By use of scanning electron and light microscopy a study on the histological organization controlling water entry in theCercis siliquastrumL. seeds was carried out. The intact mature dry seed ofCercisis impermeable. As we have previously demonstrated, this property is prevalently due to a non–cellular layer situated at the inner border of the testa enclosing the endosperm. When this layer is damaged, water enters endosperm and embryo, increasing their volume, and stretching the testa. The testa copes with the increasing volume of the seed without rupturing and decreases in thickness. The shape of the hypodermal cells changes from almost circular in section to periclinally elongated, as an effect of the imbibitio
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