Photosynthesis &
Plant Responses to the
Environment
Associate Professor
Department of Biological Sciences
Central Washington University
Ellensburg, WA 98926-7537
email: poulsonm@cwu.edu
phone: 509-963-2808
fax: 509-963-2730
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Photosynthesis & Plant Responses to the Environment |
Mary
Poulson
Associate Professor Department of Biological Sciences Central Washington University Ellensburg, WA 98926-7537 email: poulsonm@cwu.edu phone: 509-963-2808 fax: 509-963-2730 |
Courses Currently Taught
BIOL 441 Plant Physiology
BIOL 111 Plant Biology
BIOL 110 Basic Biology
BIOL 200 Plants in the Modern World
| Plant Physiology is FUN!! | |
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Research Interests in the Poulson Laboratory
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The major goal of the research in my laboratory is to understand the mechanisms by which plants and algae alter their photosynthetic machinery in response to a changing environment. Photosynthetic organisms are exposed to fluxes in nutrient, water and light availability and must continually respond to these changes. This is especially true for photosynthetic mechanisms and there is still much to be learned about how photosynthesis is influenced by environmental changes. Some environmental conditions, such as high light intensity, low water availability and chilling temperatures can lead to the loss of photosynthetic productivity. We are interested in how woody and herbaceous plants and algae respond to such environmental stresses at the physiological, biochemical and molecular level. |
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Rivaling terrestrial giants on land,
the trees, brown macro-algae are masters of the inter-tidal region.
Bull kelp (Nereocystis luetkeana), is one of the most common Pacific
Northwest brown macro-algae. The light environment for Bull kelp changes
dramaticatlly as a function of ambient irradiance and tidal cycle. We
are interested in determing the extent to which Bull kelp experiences photoinhibition
and mechanisms by which the alga can protect itself from photoinhibition.
Andrew McNeil's MS research is an investigation of the ability
of Bull kelp to acclimate to variations in light exposure by measuring photochemical
efficiency or down-regulation, extent of photoinhibition, and pigment composition
across blades of the alga at different water depths after different light
exposures. It is hypothesized that since blades at higher depths receive
higher amounts of light energy, they will be able to downregulate more and
will better be able to recover from a photoinhibition. |
| Recently there has been a great deal
of progress in the elucidation of the regulation of plant responses to environmental
stimuli by gene expression. Much of this progress has been made by using
Arabidopsis thaliana. Due to is small size, however, the
usefulness of Arabidopsis for conducting nondestructive analyses of whole
plant growth and photosynthetic responses to environmental conditions has
been limited. This incongruity has lead to a gap between the knowledge
gained by molecular biologists versus the understanding of plant processes
in their natural habitats by plant physiological ecologists. In order
to bridge this gap, we have designed a novel system that allows nondestructive
measurement of photosynthesis for whole plants of Arabidopsis. |
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Thus far, the system has been used to investigate
the role of fatty acid unsaturation in photosynthesis using a triple mutant
of Arabidopsis that is devoid of trienoic fatty acids, and to show UV-B
radiation-enhanced tolerance of high light and drought stress for Douglas-fir
seedlings and Arabidopsis. These projects are examples of the importance
of combining molecular and physiological approaches for investigation of
the effect of specific genetic changes on plant responses to environmental stimuli. |
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The Douglas-fir project is aimed at finding ways to enhance survivorship rates for seedlings out-planted in reforestation efforts for clear-cut areas. We have shown that exposure to ambient doses of UV-B radiation induces morphological and physiological changes that lead to enhanced tolerance of high-light and water-stress for the seedlings. Ultimately we hope to determine growth and survivorship patterns for Douglas-fir seedlings grown under UV-B radiation and outplanted in the field. We are currently working to elucidate mechanisms for UV-B-induced environmental stress tolerance in Douglas-fir at the cellular and molecular level. To this end, we are developing protocols for the isolation of subcellular particles, including chloroplasts and thylakoid membranes from conifer species and investigatin identification and timing of production of UV-B absorbing compounds that protect Douglas-fir needles from UV-B radiation. |
| With Dr. M Regina Torres Boeger , Department of Botany, Sector de Ciências, Biologicas, Universidade Federal do Parana, Brazil, my laboratory working to determine effects of the environment on morphology and photosynthetic responses for the amphibious plant, Veronica anagallis-aquatica. We have also documented morphological and physiological responses of Arabidopsis thaliana to UV-B radiation. We have determined the UV-B radiation decreases stomatal density and stomatal conductance for Arabidopsis without affecting carbon assimilation rates. UV-B radiation also increases the capacity of Arabidopsis to down-regulate the efficiency of photosynthetic electron transport which helps to protect it from high light. UV-B radiation increases the content of the compatible osmolite, proline for Arabidopsos and this, in conjunction with lower stomatal conductance rates, leads to enhanced protection from drought stress in Arabidopsis grown with, as compared to without, UV-B radiation. | 
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Students in my Laboratory
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interested in working on any of these projects or other topics in plant
physiology are encouraged to contact Dr.
Poulson
and inquire about research opportunities in our laboratory. |
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Amy Berkley is working to determine whether synthesis
of dehydrins, a group of proteins known to protect plants against dehydration
stress, are produced in response to UV-B radiation in Arabidopsis. |
| Jessica Dellinger worked in my laboratory on a project in which
she found that Douglas-fir trees in the Pacific Northwest produce quantities
of UV-B absorbing compounds that correspond to ambient UV-B in the light enironment.
In addition Jessica us High Performance Liquid Chromatagraphy to identify
the composition of UV-B absorbing compound in Douglas-fir needles. Jessica
is now in Pharmacy school in Nevada. |
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Selected Publications
Poulson , ME , MRT Boeger and RA Donahue. 2006. Response of photosynthesis to high light and drought for Arabidopsis thaliana grown under a UV-B enhanced light regime. Photosynthesis Research, 90:79-90 Boeger MRT and Poulson
ME 2006 Effects of Ultraviolet-B radiation on leaf morphology of Arabidopsis
thaliana(L.) Heynh.(Brassicaceae). Acta bot. Bras. 20(2):329-338
Poulson, ME, G Samson and J Whitmarsh. (1995) Evidence that Cytochrome b559 Protects Photosystem II Against Photoinhibition. Biochemistry 34:10932-10938 Poulson, ME and EH DeLucia. (1993) Photosynthetic and Structural Acclimation to Light Direction in Vertical Leaves of Silphium terebinthinaceum . Oecologia 95:393-400 Poulson, ME and T Vogelmann. (1990) Epidermal Focussing and Effects Upon Photosynthetic Light-Harvesting in Leaves of Oxalis. Plant Cell Environ 13:803-811 |
last modified July, 2006, Mary E. Poulson