Project Title

Comparison of photosynthetic rates for two evergreen, temperate species of different growth forms (tree versus herb)

Presenters

Academic department under which the project should be listed

CSM - Ecology, Evolution, and Organismal Biology

Faculty Sponsor Name

Paula C. Jackson

No humans or other animals were used

Abstract (300 words maximum)

We compared photosynthetic rates as determined through light response curves of two plant species with very different growth forms and different leaf anatomies. Magnolia sp. and Hexastylis sp. are both evergreen, temperate plants that grow in the Southeastern US. Magnolia grows as a tree, reaching up to ~37 meters high, whereas little brown jug (Hexastylis sp.) is an herbaceous plant, reaching only a few centimeters above the ground. Because of the differences in growth form, leaf anatomy, and ecological differences, we hypothesized that significant differences would exist in their overall light response curves and in the extent of the relationship between their maximum photosynthetic rates and temperature.

We worked on the Kennesaw State University, Kennesaw campus and all individuals selected were growing on a south-facing slope of a hill in the arboretum. We selected 10 individuals of each species and chose one south-facing leaf per individual. To determine light curves we used a portable photosynthesis system (Licor 6400), and measured changes in CO2 assimilation (μmolm-2s-1) with increasing light. We collected temperature data using an infra-red thermometer gun, and collected data on leaf temperature of individuals of each species as well as leaf litter temperature surrounding individuals of Hexastylis sp.

Contrary to our expectations, our preliminary data indicate that the small herb species Hexastylis sp presents a maximum photosynthetic rate that is almost double that of the tree species (Magnolia sp.). We continue to collect data on changes in maximum photosynthetic rate with changes in leaf temperature as the season progresses.

Project Type

Poster

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Comparison of photosynthetic rates for two evergreen, temperate species of different growth forms (tree versus herb)

We compared photosynthetic rates as determined through light response curves of two plant species with very different growth forms and different leaf anatomies. Magnolia sp. and Hexastylis sp. are both evergreen, temperate plants that grow in the Southeastern US. Magnolia grows as a tree, reaching up to ~37 meters high, whereas little brown jug (Hexastylis sp.) is an herbaceous plant, reaching only a few centimeters above the ground. Because of the differences in growth form, leaf anatomy, and ecological differences, we hypothesized that significant differences would exist in their overall light response curves and in the extent of the relationship between their maximum photosynthetic rates and temperature.

We worked on the Kennesaw State University, Kennesaw campus and all individuals selected were growing on a south-facing slope of a hill in the arboretum. We selected 10 individuals of each species and chose one south-facing leaf per individual. To determine light curves we used a portable photosynthesis system (Licor 6400), and measured changes in CO2 assimilation (μmolm-2s-1) with increasing light. We collected temperature data using an infra-red thermometer gun, and collected data on leaf temperature of individuals of each species as well as leaf litter temperature surrounding individuals of Hexastylis sp.

Contrary to our expectations, our preliminary data indicate that the small herb species Hexastylis sp presents a maximum photosynthetic rate that is almost double that of the tree species (Magnolia sp.). We continue to collect data on changes in maximum photosynthetic rate with changes in leaf temperature as the season progresses.