Changes in the Strength of Lettuce Endosperm during Germination

Abstract
The forces required to puncture intact lettuce (Lactuca sativa) seed and pericarp, endosperm and embryo were measured by the Instron Universal Testing Machine. It required about 0.6 N to puncture the endosperm in seeds imbibed in the dark at 6, 12 and 24 h. Endosperm of seeds imbibed in the light or in dark with GA required about 4.2 N at 6 and at 12 h and only about 0.15 N at 24 h. Forces required to puncture the embryo at all treatments and times remained constant at about 0.3 N. Changes in the strength of the endosperm do not appear to be related directly to protrusion of the radicle.