In the seeds of Chenopodium album L. visible phenomena preceding the final protrusion of the radicle enable a clear distinction between the induction and the progress of growth inside the covering structures. The light-dependent induction of radicle growth is not inhibited by exogenously applied abscisic acid (ABA). Experiments with 1-14C-ABA ruled out a lack of penetration of the hormone.
However, ABA does inhibit the growth of the radicle before final protrusion. This inhibition and the uptake of 1-14C-ABA are enhanced at lower pH values, indicating absorption of the undissociated molecule. The uptake of labeled hormone strongly increases during the growth of the radicle. This increase is not merely a reflection of extra water uptake.
Seeds of different degrees of dormancy contain equallly low levels of endogenous ABA. Much higher levels of ABA in the seeds were obtained by exogenous application of the hormone but these levels stills do not prevent the breaking the dormancy by light. It is concluded that ABA has no function in the regulation of dormancy in C. album seeds.