Environmental Effects on Autumn Tree Color

1. Environmental Effects on Autumn Tree Color Presenter: Jim Loken Topic Advisor: Dr. Dale Herman http://www.treeplanter.com/images/trees/Maple/red%20maple%20rubrum/acre%20rubrum%20leaves.jpg

2. What do you already know? • “Tree leaves change color every fall” • “Leaves can have several different colors” • “The same tree might have different coloration depending on the year” • “Soil type can effect color change” • “Not all trees have the ability to change colors” • “It’s beautiful” • “Leaves are dying, pigments are changing” • “Fall is here” • “I’ve only noticed color change on deciduous trees”

3. Outline • Legend of Autumn Colors • The Role of the Sun • Pigments • Physiology of Autumn Colors • Lee and Tukey • Schaberg, Van Den Berg, Murakami, Shane, and Donnelly • Take Home Message

4. The Legend of Autumn Colors • Native American legend • The legend of Jack Frost http://www.hobbycraft.co.uk/LESSONS/pics/jackfrost.gif

5. The Role of the Sun • Radiation Energy • Electromagnetic spectrum • Visible light waves • Invisible waves http://praxis.pha.jhu.edu/pictures/emspec.gif

6. Pigments • Chlorophyll • Absorb red and blue light • Reflect green colors • Not stable, continually synthesized • Located in the chloroplasts • Imparts a “masking” effect • Carotenoids • Absorb blue-green and blue light (an accessory absorber) • Reflect yellow colors • Very stable • Located in the chloroplasts

7. Pigments • Tannins • Reflect brown color • Very stable • Located in the cell sap and cell walls • Most noticeably seen in dead tissue • Anthocyanins • Absorb blue, blue-green, and green light • Reflect red colors • Unstable • Sugar dependent • Accumulate in the vacuoles • Not found in all trees

8. Color Change:Main Environmental Factors • Average temperatures are lowering • Day lengths are decreasing

9. Color Change:Main Physiological Factors • Foliar sugar concentrations are increasing (especially important for red coloration) • Foliar nitrogen concentrations are decreasing

10. The storage of carbohydrates Seasonal Tree Carbohydrate Reserves Fall Winter Spring Summer Fall

11. The results of cooler temperatures and shorter days • Photosynthetic capacity declines • Chlorophyll production slows to a halt • Existing chlorophyll breaks down • Trees begin to store food • Lower temperatures limit phloem mobility of sugars • An abscission layer forms • Colors change Stoltenow, Sept 17, 2006

12. An abscission layer is formed • The xylem is still intact • Phloem tissues have been gradually severed • Remaining nutrients are trapped in the leaf Chaney, Oct 1994

13. Physiology of autumn colors • The abscission layertraps sugars and compounds called anthocyanidins in the leaf • Synthesis of anthocyanins is promoted • As the chlorophyll breaks down, the red colors are unmasked

14. Red color development • The shade of red an anthocyanin pigment provides is environmentally dependent • Anthocyanins are also influenced by pH • Low pH, acidic conditions promote red colors • As pH increases, these colors tend to get more purplish • Sugar and red maples, mountain ash, juneberries, and red oaks http://harvardforest.fas.harvard.edu/research/leaves/images/red_osier_ts.jpg

15. Anthocyanin:More than just a pretty pigment • Stress indicators • Antioxidant qualities • Osmotically active • “Light screen” http://www.grapes.msu.edu/images/coverConcord06.jpg

16. Yellow color development • The loss of chlorophyll allows the yellow, more stable carotenoids to shine through • Birches, cottonwoods, some elms, and some maples • Most trees turn yellow Copyright 2005 Martin Wierzbicki

17. Brown color development • Brown colors result from the presence of tannins • Tannins occur most commonly in dead tissue • As chlorophyll breaks down species with less carotenoids often display a brown to golden-brown color • Some oaks and beeches http://flyaway.smugmug.com/gallery/96774

18. Effect of Intermittent Mist on Development of Fall Color in Foliage of Euonymus alatus Sieb. ‘Compactus’ C.I. Lee and H.B. Tukey, Jr. J. Amer. Soc. Hort. Sci. 1971. 1:97-101

19. Misting Study #1 Objectives • “To determine the effect of rainfall on the development of red color, leaf abscission, and dormancy”

20. Mist 40 3-yr old Compact winged Euonymus plants from rooted cuttings Grown in greenhouse Misted for 20 s every 30 min during daylight Mist only applied to foliage Temp: 23-30 C (73-86 F) Control 40 3-yr old Compact winged Euonymus plants from rooted cuttings Grown in same greenhouse Same environmental conditions No Mist Methods(August) www.rgbonsai.com/burningbush.htm

21. 2 months later (October)… • 20 misted plants and 20 non-misted plants were transferred to a dry 15-25 C (59-77 F) room • Observations were recorded 4 months later (December)… • The remaining 20 misted plants and 20 non-misted plants were transferred to a dry 15-25 C (59-77 F) room • Observations were recorded

22. Red color developed in mid-Sept., and intensified with movement to the cooler room in Oct. By early Nov., leaves had abscised and plants were dormant Non-misted Control Observations

23. Misted for 2 months Leaves still green when moved to cool room in late Oct. No red color developed Leaves abscised by late Nov. Main plant was dormant by Dec. Misted for 4 months Leaves still green when moved to cool room in late Dec. Little red color development Leaves abscised in Jan. Main plant was dormant by Jan. Misted Plant Observations

24. Misting Study #2 Objectives • “to demonstrate the effect of rainfall on anthocyanin development and to elucidate the mechanisms involved”

25. Mist 40 Compact winged Euonymus plants grown from rooted cuttings Growth chamber 16 hr light periods at 16146 lumen/m2 (1500 ft-c) intensity Misted for 30 s every 30 min for 5 light hrs Mist only applied to foliage Temp: 24 C (75 F) day 18 C (64 F) night Control 40 Compact winged Euonymus plants grown from rooted cuttings Grown in same growth chamber Same environmental conditions No Mist Methods(12 week study)

26. Methods • After 8 weeks, both misted and non-misted plants were transferred to a cold room • Here they experienced 4 weeks in the cold room at 5 C (41 F) with 16 hr photoperiods of 2153 lumen/m2 (200 ft-c) intensity • The goal of this transfer was to enhance anthocyanin development

27. Methods • Levels of substances involved in anthocyanin synthesis were measured every 2 weeks from the leaves during the entire study including: • Anthocyanin • Total sugar • Protein N/soluble N ratio • Potassium

28. Anthocyanin & total sugar leaf content Lee and Tukey, 1971

29. N ratio & K leaf content Lee and Tukey, 1971

30. Leachate analysis • Leachates were collected at the end of every misting day • Done to clarify if lack of anthocyanin synthesis in misted plants is due to leaching • The leachate was analyzed to determine content • Similar substances to those found in the leachate were then reapplied to leaf samples

31. Leachate Content • Anthocyanin is derived from flavaniods via the shikimic acid pathway Lee and Tukey, 1971

32. Leachate Effects Control > Flavanol > Flavan > Lee and Tukey, 1971

33. Overall observations • Late season rainfall may inhibit fall color development due to the leaching of many substances necessary for anthocyanin synthesis

34. Factors Influencing Red Expression in Autumn Foliage of Sugar Maple Trees P.G. Schaberg, A.K. Van Den Berg, P.F. Murakami, J.B. Shane, J.R. Donnelly Tree Physiology. 2003. 23:325-333

35. Objectives • “To assess the environmental and physiological factors that influence the timing and extent of autumn red leaf coloration in sugar maples”

36. Methods • 16 trees were analyzed at a Vermont Research Station • Leaf samples were taken on 12 dates from June and October • Foliar Water content was measured • Foliar Carbohydrate levels were measured • Foliar Nitrogen levels were measured • Fall color was analyzed

37. Observations of Precursors to Anthocyanin Synthesis • Water levels were low compared to reported greenhouse grown sugar maples, but comparable to published levels for other native hardwoods • Carbohydrate concentrations were consistent with those reported for sugar maple • Nitrogen concentrations were much lower than reported averages

38. Foliar nitrogen concentration: August mean and seasonal averages Best published foliar N range = 16.000 - 23.200 g kg-1 This average = 13.478 g kg-1

39. Observations • The lower the foliar N, the earlier the red color expression, and the better the red color expression • Not all tree’s expressed red color at the same time

40. Fall color analysis Schaberg et al., 2003

41. Schaberg et al., 2003

42. Observations • Red color expression in trees may be a tree’s way of expressing nutrient deficiency • This may also explain why some trees in the study turned color before others http://images.google.com/images?q=sugar+maple&ndsp=20&svnum=10&hl=en&lr=&start=120&sa=N

43. Take Home Message The quality and extent of autumn color is affected by: • Late season rainfall (leaching and continued growth) • Lee and Tukey • Temperature • Day length • Nutrition (nitrogen) • Schaberg, Van Den Berg, Murakami, Shane, and Donnelly

44. What will the trees look like this year? • Wet spring • Dry summer • Average fall precipitation? • Nights have been getting cooler

45. It could be a good recipe for color, but… • What does the weather have in store? • How stressful was the summer? • Wind?

46. Best case scenario… • Warm days • Cool nights, but not freezing • Minimal precipitation Stoltenow, Sept 17, 2006

47. A Special Thanks to… • Dr. Dale Herman

48. Questions/Discussion??? http://images.google.com/images?q=sugar+maple+tree&ndsp=20&svnum=10&hl=en&lr=&start=160&sa=N