secondarygrowth213-page8

secondarygrowth213-page8 - Pine wood: transverse section...

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Secondary Growth in Stems: Wood, Bark and Surface Features - 8 Radial longitudinal section (quarter-sawed timber) A radial section of wood will be cut along the radius of the stem. The long sides of vessels, fibers or tracheids will be visible. The sides of rays (note how rays stack up) will be visible as “streaks running at right angles across the lengthwise vessels and tracheids. A radial section of wood is cut parallel to the ray direction. In conifers one sees the “face” view of the conspicuous bordered pits of the tracheids. Tangential longitudinal section (plain-sawed timber) A tangential section of wood is cut perpendicular to the radius of the stem. Again, the long sides of vessels, fibers or tracheids will be visible. However, the rays will be seen in cross section, so you will see the ends of the rays.
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Unformatted text preview: Pine wood: transverse section radial section tangential section Growth Rings The cambium layers in woody secondary growth plants of temperate biomes have seasonal dormancy. Growth is most active in spring and tapers in summer, ceasing in fall. Spring (or early) wood typically has larger vessels that are more porous and fewer, smaller rays. Summer (or late) wood is comprised of denser, smaller cells with thicker walls. The first cells of the next seasons spring wood form are produced next to the smallest summer wood cells of the previous year. Annual growth rings are the result of the alternating pattern of spring and summer wood. Vessel size in spring and summer wood Section of Bristlecone Pine Wood 4240 4210 BC...
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