The cupule and spatial accommodation of different kernel types

The surface area of the dry cob is reduced by shrinkage in relation to the size and induration of its cupules. The amount of cob shrinkage determines its capacity to carry various kernel types. If the mature dry kernels on the cob become either too tightly packed or too loosely spaced out, many of them will shatter during handling.

A rigid framework of large indurated cupules is coadaptive with broad flinty, floury or flinty-dent kernels because such cupules maintain adequate surface on the cob to accommodate the non-contracting kernels. In contrast, reduced or soft cupules are adaptive when cob shrinkage must coincide with kernel shrinkage in order to prevent shattering as follows: (1) sugary or other defective seed types that can wrinkle in concordance with rachis contraction; (2) long or indeterminate kernels such as occur in Shoepeg (Pepetilla) and certain pointed popcorns such as Confite Morocho that have spaced-out kernels that may become thin without wrinkling.

The type of kernel shattering referred to here is from the dead absorbing cells or so-called "black-eye" that occurs in most grasses and is not a normal means of seed dispersal via abscission layers.

Walton C. Galinat

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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