Maintenance of Normal or Supranormal Protein Accumulation in Developing Ovules of Glycine max L. Merr. during PEG-Induced Water Stress.

Protein accumulation in developing ovules of hydroponically grown soybean (Glycine max L. Merr.) plants was unaffected or enhanced by polyethylene glycol-induced water stress. The cultivar Wayne and the experimental variety ;9656' were severely stressed by inclusion of PEG-6000 in the nutrient solution to water potentials as low as -20 bar. Leaves rapidly yellowed and abscised under these conditions. Fresh and dry weight of ;Wayne' ovules was reduced by severe stress, but protein content was unaffected. Ovules of 9656 were more resistant to severe stress: fresh weight and dry weight were unaffected by stress and protein content increased. Moderately stressed Wayne ovules behaved like severely stressed 9656 ovules: seed fresh weight and dry weight were unaffected and protein content increased. However, protein content did not increase if the plants were defoliated. No changes in seed protein quality were observed with stress, based on polypeptide banding patterns after one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis.