The Structure and Ontogeny of the Hilum Region in Sorghum bicolor

Abstract

The 'black layer' or 'dark layer' in the grains of Sorghum bicolor (CK60 x TX415) can be seen 15 days after pollination and was identified by selective staining as being due to phenolic deposits within the phloem parenchyma cells. These deposits did not stain positively as tannins with the vanillin- hydrochloric acid reagent. The phloem parenchyma cells became blocked with mucilage and pectic compounds at maturity, forming the closing layer of the hilum, causing the seed to dry out and the black layer to become more distinct. The ontogeny and structure of the black layer in S. bicolor is discussed with reference to that of maize.