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Grain
Development Stages |
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Watery
Ripe Stage
During
the watery ripe stage, kernel length and width are established and the
kernel rapidly increases in size, but does not accumulate much dry matter
(Fig. 44-45). A clear fluid can be squeezed from the developing kernel.
The plant is green, but the lower leaves begin to die.
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Fig. 44. Watery ripe wheat kernel. |
Fig. 45. Watery ripe barley kernel. |
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Milk
Stage
During
the milk stage a white, milk-like
fluid can be squeezed from the developing kernel (Fig. 46-47). By the end
of milk stage the embryo is fully formed and about 1/32 inch in length.
During the course of this stage, nutrients stored in lower leaves are
redistributed to the upper plant, including the developing kernels,
causing several of the bottom leaves to die.
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Fig. 46. Milk stage wheat kernel |
Fig. 47. Milk stage barley kernel. |
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| Soft Dough
stage
The
water concentration of the kernel has decreased to the point where the
material pressed out of the kernel is no
longer a liquid but has the consistency of meal or dough (Fig. 48-51). The
kernel rapidly accumulates starch and nutrients and by the end of this
stage the green color begins to fade. Most of the kernel dry weight is
accumulated in this stage. In barley, the palea and lemma become firmly
adhered to the kernel. Once kernel water concentration decreases to about
75 percent, swathing of spring wheat can begin without reducing yield,
test weight, or protein level. |
Fig. 48. Soft dough wheat kernel. |
Fig. 49. Soft dough barley kernel. |
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Fig. 50. Soft dough wheat head. |
Fig. 51. Soft dough two row barley
head. |
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| Hard Dough Stage
The
kernel reaches physiological maturity at the end of this stage (Fig.
52-53). At physiological maturity, the glumes and peduncle are no longer
green and little green coloring remains in the plant. Kernel water
concentration decreases from a level of 40 to 30 percent. The main
reductions in yield beyond this stage result from harvest losses, and
environmental injuries, such as hail and sprouting. |
Fig. 52. Hard dough wheat kernel. |
Fig. 53. Hard dough barley
kernel. |
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Kernel
Hard Stage
The
plant has become completely yellow and the kernel has become firm (Fig. 54-55).
The kernel is difficult to physically divide by thumbnail but the surface
of the grain can be dented with the edge of the thumbnail. Kernel water
concentration is 20 to 25 percent. Unless drying facilities are available,
the crop must be swathed and windrowed at this stage because the grain
water concentration is too high for safe storage.
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Fig. 54. Kernel hard wheat kernel.
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Fig. 55. Kernel hard barley kernel.
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Harvest
Ripe Stage
The
plant has become dry and brittle and the kernel is hard (Fig. 56-58) The
kernel cannot be crushed between thumbnails and is difficult to dent its
surface with the edge of the thumbnail. If the kernel is crushed by other
means, it fragments. When the kernel water concentration has decreased to
13 to 14 percent the grain is ready for direct combining and storage.
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Fig. 56. Harvest ripe wheat kernel. |
Fig. 57. Harvest ripe barley kernel. |
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Fig. 58. Harvest ripe wheat, (left)
and two- and six row barley heads.
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| Dry
Matter Accumulation |
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| Dry matter accumulation in the
aerial parts of wheat and barley change with plant development stage (Fig.
59). From emergence to about the two-leaf stage, all of the aerial
dry matter is in leaves. From that stage forward, dry matter begins
accumulating rapidly in the stems. The developing head, which is initiated
at about the four-leaf stage, is regarded as part of the stem until
heading. By the flag leaf stage about 30 percent of the total aerial dry
matter is accumulated and it is almost equally distributed between leaves
and stems. About 55 percent of the total aerial dry matter is accumulated
by the time the heads are completely emerged. Dry matter accumulation in
the stems declines after heading and all additional dry matter is
accumulated in the kernels. By kernel hard stage dry matter is distributed
essentially between stems and heads. |
Fig. 59. Dry matter accumulation in a
cereal grain plant.
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