Does Chlorophyll β Absorbency Change with Orientation to Sun in Aspen Bark That is the question by Tyler Streb Winter Ecology Spring 2016 CU Mountain Research Station Introduction Aspen ID: 762618
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Does Chlorophyll (β) Absorbency Change with Orientation to Sun in Aspen Bark? …That is the question, by Tyler Streb Winter Ecology Spring 2016 CU Mountain Research Station
Introduction:Aspen (Populus tremuloides) is the most widely distributed deciduous tree in North America ( Little 1971; Sargent 1890)Unique adaptations to survive harsh climates including photosynthetic bark in winter (Covington, 1975)Remarkable resilience after fire damage (Perala, 1991)Largest and Oldest living organism in the world is Pando(Mitton and Grant, 1996, Sussman , 2014) Covington, W. W. 1975. Forest Ecology and Management, 255(3), 797-802. Little , E. L., Jr. 1971. Atlas of United States trees: Vol. 1. Conifers and important hardwoods. U.S. Department of Agriculture, Forest Service, Miscellaneous Publication 1146, 9 p. +202 maps. Washington, DC . Perala , D. A. I. 1991. Renewing decadent aspen stands. In: Navrtil , S.; Chapman, P. B., eds. Aspen management for the 21st century. Symposium proceedings 1990 November 20-21; Edmonton, Alberta. Forest Canada, Northwest Region, North Forest, Central and Poplar Council: 77-82. Mitton, B. J.; Grant, M.C. 1996. Genetic variation and the natural history of quaking aspen. Bioscience. 46: 25-31. Sargent, C. S. 1890. The silva of North America. Volume 9. Cupuliferae – Salicaceae. Cambridge, MA: Arnold Arboretum, Harvard University. [Reprinted by Peter Smith, NY, 1947]. 190. Sussman , Rachel, Hans Ulrich. Obrist , and Carl Zimmer. The Oldest Living Things in the World . Chicago: U of Chicago, 2014. Print.
Photosynthetic organisms favor the energy yield via Chlorophylls α and β over other absorbent molecules (carotenoids, chlorophyll C, D etc.) Depends on…-Light availability-Physical Environment -Species -Chemical makeup of organism in question
Introduction: ContinuedChlorphyll α to β ratio increases with light exposure (Björkman et al, 1972)Chlorophyll β synthesis and distribution in Aspen Bark is key to understanding adaptions for winter survival Hypothesis: Absorbency and concentration of Chlorophyll Β increase with alignment to magnetic north Björkman O,Boardman N K,Anderson J M,Thorne S W,Goodchild D J,Pyliotis N A(1972) Carnegie Inst Washington Yearb 71:115–135.
Methods: The FieldThree ramets chosen at different elevations (3000m, 2900m, 2800m)Three mature trees chosen (at random) in middle of each1inchx1inch square of living bark tissue excised from magnetic north and south sides of trees Placed in labeled containers darknessRepeated
Methods: The LabCut-resized samples for consistency(1cmx1cmx1mm)Placed in 100% acetone for chemical extraction of chlorophyllImmersed in darkness for 3 days
Methods: ContinuedRan each of 18 samples through Bausch and Lomb Spectronic 20 (1953 model) Spectrophotometer at 646 nanometers and 662 nanometersUsing recorded absorbency data I calculated concentration of chlorophylls α and β from D.I. Arnon’s equation:Chlorophyll a (μg/ml) = 12.7 (A662) - 2.69 (A646) Chlorophyll b ( μg /ml) = 22.9 (A 646 ) - 4.68 (A 662 ) Total chlorophyll (μg/ml) = 20.2 (A646) + 8.02 (A 662 ) Arnon D. I. 1949. Copper EN2ymes in isolated chloroplasts. Polyphenoloridase in Beta vulgaris. Plant Physiology 24, 1-15.
Bausch & Lomb Spectronic 20 Colorimeter (title page verso) from Bausch & Lomb Spectronic 20 Colorimeter Cat No. 33-29-40, Reference manual. Rochester, New York: Bausch & Lomb Incorporated, [1962].
Machine required calibration of transmittance and absorbance between each reading Preliminary Data: Percent Absorbency β Absorbency (North) β Absorbency (South) α Absorbency (North) α Absorbency (South) 34 10 10 4 32 25 15 12 50 25 27 12 26 4 12 2 51 27 29 14 31 33 16 24 8 12 4 6 14 3 9 1 68 37 40 20
Initial Laboratory Methods: FailureAcetone of any concentration dissolves most plastics (like these cuvettes)
Would have been cool though…
Results: T-Test Mean Absorbency P-value: 0.003Mean absorbency in North Samples (34.88%), South (19.55%). P-Value of 0.003 indicates confidence rate of 99.7% in hypothesis.
ANOVA: Two factor (Sites .vs. North and South) P-value: 0.049 (North/South Between sites) ANOVA test showing correlation of orientation to sun (North .vs. South) and ramets of different altitudes. Considerable variation In 2800 meter site.
T-test: Mean Concentrations (North .vs. South) Average concentration of chlorophyll β in North samples (2.5 μ g/ml ) and south (1.5 μ g/ml ).
ANOVA: Two factor (Sites .vs. North and South) NS P-Value: 0.125Interaction P-value: 0.95 Visual correlation shows positive correlation with hypothesis between North and South Samples, p-value of 0.125 proves otherwise. Absolutely no positive relationship between two factors, 95% in favor of null. Notice variation in 2800 meter site.
Summary:Graphical and statistical analysis supports part I of hypothesis: Chlorophyll β absorbency increases with orientation to magnetic north. Confidence is 99.7%. Second aspect of hypothesis visually supported, but statistically insignificant with a P-value of 0.125. No correlation between North .vs. South factors and elevation.
Discussion:Absorbency of Chlorophyll β does indeed increase with orientation to magnetic north indicating highly efficient means of photosynthesis in dark winter months (178%) Although only half of my hypothesis was proven statistically, a larger sample size would have remedied this, especially considering large variability in 2800 meter site.Using an alternative method of pigment extraction (Ethanol or Methanol) might yield stronger results.Also given findings by Pearson & Lawrence in 1958, it might have been pertinent to analyze sample under wavelength in 440-450nm range for greater accuracy.With atmospheric CO2 and aerosol concentrations continuing to climb, solar diffusion in the visible spectrum and increased warming could affect the distribution of Aspen across North America Climate change may also affect seasonality and percentage of overall photosynthetic efficiency overwinter Drier conditions may or may not facilitate considerably stronger resiliency in Aspen as a result of fire disturbance
Acknowledgements:Thank you Derek Sweeney and Dr. Basey of the EBIO department for suppling lab equipment.Thank you Dr. Tim Kittel for your statistical assistance in Excel. Thank you Aspen specimens for your valuable tissue samples.Thank you University of Colorado for allowing us to use the property on Niwot Ridge at the research station.
References:Arnon D. I. 1949. Copper EN2ymes in isolated chloroplasts. Polyphenoloridase in Beta vulgaris. Plant Physiology 24, 1-15. Barr, M. Potter, L. 1974. Chlorophylis and Carotenoids in Aspen Bark (Populus tremuloides). The Southwestern Naturalist, Vol. 19, No. 2 pp. 147-154Beneragama, Ck , and K. Goto . 2010. Chlorophyll a : b Ratio Increases Under Low-light in 'Shade-tolerant' Euglena Gracilis. Tropical Agricultural Research Trop. Agric. Res. 22.1 Björkman O,Boardman N K,Anderson J M,Thorne S W,Goodchild D J,Pyliotis N A(1972) Carnegie Inst Washington Yearb 71:115–135. Covington , W. W. 1975. Forest Ecology and Management, 255(3), 797-802. Little, E. L., Jr. 1971. Atlas of United States trees: Vol. 1. Conifers and important hardwoods. U.S. Department of Agriculture, Forest Service, Miscellaneous Publication 1146, 9 p. +202 maps. Washington, DC. Perala , D. A. I. 1991. Renewing decadent aspen stands. In: Navrtil , S.; Chapman, P. B., eds. Aspen management for the 21st century. Symposium proceedings 1990 November 20-21; Edmonton, Alberta. Forest Canada, Northwest Region, North Forest, Central and Poplar Council: 77-82. Mitton, B. J.; Grant, M.C. 1996. Genetic variation and the natural history of quaking aspen. Bioscience. 46: 25-31. Sargent, C. S. 1890. The silva of North America. Volume 9. Cupuliferae – Salicaceae. Cambridge, MA: Arnold Arboretum, Harvard University. [Reprinted by Peter Smith, NY, 1947]. 190 . Pearson, L.C.. Lawrence, D.B. 1958. Photosynthesis in Aspen Bark. American Journal of Botany 45(5): 383-387. Sussman , Rachel, Hans Ulrich. Obrist , and Carl Zimmer. The Oldest Living Things in the World . Chicago: U of Chicago, 2014. Print . Shepperd , Wayne D.; Binkley, Dan; Bartos , Dale L.; Stohlgren , Thomas J.; Eskew , Lane G. 2000. comps. Sustaining aspen in western landscapes: Symposium proceedings; Grand Junction, CO. Proceedings RMRS-P-18. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 5-14. Title Slide Photograph by Taylor Kennedy, National Geographic. Pando Photograph Curtesy of Greenpeace.org.uk ( http://www.greenpeace.org.uk/blog/forests/9-awesome-facts-about-forests-20140321 )