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The current corn growing stage in Champaign areas is R3, called the milky stage. After 18 – 20 days from the R1 stage, the kernels become mostly yellow and contain “milky” white fluid (i.e., starch accumulates). However, the moisture content of the kernel at R3 is around 80%.

Starch accumulation continuously occurs in the endosperm, and cell division of the endosperm is almost complete, indicating that the growth of kernels since R3 would be mostly due to cell expansion and starch accumulation, rather than cell division of the endosperm.

It also means that the potential kernel size would be finally determined at this stage. Severe environmental stresses would still be able to abort kernels, although not as easily as at the R2 stage. However, the effect of environmental stresses in R3 would be more relevant to shrinking kernels (due to moisture≈ 80%) rather than aborting kernels.

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