Life Sciences Commons^™

Phenotypic Plasticity Of Reproduction In Schizachyrium Scoparium (Poaceae) Populations In Relation To Ecological History, Elizabeth M. Obee, James A. Quinn

Aliso: A Journal of Systematic and Floristic Botany

Genetic differentiation in reproduction in the wide-ranging Schizachyrium scoparium (Poaceae) has been demonstrated in uniform gardens. However, the fine-tuning of flowering phenology and biomass allocation in relation to spatial and temporal fluctuations in the local environment is best accomplished by plastic responses to local variability. An earlier central New Jersey study suggested that S. scoparium populations in old fields of 2 to 40 years differed in plasticity. To test this apparent effect of ecological history on the development of different levels of plasticity, genotypes were collected from high- and low-fertility sites in New Jersey (forest biome) and in Oklahoma (grassland …

Factors Limiting Sexual Reproduction In Platanus Wrightii In Southeastern Arizona, Jane H. Bock, Carl E. Bock

Aliso: A Journal of Systematic and Floristic Botany

Arizona sycamore (Platanus wrightii: Platanaceae) is a riparian tree of the southwestern United States and adjacent Mexico. It is failing to reproduce in certain canyons where mature, seed-producing trees of this species occur. Three hypotheses were tested to explain this reproductive failure: I) the presence of domestic cattle prevents reproduction, 2) seeds produced in certain canyons are inviable, and 3) annual flash floods destroy seedlings and young saplings but not the large, mature trees.

Canyons, either grazed or ungrazed by domestic animals, were surveyed for the presence of seedlings and young trees. In the laboratory, seeds were tested …