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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

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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


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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


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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


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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

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


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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


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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


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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


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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


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Misting Study #2 Objectives

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


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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)


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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


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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


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Anthocyanin & total sugar leaf content

Lee and Tukey, 1971


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N ratio & K leaf content

Lee and Tukey, 1971


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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


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Leachate Content

  • Anthocyanin is derived from flavaniods via the shikimic acid pathway

Lee and Tukey, 1971


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Leachate Effects

Control >

Flavanol >

Flavan >

Lee and Tukey, 1971


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Overall observations

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


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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


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Objectives

  • “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

  • 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

  • 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


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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


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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


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Fall color analysis

Schaberg et al., 2003


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Schaberg et al., 2003


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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


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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


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What will the trees look like this year?

  • 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…

  • What does the weather have in store?

  • How stressful was the summer?

  • Wind?


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Best case scenario…

  • Warm days

  • Cool nights, but not freezing

  • Minimal precipitation

Stoltenow, Sept 17, 2006


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A Special Thanks to…

  • Dr. Dale Herman


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Questions/Discussion???

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


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