Academic journal article Michigan Academician

Botany & Plant Ecology

Academic journal article Michigan Academician

Botany & Plant Ecology

Article excerpt

Alterations in Soil Fertility by Autumn Olive May Temporarily Affect Native Shrubs. (Poster) Stephanie Rentschler, Chris Bouma, and David Dornbos, Calvin College

Autumn Olive is an invasive shrub reported to be capable of nitrogen fixation which likely contributes to Autumn Olive's competitive advantage. A previous study showed that after nine years, Black Walnut trees planted with Autumn Olive grew significantly taller and had significantly higher leaf chlorophyll content than those planted without Autumn Olive. To further evaluate the potential for Autumn Olive to increase the growth rate and leaf chlorophyll content of native plants, two year old Autumn Olive seedlings, exhibiting root nodulation, were planted with comparable Gray Dogwood, Black Cherry, Black Walnut, or Hawthorn seedlings in one gallon pots. Autumn Olive had substantially more leaves and higher leaf chlorophyll content than the native species seedlings. After six weeks, plants with Autumn Olive produced more leaves than the control plants. Additionally, the average chlorophyll content of native species was greater for those planted with Autumn Olive. These results suggest that nitrogen fixation by Autumn Olive provides increased nitrogen nutrition, a trait of particular value in poor soils, for proximal native plants. While Autumn Olive may provide some benefit to native shrubs, however, the faster growth of Autumn Olive will likely enable it to outcompete the nearby native plants in the long term.

Calvin College Tree Inventory Project. Scott Jones, Calvin College

Recent studies have identified multiple benefits to human health conveyed by the presence of trees. These, reports have particular relevance for college campuses such as Calvin College, which have a high density of people. Caring for campus trees and increasing their presence is one way to add to the quality of an educational experience and to help colleges become more sustainable. The Calvin Tree Inventory Project was begun this fall as a collaborative service-learning effort between a GIS class taught by Dr. Jason Van Horn and a Plant Taxonomy class taught by Dr. David Warners. Using hand-held Trimble GPS units, students inventoried and mapped over 3500 trees greater than 5 inches in diameter--all on the western side of Calvin's campus (our Ecosystem Preserve, which occupies the eastern half of Calvin's property, was not included). The collected data were then processed to create an interactive map. These data and map will he extremely useful in assessing sustainability implications of our campus landscaping practices, in formulating a tree replacement and maintenance plan, and in formulating meaningful research questions. This inventory is also an important component in our application to become a certified National Wildlife Federation Tree Campus, USA.

Changing the Density of the External Medium Changes the Gravitropic Response of Rice, Corn and Radish Roots. (Poster) Naila Kovacevic and Mark Staves, Grand Valley State University

The generally accepted model for plant gravity sensing invokes sedimenting, intracellular particles (statoliths) as the gravity sensors. However, statolith-free plant cells, tissues and organs respond to gravity. On the basis of experiment with single, non-statolith containing cells, we developed a new model for plant gravity sensing in which we suggest that the entire protoplast acts as the gravity sensor. In the gravitational pressure model, cells perceive gravity as a differential tension and compression at the top and bottom of the cell. We can distinguish between the statolith model and the gravitational pressure model by changing the density of the extracellular medium surrounding statolith-containing cells. The statolith model predicts that density of the external medium will have no effect on gravity sensing (since it will not affect the sedimenting of statoliths). The gravitational pressure model predicts that changing the density of the external medium will affect gravity sensing because it will change the relative buoyancy of the protoplast. …

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