Morphology and Reproduction

Maize is a tall, robust, monoecious annual with overlapping sheaths and broad, conspicuously distichous blades; staminate spikelets in numerous long spike-like racemes forming large spreading terminal panicles (tassels); pistillate inflorescence in the axils of the leaves, the spikelets in 8-16 (30) rows, on a thickened, almost woody axis (cob), the whole enclosed in numerous large foliaceous bracts or spathes, the long styles (silk) protruding from the summit as a mass of silky threads; grains at maturity greatly exceeding the glumes. Pollination, fertilization, and caryopsis development of maize follows a fairly standard pattern for chasmogamous wind-pollinated grasses, with the following points of exception and note:

• Pollen is produced entirely in the staminate inflorescences. Eggs are produced entirely in the pistillate inflorescences.

• Self-pollination and fertilization and cross-pollination and fertilization are usually possible, and frequencies of each are usually determined by physical proximity and other physical influences on pollen transfer. A number of complicating factors, such as genetic sterility factors and differential growth rates of pollen tubes, may also influence the frequencies of self-fertilization versus cross-fertilization.

• The "silk" on a developing ear is the style, a part of the female flower through which a pollen grain must travel; the styles on maize are the longest known in the plant kingdom.

• Shed pollen typically remains viable for 10 to 30 minutes, but may remain viable for much longer under refrigerated conditions.

• The staminate and pistillate inflorescences do not develop at the same time. The pistillate inflorescence is precocious. However, there is the appearance of slight rotandry because the elongating styles are delayed for about seven days in emergence from the bracts of the pistillate inflorescence, while the development of the later-developing staminate inflorescence is fully visible.

• The genetics of maize are better known than those of any other crop plant.

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