The R3 kernel displays yellow color on the outside, and the inner fluid is now milky white due to accumulating starch. Although initially slow to develop, the embryo is growing rapidly now and is easily seen upon dissection. Most of the R3 kernel has grown out from the surrounding cob materials and the silks at this time are brown and dry or becoming dry.

Figure 43 displays (from left to right) the R3 kernel (1) with surrounding materials, (2) intact as viewed from the opposite side from the embryo, (3) sliced longitudinally to reveal the front of the young embryo, and (4) sliced longitudinally through the center. Figure 44 shows sliced ears from (left to right) R3, R4 and R5 stages. 

Management Guides - R3 Stage - Milk

The kernels are now well into their rapid rate of dry matter accumulation, and are about 80 percent moisture. Cell divisions within the endosperm are essentially complete by R3, so growth is mostly due to cell expansion and filling of the cells with starch.

Final yield depends on the number of kernels that develop and the final size or weight of the kernels. Although not as severe as at R1, stress now can still have a profound effect on yield by reducing both of these factors. As the kernels mature, the amount of potential yield reduction from stress becomes less.

figure 42

figure 43

figure 44

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