Recovery from bud disappearance explains prolonged dormancy in Cleistes bifaria (Orchidaceae).

ABSTRACT

PREMISE OF THE STUDY Virtually nothing is known about what actually happens during prolonged dormancy, the period during which significant proportions of geophyte populations do not sprout after seasonal dormancy but remain alive underground, to emerge again 1 or more years later. This study investigated the fate of perennating buds on plants of the orchid Cleistes bifaria during prolonged dormancy, as well as effects of bud removal on dormancy and future sprouting. METHODS: Fates of healthy perennating buds were observed by examining underground plant structures over an annual cycle (fall, spring, fall). Effects of bud loss were assessed by removal of mature buds from one group of plants, followed by comparison with a control group a year later. KEY RESULTS: Of the 142 perennating buds under observation, 38% did not emerge in the spring, and all these were missing the buds that were present and healthy the previous fall. Removal of perennating buds in the fall did not affect whether a plant emerged in the spring; however, it reduced the number and size of perennating buds produced for the following year. CONCLUSIONS: For C. bifaria in West Virginia, prolonged dormancy appears to be the time period during which plants are recovering from the disappearance of perennating buds. Although the cause of bud loss remains unknown, research can now be focused on whether other species fail to emerge for the same reason, what causes buds to disappear, and why removal had no effect on spring emergence but negatively affected future sprouting.