Development of floral primordia and prediction of flowering in white oak (Quercus alba L.)

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Virginia Polytechnic Institute and State University

A two-part study was undertaken to gain a better understanding of oak floral development and flower crop variability as they relate to acorn crop variability. The first part traced the ontogeny of staminate and pistillate primordia of white oak (Quercus alba L.). It was found that staminate inflorescences are initiated in late spring and staminate flowers are structurally mature before the onset of dormancy in October. Pistillate inflorescences are not initiated until late summer, and pistillate flowers complete almost all of their development during the three weeks prior to anthesis. The second part of the study attempted to formulate predictive models for mature staminate and pistillate flower crop frequency distributions and densities by comparing the established phenology of floral differentiation with that of bud samples collected up to one month prior to flowering. It was found that the densities of staminate inflorescences (catkins), pistillate inflorescences (stalks) and total inflorescences are sufficiently predictable to make practical the use of linear models. However, because the pistillate inflorescence is so difficult to distinguish from the developing lateral bud, a large amount of error is generated in stalk counts completed one month before flowering. Also, the rapidity with which individual pistillate flowers are initiated just prior to pollination makes anticipation of their final number very difficult. The data suggests that although the year to year production of mature flower crops by a particular white oak may be consistent, it is not necessarily innate.