Department of Biology

In my lab we are interested in the interaction between plant development and physiology in shaping plants’ responses to the environment (Watson et al. 1997, Huber et al. 1999, Watson & Lu 1999, ). Our primary focus has been on clonal plants, particularly the mayapple, Podophyllum peltatum where we have examined the role of the rhizome as a storage organ and how resource availability influences the timing and success of sexual reproduction (Geber et al. 1997a&b). We have shown that assimilate fixed at different times in the growing season is used differently by the rhizome system and that material stored in one year generally cannot be remobilized in the same year (in ms). We also have shown that the bud determination takes place over a two year period, but becomes fixed almost a full year before expression (Jones & Watson 2001), and have used this developmental timetable as a time line against which to understand how resources influence developmental pathway (in ms). Questions remain regarding the ability of stored assimilate to ‘save’ fruits, in the face of damage to the aerial shoots. Further studies would be welcome in this area.

A second line of research has examined mycorrhiza formation within clonal systems. We were the first to report the differential formation of mycorrhiza by different members of a rhizome system (in mayapple) and to demonstrate that the pattern of differential colonization is highly constant across environments and years (Watson et al. 2001). In recent work we have sought to understand the cause of this within-clone patterning, which seems to result from both internal plant controls and seasonal environmental variation (Ingram 2004, Ingram & Watson accepted). It would be interesting to manipulate mycorrhiza formation: induce them where they are normally not found and eliminate them from where they typically are, and monitor plant responses to these manipulations.

A new project involves the study of the differential fate of carbon obtained either via photosynthesis or carnivory in a number of carnivorous plants. We are particularly interested in facultatively carnivorous plants, like triggerplants, that are carnivorous only when flowering. These plants are also mycorrhizal, suggesting an interesting three-way competition for resources among growth, reproduction, and nutrient uptake. So far, this work has been done by undergraduates; it demonstrates that autotrophically fixed assimilate is used differently the heterotrohically-derived carbon. The strength of the differences is a function of the developmental status of the floral axis. These preliminary studies suggest that this relatively little-examined group of plants will prove to be interesting material for examining the interplay between resource allocation and development.

A third, seemingly unrelated theme of research in the lab concerns the determinants of species’ range limits. Tim Griffith, in a series of elegant experiments, demonstrated that edge populations of a weedy, photoperiodically sensitive species, Xanthium strumarium, are depleted for genetic variation relating to developmental timing, variation that could permit northward expansion of the species’ range (Griffith & Watson 2005, 2006). Currently, Marc Bogonovich, using large data sets and GIS techniques, is examining, on a continental scale, both physical and biological factors that affect species range limits in studies that include ferns, tomatoes and trees.