THE EMBRYO OF BARLEY IN RELATION TO MODIFICATION OF THE ENDOSPERM

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Abstract
Differential dissection of the embryo of barley grains, followed by observation of the extent of modification and assessment of α-amylase production in the endosperm, has shown that the various organs of the embryo make the following different contributions to modification. The isolated scutellum has a very limited ability to produce α-amylase and its powers of enzyme secretion are largely restricted to the peripheral region where aleurone cells are present. The stimulus which initiates enzyme formation in the aleurone is largely derived from the nodal region of the embryo, especially from the base of the node where subsidiary rootlets are formed; the scutellum apparently lacks the means of producing this stimulus. Translocation of the enzyme-inducing hormone from embryo to aleurone takes place through the apical half of the scutellum in which vascular tissue develops; this preferred route of translocation partially accounts for the asymmetric pattern of modification normally observed. Removal of the first foliar leaf from within the coleoptile allows increased production of α-amylase in the endosperm: this leaf can be regarded as a natural consumer of gibberellin.