Date of Award

Spring 1998

Project Type

Dissertation

Program or Major

Plant Biology

Degree Name

Doctor of Philosophy

First Advisor

Thomas Lee

Abstract

Canada mayflower (Maianthemum canadense var. canadense Desf.), a rhizomatous perennial herb, was the subject of field experiments investigating the role of several factors on the sexual reproduction of ramets. Mayflower ramets may be either flowering (with 2-3 leaves and a terminal inflorescence consisting of 4-35 perfect flowers) or vegetative (1 leaf).

Pollen addition increased the number of seeds matured by ramets in three out of four years in which pollen level was experimentally manipulated. The lack of compatible pollen is thought to be a major factor limiting seed maturation by ramets.

The act of severing the rhizomes, such that ramets were isolated from the rest of the genet, also limited the number of seeds matured by ramets, but only when pollen was not limiting. In addition, rhizome severing was responsible for a reduction of, on average, 3.2 flowers brought to anthesis per ramet. Rhizome severing did not appear to delay flowering or to decrease the length of time that flowers were receptive to pollen. Rhizome severing also resulted in increased initiation of rhizomes, while the level of pollination (open pollinated, overpollinated, bagged, and vegetative) was independent of rhizome initiation.

The number of seeds matured per ramet was negatively correlated with the mean weight of seeds, indicating that individual ramets were to some extent resource limited with few-seeded ramets maturing heavier seeds than ramets bearing many seeds. There was no difference detected in the mean number of seeds matured by overpollinated ramets flowering for the first and second time.

The number of seeds matured per ramet was related to the identity of the ramet directly acropetal and basipetal on the same rhizome system ("context"). The most common context was also the one with the lowest seed maturation (no ramet or a dead ramet both acropetal and basipetal). Flowering ramets were older than vegetative ramets and differed in their contexts. Ages also differed with context and permitted a first attempt at inferring ramet and genet development.

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