02122naa a2200229 a 450000100080000000500110000800800410001910000220006024500830008226000090016552015320017465000160170665000170172265000170173965000160175665000090177265300210178165300120180270000180181470000190183277300410185110733121993-04-01       1989    bl ---       0--  u    #d1 aDORNBOS JR. D. L.  aDrought stress effects during seed fill on soybean seed germination and vigor.  c1989  aEnvironmental stress a substantial effect on leaflet productivity and yield, but its effect on germination and vigor is poorly understood. The objective of this study was to relate drought stress intensity during soybean[Glycine max (L.) Merr.] seed fill to reductions in seed yield, mass, germination and vigor. Drought was imposed on pot-grown plants (cv. Gnome) in the greenhouse by applying differing volumes of water during seed fill. Stress intensity was measured by summing stress degree days (SDD), the daily difference between the leaf and air temperature, measured using an infrared and shielded thermometer, respectively. As SDD values incresased from 46.2 to 141.2, leaf resistance increased 68% transpiration decreased 44% and apparent photosynthesisdecreased 71% verifying that severe drought had been imposed. Seed yield was linearly reduced 38 and 58% by drought in 1985 and 1986, primarily because few seeds were produced. Seed germination and vigor decreased as SDD increased. The effect of drought on germination and vigor was substantially less than that on yield and was inconsistent across years. Drought reduced standard germination percentage and seedling axis dry weight 5 and 12%, respectively and  increased single-seed conductivily 19%. Seed quality loss was correlated with reduced single-seed mass. Severe drought that occured throughout seed fill reduced yield and seed  number at a faster rate than seed mass, germination or vigor, and  maintained the development of at least some viable and ...  agermination  awater stress  aGerminação  aGlycine Max  aSoja  aEstresse hidrico  aSoybean1 aMULLEN, R. E.1 aSHIBLES, R. M.  tCrop Sciencegv.29, p.476-480, 1989.