1. Plant cell walls (Ch. 15)

2. Dendrochronology

Glucan chainsmay have 1000s to 10,000s of glucose residues

Some of the many compounds found in heartwood(of giant sequoia). Many are not cell wall compounds.

Lamlom & Savidge2006.

Cellulose microfibrils are synthesized at plasmamembraneby “particle rosettes” that includecellulose synthase.

Cell wall matrix polysaccharides synthesized in Golgi app and secreted to wall via membrane vesicle.

Matrix polysaccharidesHemicelluloses

xyloglucanglucuronoarabinoxylansglucomannans

Pectins are gel-formingpolysaccharide components of cell wall matrix

Secondary walls contain lignin that displaces water, binds cellulose, and prevents cell expansion.

Orientation of cellulose microfibrils determines direction of cell expansion.

Rate of cell expansion determined by cell wall extensibility and turgor pressure

Tree rings and dendrochronology

Diffuse porous Ring porous

Tree rings for reconstructing pastclimate

CO2 fertilizationinsect outbreaks

fire historyforest stand demography

Tree rings record insect outbreaks.Pandora moth on ponderosa pine.

Tree rings and forest demographics