Physiological Differentiation of Pistillate Flowers of Pecan and Cold Requirements for their Initiation1

Abstract

Abstract Histological examinations of forced buds of pecan [ Carya illinoensis (Wang.) K. Koch] from mature trees revealed a state of physiological differentiation of pistillate flowers by early August of the year preceding their initiation, thus predisposing them to form pistillate floral primordia. Low temperature exposure was required for pistillate flower initiation. This vernalization requirement was facultative for floral cone development, but absolute for floret formation, and was evident before the onset of rest. Grafting and in vitro bud culture techniques demonstrated that events associated with floral induction are separate from changes in the bud apex induced by cold exposure.