USE OF X-RAY-MICROANALYSIS TO STUDY HYDRATION PATTERNS IN BARLEY

Water uptake and redistribution by barley grains during steeping is important in determining malt quality. Previous methods have shown that water enters mainly via the embryo and moves more quickly along the ventral endosperm. These techniques lacked the resolution necessary to determine how water moves across the scutellum or the ventral furrow. A new technique is presented that locates areas of hydration either in starchy tissue, by exposure to iodine vapour, or in all tissues using MnCl2 as a tracer compound. Quantification of hydration is carried out with a scanning electron microscope by X-ray microanalysis, which measures levels of iodine, manganese or chlorine. Water first reached the endosperm after 2 h at 17 °C and moved most quickly along the ventral endosperm, setting up a diagonal penetration front. There was no passage of water through the ventral furrow but a small amount of water seemed to enter the distal end directly. In the initial stage of steeping there was greater hydration in the ventral endosperm compared with the dorsal, which may be related to a similar difference in the scutellar epithelium. © 1991, Academic Press Limited. All rights reserved.