Testa development in the caryopsis of Sorghum bicolor (L.) Moench

The development of the testa in type II and type III sorghums was documented with light, fluorescence and scanning electron microscopy. The testa developed from the inner integument. The inner integument had two layers, one of which was pigmented at anthesis. By 10 dpa (days past anthesis), the testa developed into two layers, the outermost layer contained pigments while the innermost was non-pigmented, but the walls contained ferulic acid. Pigmented material was deposited differently in the two sorghum types; type II developed vesicles in which the pigments were deposited, while type III deposited the pigments along the cell walls of the integument. The method of pigment deposition may reflect the difficulty in extraction of procyanidins (tannins) for nutraceutical use. It may be more efficient to extract tannins before physiological maturity. The testa was fully developed in both types of sorghum by 22 dpa. Pigmented materials appeared in the epicarp of type III sorghum at 26 dpa due to the action of the spreader gene. (C) 2003 Elsevier Ltd. All rights reserved.