The ecophysiology of eastern dwarf mistletoe infection - Eastern dwarf mistletoe, a diminutive parasitic plant, can fell a mature white spruce in a matter of years. Curiously, a closely related host growing in the same forest stands, red spruce, tolerates infection and even succeeds in killing the parasite. Students, collaborators and I seek to determine the causal chain of events leading to white spruce mortality and contrast it against the mechanism of red spruce tolerance, drawing upon observations at scales from gene expression and hormone metabolism through whole–tree growth and stand dynamics. The host-parasite interactions we study are shaped by 19th century removal of red spruce/fir-dominated forests to create pastureland that was subsequently abandoned and recolonized by white spruce. We conduct this work at several sites along the Maine coast, including Monhegan Island.
The relationship between remotely sensed and leaf-level chlorophyll fluorescence emission - Chlorophyll, the green pigment in leaves responsible for absorbing light that powers photosynthesis, exhibits the unusual feature of re-emitting a small fraction of the light it absorbs (so-called fluorescence). Physiologists examining individual leaves have measured fluorescence for decades and have developed methods of using the strength of fluorescence emission to probe the inner workings of photosynthesis and leaf responses to environmental stress. Only recently, instruments capable of measuring chlorophyll fluorescence have been mounted on aircraft and satellites, allowing for remote sensing of whole landscapes. We partner with collaborators at Boston University and the University of Utah to understand how remotely sensed chlorophyll fluorescence might deepen our understanding of forests and their response to, for example, global climate change. [Some of this work is supported by a grant from the National Institute of Standards and Technology.]
The photoprotective role of anthocyanins - Anthocyanins, pigments responsible for the color of many red and purple plant organs (e.g., maple leaves in autumn) often accumulate in the upper layers of photosynthetic tissues during exposure to environmental stress and during juvenile and senescent stages of development. Using a combination of model systems (e.g., red- and green-leafed varieties of Coleus) and native plants (e.g., elderberry fruit-bearing stalks [peduncles]), students, collaborators at Victoria University of Wellington and I examine the hypothesis that anthocyanins screen light that would otherwise harm photosynthetic cells below.
Jaret Reblin, Laboratory Instructor in Biology, is a close collaborator on many aspects of these and other projects.