Imbibition behavior of soybean (Glycine max (L.) Merrill) accessions with different testa characteristics

The imbibition behavior of 18 soybean accessions with a wide range of seed size and testa color was examined. In two accessions, the presence of an intact testa did not reduce the rate of water uptake, and provided no protection against imbibition damage. In one black-seeded accession, seeds soaked with the testa intact had a higher rate of water uptake than embryos without testas due to the loose adherence of the testa, hence creating a wide gap that allowed free water to be trapped between embryos and testa. In the other black-seeded accession, a delayed-permeability testa characteristic was associated with low levels of imbibition damage. Wetting and drying of seeds increased the rate of the water uptake, but this effect could not be attributed entirely to a loosening of the seed coat to the embryo due to the presence of ruptures in the testa surface. Although adherence of the testa to the embryo could play an important role in controlling water uptake in soybeans, it appeared to be difficult to measure or quantify its role per se.