This experiment was conducted to determine the effects of salinity (0, 0/03, 0/06, 0/08, 0/1 molar sodium chloride), seed size (small, medium, large), as well as their interactions on germination characteristics and seedling growth in soybean, Hill cultivar. The plots were arranged as factorial using a complete randomized block design of three replications. The study was conducted in Research Laboratory of College of Agriculture, Gorgan, in 2002. All characters under study, except germination uniformity were affected by seed size. Increase in seed size significantly increased germination percentages, germination rate, root length, stem length, seedling dry weight, total seed reserve depletion as well as conversion efficiency of seed reserves. Salinity affected all the traits adversely and significantly. The interactions of seed size and salinity significant in the germination rate, root length, seedling dry weight, and total seed reserve depletion as well as conversion efficiency of seed reserves. The value of salinity tolerance threshold indicated small seeds to be more tolerant than large ones. Germination uniformity and rate exhibited the least tolerance threshold while conversion efficiency in seed reserves demonstrated the most.
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