganic P. Following treatment with ethyl methanesulfonate, M2 through M6 plants were screened for high seed inorganic P. Seeds of M2 plants high in inorganic P produced progenies high in inorganic P through the M6 generation. M6 progenies of one plant averaged 6.84 g kg−1 seed phytic acid and inorganic P varied from 2.34 to 4.41 g kg−1 or 60 to 66% of phytic acid P plus inorganic P. M6 progenies of a second plant averaged 10.89 g kg−1 phytic acid and varied from 1.21 to 3.84 g kg−1 inorganic P, representing from 47 to 51% of the sum of phytic acid P plus inorganic P. In contrast, nonmutant seeds of the check cultivar Athow contained 15.33 g kg−1 phytic acid and averaged 0.74 g kg−1 inorganic P, representing 15% of the sum of phytic acid P plus inorganic P. Low phytic acid and high inorganic P in these progenies should increase the nutritional value of soy meal and reduce excess P in livestock manure.

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S U M M A R YFour soyabean cultivars were grown with two N application rates (50 and 300 kg N/ha) in the field at Hiroshima University, Japan, from June to August 1988. Cell membrane stability (CMS) by the polyethylene glycol (PEG) test, leaf water relations and nutrient concentrations in cell sap and leaf tissues were measured when the plants were 50 days old, in the uppermost fully expanded leaves.Cell membrane stability was higher at the higher N rate, the increase over the lower rate being greater in the cultivars Lee+ and Lee -than in Tamahomare and T201. Leaf water potential was not affected by the higher rate of N application. Osmotic adjustment, which was independent of water stress, was observed with the higher rate of N and it was higher in Lee + and Lee -than in Tamahomare and T201. It is suggested that osmotic potential in leaf tissues may influence CMS measured by the PEG test. Solute concentrations in cell sap and leaf tissues were higher at the higher N rate. Sugar and K were the major contributors to osmotic potential.

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Pairs of homozygous near-isogenic glycinebetaine-containing (Betl/Betl) and -deficient (betlhetl) F, lines of Zea mays L. (maize) were tested for differences in salt (1 50 mM NaCl or 127.25 mM NaCl plus 22.5 mM CaCI,) tolerance. The Betl/Betl lines exhibited less shoot growth inhibition (as measured by dry matter accumulation, leaf area expansion rate and/or, plant height extension rate) under salinized conditions in comparison to their nearisogenic betl/betl sister lines. These growth differences were associated with maintenance of a significantly higher leaf relative water content, a higher rate of carbon assimilation, and a greater turgor in Betl/Betl lines than in b e t l h e t l lines under salinized conditions. These results strongly suggest that a single gene conferring glycinebetaine accumulation (and/or a tightly linked locus) plays a key role in osmotic adjustment in maize. Yancey (1994) has recently discussed the roles of betaines and their sulfonio analogs as compatible solutes and in cell volume regulation. These solutes are excluded from the hydration sphere of proteins and tend to stabilize the tertiary structure of proteins (Yancey, 1994). They also prevent or reverse the disruption of the tertiary structure caused by noncompatible (perturbing) solutes such as urea (Bateman et al., 1992). It is probable that these compounds have similar functions in higher plants (Wyn Jones and Storey, 1981;Grumet and Hanson, 1986;Robinson and Jones, 1986; Rhodes and Hanson, 1993), but rigorous genetic experiments with higher plant mutants defective in betaine synthesis are needed to verify this point.Genetic tests for the role of glycinebetaine in osmotic stress resistance in Zea mays L. (maize) are now possible because of the development of a series of near-isogenic F, pairs of glycinebetaine-containing and glycinebetaine-deficient lines (Yang et al., 1995). Here we report the growth, water relations, gas-exchange characteristics, and solute compositions of these glycinebetaine-containing and gly-