EXPERIMENTALLY-INDUCED CHANGES IN BUD FATES IN CERCIS-CANADENSIS L. (FABACEAE)

Stems of Cercis canadensis L. were pruned to three differently aged se gments at three different times during the summer of 1992 to determine the effects of treatment on bud fates (vegetative or reproductive). I n addition, the development of vegetative and reproductive buds was mi croscopically examined on untreated stems. In C. canadensis, multiple axillary buds are produced in a linear series at each code. The distal -most buds on the distal-most nodes become vegetative, and the remaini ng buds sequentially mature into reproductive buds over a 1-5-yr perio d. Microscopic buds elongate and become macroscopic in the summer prio r to maturing the next spring. The number of inflorescences that elong ated in 1992 was not affected by the pruning treatment, but of those, the number of inflorescences that aborted in 1993 increased with the n umber of nodes pruned. Deeper pruning thus reduced the number of matur e inflorescences per node. Some buds that would have normally develope d into reproductive shoots became vegetative shoots after stems were p runed. Microscopic observations of buds from nontreated stems indicate d that in all of the buds, initial leaf primordia had an orthodisticho us phyllotaxy, but in those buds that become inflorescences, the phyll otaxy changed to helical during floral initiation. Although a reversal in eventual bud fate occurred in pruned stems, phyllotaxy indicated t hat the buds are initiated in the vegetative state; therefore, a rever sion from the floral to the vegetative state did not occur. Intermedia te shoots produced on some experimental stems developed four foliage l eaves instead of four bracteose leaves, but the flowers on the inflore scence appeared normal.