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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 What do you already know? “Tree leaves change color every fall”

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Environmental effects on autumn tree color l.jpg

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


What do you already know l.jpg
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”


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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


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The Legend of Autumn Colors

  • Native American legend

  • The legend of Jack Frost

http://www.hobbycraft.co.uk/LESSONS/pics/jackfrost.gif


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The Role of the Sun

  • Radiation Energy

  • Electromagnetic

    spectrum

    • Visible light waves

    • Invisible waves

http://praxis.pha.jhu.edu/pictures/emspec.gif


Pigments l.jpg
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


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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


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Color Change:Main Environmental Factors

  • Average temperatures are lowering

  • Day lengths are decreasing


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Color Change:Main Physiological Factors

  • Foliar sugar concentrations are increasing (especially important for red coloration)

  • Foliar nitrogen concentrations are decreasing


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The storage of carbohydrates

Seasonal Tree Carbohydrate Reserves

Fall

Winter

Spring

Summer

Fall


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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


An abscission layer is formed l.jpg
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


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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


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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


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Anthocyanin:More than just a pretty pigment

  • Stress indicators

  • Antioxidant qualities

  • Osmotically active

  • “Light screen”

http://www.grapes.msu.edu/images/coverConcord06.jpg


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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


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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


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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


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Misting Study #1 Objectives Foliage of

  • “To determine the effect of rainfall on the development of red color, leaf abscission, and dormancy”


Methods august l.jpg

Mist Foliage of

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


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2 months later (October)… Foliage of

  • 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


Non misted control observations l.jpg

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


Misted plant observations l.jpg

Misted for 2 months movement to the cooler room in Oct.

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


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Misting Study #2 Objectives movement to the cooler room in Oct.

  • “to demonstrate the effect of rainfall on anthocyanin development and to elucidate the mechanisms involved”


Methods 12 week study l.jpg

Mist movement to the cooler room in Oct.

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)


Methods l.jpg
Methods movement to the cooler room in Oct.

  • 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


Methods27 l.jpg
Methods movement to the cooler room in Oct.

  • 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


Anthocyanin total sugar leaf content l.jpg
Anthocyanin & total sugar leaf content movement to the cooler room in Oct.

Lee and Tukey, 1971


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N ratio & K leaf content movement to the cooler room in Oct.

Lee and Tukey, 1971


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Leachate analysis movement to the cooler room in Oct.

  • 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


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Leachate Content movement to the cooler room in Oct.

  • Anthocyanin is derived from flavaniods via the shikimic acid pathway

Lee and Tukey, 1971


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Leachate Effects movement to the cooler room in Oct.

Control >

Flavanol >

Flavan >

Lee and Tukey, 1971


Overall observations l.jpg
Overall observations movement to the cooler room in Oct.

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


Factors influencing red expression in autumn foliage of sugar maple trees l.jpg

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


Objectives l.jpg
Objectives Sugar Maple Trees

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


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Methods Sugar Maple Trees

  • 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


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Observations of Precursors to Anthocyanin Synthesis Sugar Maple Trees

  • 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


Foliar nitrogen concentration august mean and seasonal averages l.jpg
Foliar nitrogen concentration: Sugar Maple TreesAugust mean and seasonal averages

Best published foliar N range = 16.000 - 23.200 g kg-1

This average = 13.478 g kg-1


Observations l.jpg
Observations Sugar Maple Trees

  • 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


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Fall color analysis Sugar Maple Trees

Schaberg et al., 2003


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Schaberg et al., 2003 Sugar Maple Trees


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Observations Sugar Maple Trees

  • 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


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Take Home Message Sugar Maple Trees

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


What will the trees look like this year l.jpg
What will the trees look like this year? Sugar Maple Trees

  • Wet spring

  • Dry summer

  • Average fall precipitation?

  • Nights have been getting cooler


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It could be a good recipe for color, but… Sugar Maple Trees

  • What does the weather have in store?

  • How stressful was the summer?

  • Wind?


Best case scenario l.jpg
Best case scenario… Sugar Maple Trees

  • Warm days

  • Cool nights, but not freezing

  • Minimal precipitation

Stoltenow, Sept 17, 2006


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A Special Thanks to… Sugar Maple Trees

  • Dr. Dale Herman


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Questions/Discussion??? Sugar Maple Trees

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


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