Plant cell walls (Ch. 15)

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• Plant cell walls (Ch. 15)
• 2. Dendrochronology

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Glucan chains may have 1000s to 10,000s of
glucose residues
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Some of the many compounds found in heartwood (of
giant sequoia). Many are not cell wall compounds.
Lamlom Savidge 2006.
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Cellulose microfibrils are synthesized at
plasmamembrane by particle rosettes that
include cellulose synthase.
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Cell wall matrix polysaccharides synthesized in
Golgi app and secreted to wall via membrane
vesicle.
Matrix polysaccharides Hemicelluloses xyloglucan
glucuronoarabinoxylans glucomannans
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Pectins are gel-forming polysaccharide components
of cell wall matrix
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Secondary walls contain lignin that displaces
water, binds cellulose, and prevents cell
expansion.
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Orientation of cellulose microfibrils determines
direction of cell expansion.
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Rate of cell expansion determined by cell wall
extensibility and turgor pressure
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Tree rings and dendrochronology
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Diffuse porous
Ring porous
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Tree rings for reconstructing pastclimateCO2
fertilizationinsect outbreaksfire
historyforest stand demography
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Tree rings record insect outbreaks. Pandora moth
on ponderosa pine.
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Tree rings and forest demographics
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