Opportunities for geitonogamy in the clonal herb Maianthemum dilatatum

Clonal plant species have a diverse range of morphologies, which influences the spatial proximity of clonemates, which may affect the rate of geitonogamy. This study measured fine-scale clonal structure, pollinator behaviour, and impacts of geitonogamy on seed set in Maianthemum dilatatum (A. Wood) Nels. & J.F. Macbr., a herb with a spreading clonal morphology. Despite having a dispersive habit, on average more than 75% of the 10 nearest flowering neighbours of a ramet were clonemates of that ramet. Pollinators foraged preferentially among near-neighbours, but during bouts, visitors typically visited only two floral ramets, effectively lowering the expected contribution to geitonogamy based on flight distances alone. Experimental hand pollinations, pollinator exclusion, and emasculation treatments provided evidence that geitonogamy attributable to pollen from neighbouring ramets may reduce seed set in natural populations through a mechanism of self-interference. Even in a dispersive clonal plant species such as M. dilatatum, clonemate-level geitonogamy is a likely factor constraining female reproductive success.

Perception of neighbouring plants by rhizomes and roots: morphological manifestations of a clonal plant

A previous study showed that clonal morphology of the rhizomatous grass Elymus lanceolatus ssp. lanceolatus (Scibner & J.G. Smith Gould) was influenced more by neighbouring root systems than by the local distribution of nutrients. In this study we determine whether individual rhizomes or roots of E. lanceolatus perceive neighbouring root systems and how this is manifested in morphological responses of E. lanceolatus clones. Elymus lanceolatus was grown in the same bin with Pseudoroegneria spicata (Pursh) A. Love or Agropyron desertorum (Fisch. ex Link) Schult. plants. Elymus lanceolatus was separated from its neighbours by different barriers. The barriers allowed either only E. lanceolatus roots; only a single E. lanceolatus primary rhizome; or both roots and rhizomes to contact the neighbour root system. When only a single E. lanceolatus primary rhizome with potentially developing branching rhizomes made contact with the neighbour, the clonal structure of E. lanceolatus was modified more with P. spicata as the neighbour than with A. desertorum. With root contact of E. lanceolatus alone there was a similar effect with the neighbouring plants, but there was a more marked inhibitory effect on E. lanceolatus clonal growth with P. spicata than with A. desertorum, compared with the treatment with only a single rhizome in contact with the neighbour. Root resource competition in the unconstrained treatment (roots and rhizomes) between neighbouring plant and E. lanceolatus was more apparent with A. desertorum than with P. spicata. This study is one of the first to document that rhizome and root contact of a clonal plant with its neighbours may induce different clonal responses depending on the species of neighbour. Key words: Agropyron desertorum, clonal morphology, Elymus lanceolatus ssp. lanceolatus, plant interference, plant contact, Pseudoroegneria spicata, rhizome structure, root systems.

A quantitative assay for mouse granulocyte (CFU-g) and macrophage (CFU-m) precursors using plasma clots.

Cytochemical procedures were used to identify and quantitate granulocyte and macrophage precursors from mouse bone marrow cells in plasma clot cultures. Excellent clonal morphology and cellular enzyme activity were obtained when using plasma clots as the support matrix and buffered formalin acetone as the fixative. For cytochemical identification, naphthol AS acetate esterase staining was used for macrophages and peroxidase for granulocytes. These enzyme properties were confirmed by inactivation studies with a variety of inhibitors, group specific chemical modifications, and pinocytotic affinity for horseradish peroxidase. When mouse bone marrow cells (3 X 10(4) cells/dish) were cultured in plasma clots with human placental or L-cell-conditioned medium, 70 to 110 colonies were produced. Both pure granulocyte (CFU-g) and pure macrophage colonies (CFU-m) were observed, but approximately 5% of the total colony number was composed of mixed granulocyte/macrophage colonies (CFU-gm). The number of plated cells correlated strongly with the colony number (0.990 less than r less than 0.999).