R2 kernels are white on the outside and resemble a blister in shape, figures 39 and 40. The endosperm and its now abundant inner fluid are clear in color and the tiny embryo can now be seen upon careful dissection. Although the embryo is still developing slowly at this time, the radicle, coleoptile, and first embryonic leaf have already formed. Thus, within the developing embryo is a developing miniature corn plant.

Much of the kernel has grown out from within the surrounding cob materials by R2 and the cob is close to or at full size. The silks. having completed their flowering function, are now darkening in color and beginning to dry out. The silk color is influenced by environmental conditions: hot, dry conditions cause darker silks.

Figure 40 displays (from left to right) the R2 kernel (1 ) with the surrounding materials, (2) intact as viewed from the opposite side from the embryo, (3) embryo side sliced longitudinally to reveal the front of the young embryo. and (4) sliced longitudinally through the center.

Figure 41 displays kernels from ears that were (from left to right) 7, 10, 12 (R2), and 18 (R3) days after silking. Each row then corresponds to the same manner of kernel display as in figure 40.

Management Guides - R2 Stage - Blister

Starch has just begun to accumulate in the watery endosperm and the kernels are beginning a period of rapid steady dry matter accumulation or seed-fill. This rapid kernel development will continue until close to R6. Although total plant nitrogen and phosphorus are still rapidly accumulating, relocation of these nutrients from vegetative to reproductive plant parts has begun.

The kernels are now about 85 percent moisture, and their moisture percentage will gradually decline from here until harvest. 

figure 39

figure 40

figure 41

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