Barley for Food and Health: Science, Technology, and Products

SUMMARY 29
Barbs
Central Vein
Crease
Lateral Vein
Rachilla Hairs
Basal Marking
Rachilla
FIGURE 2.7 Barley kernel characters used for identification. (Courtesy of American
Malting Barley Association.)
about 13% of the kernel, the pericarp plus testa about 3%, the aleurone about 5%,
the starchy endosperm about 76%, and the embryo plus the scutellum about 3.0%
(Briggs 1978; Kent and Evers 1994). Barley kernels vary widely in size due to
genotype, position on the spike, and environmental growing conditions. Kernels
may weigh anywhere from 5 to 80 mg; however, most hulled barley kernels
will weigh between 35 and 45 mg, whereas typical hulless kernels will weigh
between 25 and 35 mg. Hulled and hulless kernels are shown in Figure 2.8. The
grain is said to be physiologically mature when dry matter accumulation ceases
(at about 40% moisture), but the kernel must dehydrate to 13 to 15% moisture to
reach harvest ripeness. During the dehydration phase, the pericarp is compressed
between the lemma and palea, which adhere to it on the outside and the testa,
which adheres to it on the inside in hulled cultivars.
For more detailed descriptions of the anatomy of the barley plant and kernel,
the reader is referred to the following publications: Åberg and Wiebe (1946),
Wiebe and Reid (1961), Briggs (1978), Reid and Wiebe (1978); Reid (1985);
and Kent and Evers (1994).
SUMMARY
Barley evolved over thousands of years from a wild plant to a domesticated
(cultivated) cereal grain. A major change from wildness to domestication occurred
with the expression of a tough rachis, preventing the seeds from scattering at
harvest ripeness. It can be surmised that this event was one of many natural
mutations that occurred over thousands of years. The morphological variability
seen in cultivated barley is ascribed to changes that occurred during cultivation