The maturation of microspores in the upper and lower florets of each maize spikelet follows a developmental pattern. There is a highly positive correlation between the two florets of the same spikelet such that the developmental stage of the upper floret can be predicted from the observed stage of the lower floret of the same spikelet by the use of the regression equation.

Microsporogenesis (MSG) (meiosis and pollen maturation) progressed at a faster rate in the upper floret than in the lower floret when the tassel was young, but not as rapidly as in the lower floret when the tassel was fully mature. Thus, the time interval separating the upper and lower florets of the same spikelet varies depending on tassel maturity.

The time intervals that separate the upper and lower florets of the same spikelet during MSG is longest with undomesticated Colombian varieties (5.3 days) and shortest in hybrids (3.0 days).

Sun-Yuan Hsu, Yih-Ching Huang and Peter A. Peterson

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