树木年轮-木材解剖学课件教程.ppt

Wood Anatomy of Tree Rings;Tree growth begins with photosynthesis to produce new wood when the growing season begins.;Trees grow upward and outward (including root tips), but…;Like “melting wax” !!;Meristems: apical and lateral growth;Meristems: annual growth can also be seen in the branching patterns of many tree species (esp. conifers);When we dissect the trunk, we can see this annual incremental growth, both upward and outward.;Locally Absent Rings;False Ring;Viewing wood: tangential, radial, and transverse planes. We are only interested in which of these?;Definitions:;Note the five major portions of the tree trunk.;Phloem (inner bark);Role of heartwood is…?;The Wood Cell: 1. Holocellulose a. alpha-cellulose (40-50%) = non-soluble = long-chain polymers (glucose) b. hemicellulose (20-35%) = readily soluble = short-chain polysaccharides 2. Lignin (15-35%) – non-carbohydrate materials in cell wall, very complex chemical structure. 3. Numerous Extractives – can be removed! a. tannins b. oils and resins c. other complex organic compounds ;Cell lumen;Wood Types; Coniferous Diffuse Porous Ring Porous;Conifers: radial files of cells (for most species);;Conifers: radial files of cells (for most species);Conifers: radial files of cells (for most species);Conifers: radial files of cells (for most species); Southern Pines Ponderosa Pine Red Pine; Eastern White Pine Western White Pine Sugar Pine; Balsam Fir White Fir Grand Fir;Wood Type 1: Conifer Wood;Wood Type 1: Conifer Wood;Wood Type 1: Conifer Wood;Ring porous: large earlywood vessels;;Ring porous: large earlywood vessels;Chestnut and Oak;Oaks rarely have missing rings but they can have very compressed growth.;Oak often exhibits an offset in the rings across rays.;Diffuse porous: small vessels throughout;Dif