HERMAPHRODITIC FLOWERING IN GAMBEL OAK

Gambel oak (Quercus gambelii Nutt.) is normally monoecious, flowering once a year in spring. In Utah, August 1978, several individuals were observed producing hermaphroditic flowers in riparian habitats. This unusual event was preceded by a general freeze of male catkins in May which resulted in low acorn production. In 1979 the same individuals flowered normally, with no evidence of freeze damage or hermaphroditic flowers being observed. Acorns were produced on these individuals in both years. It is suggested that hermaphroditic flowering in the Fagaceae is an ancestral condition, still present in the genome, but normally suppressed, which may be evoked by unusual environmental conditions. ON 2 August 1978, an unseasonal flush of flowering was discovered by R.P.N. and further observed by L.H.W. on several streamside clones of Gambel oak (Quercus gambelii Nutt.) near the mouth of Emigration Canyon near Salt Lake City, Utah, at 1,490 m elevation. This unusual phenomenon also was observed on streamside clones near Payson, Utah on 3 August at 1,460 m elevation. These inflorescences were unseasonal in that they had appeared late in summer (rather than in early spring) and had emerged from buds terminating twigs of the current season. Observations of these inflorescences were made during a general survey of Gambel oak in Utah to assess the impact of a spring freeze on acorn production. Oaks were examined in the range of habitats in which they occur (Neilson and Wullstein, 1980). On 9 August 1978, in situ examination of the inflorescences in Emigration Canyon by J.M.T. revealed an aberrant morphology similar to that described by Tucker (1972) for two species of oak occurring in California. The new flush appeared to consist of female inflorescences which were more elongated and bore many more flowers than normal. Most unusual of all, under a hand lens it was evident that some of the flowers in each inflorescence were hermaphroditic. We believe this is the first published report of this unusual event in Gambel oak. Although hybrids between Q. gambelii and Q. turbinella are known to occur in this area (Cottam, Tucker and Drobnick, 1959), all hermaphroditic I Received for publication 20 September 1979; revision accepted 23 April 1980. We thank Dr. Dov Koller of the University of Jerusalem at Rehovot for the suggestion of the bud removal experiment. flowers we observed occurred on clones judged not to be hybrid. In Q. gambelii normal female inflorescences are commonly 1 cm long or less (infrequently as much as 2 cm) and bear 1-4 flowers at anthesis, only 1 or 2 of these developing into mature acorns. As in the oaks generally, the female inflorescences are borne early in the growing season, in the axils of the upper leaves on young twigs of the current season (Turkel, Rebuck, and Grove, 1955). The male catkins, which appear in much greater numbers, emerge from lateral buds around the terminal bud or are borne at the base of the young elongating terminal shoot that will develop from the terminal bud. Although oaks generally flower in early spring, the flower buds are initiated the preceding year (Conrad, 1900; Turkel et al., 1955). In the shrubs observed in Emigration Canyon, the aberrant late summer inflorescences were borne in positions where next year's catkins are normally initiated, i.e. around the base of the new emerging shoot. Therefore, the aberrant inflorescences we observed in Emigration Canyon in August 1978 were initiated the same year, since they arose from buds terminating leafy twigs of this season. Thus their development, from initiation to anthesis, was compressed into a single season, a radical departure from the normal schedule of events. The inflorescence axes were stiff-not pendulous, as in male catkins-up to 3.2 cm in length and bore up to 14 flowers distributed more or less evenly along the length of the axis. Under a dissecting microscope, the flowers were seen to be mostly female but in each inflorescence at least a few flowers also contained stamens. On the longest inflorescence observed, the lowest four had the general appearance of female flowers (but each also con-