Use all seed types at different stages. The embryo should be fine

Upon imbibition of dry seeds, metabolic events associated with germination

commence, even in those which are dormant.

Mobilization of the starch reserves in germinated cereal grains requires the production and secretion of a-amylase by the aleurone layer, which occurs in response to GA . Unlike the cells of the starchy endosperm, aleurone cells remain alive at maturity, but the ability to produce this enzyme is not normally acquired until the onset of maturation drying, but premature desiccation of wheat, barley, triticale and maize is able to induce its synthesis following germination.

The effect of drying is to increase the sensitivity of the aleurone layer to GA, which in barley provokes the expression of appropriate a-amylase genes (Amy1 and 2); these are not expressed in non-dried aleurone layers. Increased responsiveness to GA may be the result of desiccation-induced alterations to hormone receptors or signaling pathway components. It has been suggested that depletion of ABA (or a decline in sensitivity to ABA) in the aleurone layer due to drying increases the response of this tissue to GA. In maize, however, inhibition of ABA synthesis in the aleurone layer does not permit it to respond to GA without the imposition of a drying treatment.

Thus, one should seeds, not necessarily dormant, from imbibition till 5 to 10 days after germination.

Extracting the embryo is irrelevant, because the a-amylase expression is in the aleurone.

Amylase is an enzyme found in the germinating seeds. Imbibition process causes the release of growth plant (gibberelin) which stimulates the synthesis of amylase. Amylase activity is affected by many factors such as temperature, pH, enzyme concentration, substrate concentration, and the presence of any inhibitors or activators.