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

MORPHOLOGY AND ANATOMY 21
The focus of this book is limited to cultivated barley, although it should be
recognized that wild barley with brittle rachis is harvested for food in certain
areas of the world, especially when famine is prevalent. To avoid grain loss
from shattering, wild barley is harvested prior to maturity while green and then
allowed to dry, thus preserving the kernel (Harlan 1978).
MORPHOLOGY AND ANATOMY
Growth and development begins with germination of the seed. Moral et al. (2002)
divided the growth and development of the barley plant into three major phases:
vegetative, reproductive, and grain filling. The vegetative phase begins at germination
followed by floral initiation characterized by early formation of tillers
and leaves. The reproductive phase begins with the formation of the spikelet
and ends with pollination of the ovaries in the spikelets. Grain filling begins
after pollination with enlargement of endosperm and embryo cell numbers for
accumulating dry matter and initial vegetative primorda, respectively. Duration
of each phase varies with genotype, geographic area, and agronomic and climatic
factors. The basic anatomical parts of the cultivated barley plant are roots, stems,
leaves, spikes, spikelets, and kernels (Figure 2.2), which are not unlike the parts
of most plants in the Poaceae family.
Roots
Upon absorption of moisture, germination occurs, initiating a series of events
beginning with the formation of roots. Roots of the barley plant are simple axial
structures having no leaflike organs, nodes, or internodes. Barley has two sets
of roots, the primary or seminal roots and the adventitious roots. Primary roots
are produced during germination arising from the coleorhiza, usually numbering
five to seven. These roots grow outward and downward, branching and forming
a fibrous mass, having hair roots for increasing surface area to maximize water
and nutrient absorption from the soil. Hair roots are short lived and are being
replaced continuously as the root system grows. Adventitious roots, arising out
of the crown as tillers develop, tend to be thicker and are less branched than
the primary roots. Seedling establishment begins with the downward extension
of roots into the soil. The extent of root development is dependent on the type
and depth of soil, availability of water and nutrients, and barley genotype.
Tillers
The coleoptile, a sheath enclosing tissue capable of mitosis, produces a “shoot”
that breaks through the testa or seed coat and grows up the dorsal side of the
kernel under the lemma shortly after roots begin to develop, providing further
stability to the seedling (Figure 2.3). The coleoptile encloses and protects the
shoot as it grows toward the soil surface. At this point a complex series of