Gymnosperm Stem: Soft Wood in Pinus
radial section: Pinus stem
magnification: 40x
iron-alum hematoxylin and safranin stain
Berkshire Community College Bioscience Image Library
Gymnosperms like Pinus rely entirely on tracheids for water flow and mechanical support. True xylem vessels and wood parenchyma are lacking. While fibers are generally absent older stems may contain some fiber tracheids.
The uniform wood of Pinus consists almost entirely of longitudinally oriented bands of narrow, pale staining tracheids. Emerging at right angles are narrow xylem rays, one cell thick and a few cells high, and composed of clear, thin walled parenchyma cells. The lumen of many tracheids is crossed by branched trabeculae. Tracheid side walls contain large circular bordered pits that function to move water from tracheid to tracheid while preventing air flow from embolized tracheids. The membrane of each bordered pit is marked by a pale, thin, porous outer margo and thicker, darker, inner torus.
Also emerging at right angles are occasional large resin ducts, lined with living secretory parenchyma that produce resins and many toxic terpenes including turpentines.
Technical Questions:bioimagesoer@gmail.com
Gymnosperm Stem: Soft Wood in Pinus
radial section: Pinus stem
magnification: 40x
iron-alum hematoxylin and safranin stain
Berkshire Community College Bioscience Image Library
Gymnosperms like Pinus rely entirely on tracheids for water flow and mechanical support. True xylem vessels and wood parenchyma are lacking. While fibers are generally absent older stems may contain some fiber tracheids.
The uniform wood of Pinus consists almost entirely of longitudinally oriented bands of narrow, pale staining tracheids. Emerging at right angles are narrow xylem rays, one cell thick and a few cells high, and composed of clear, thin walled parenchyma cells. The lumen of many tracheids is crossed by branched trabeculae. Tracheid side walls contain large circular bordered pits that function to move water from tracheid to tracheid while preventing air flow from embolized tracheids. The membrane of each bordered pit is marked by a pale, thin, porous outer margo and thicker, darker, inner torus.
Also emerging at right angles are occasional large resin ducts, lined with living secretory parenchyma that produce resins and many toxic terpenes including turpentines.
Technical Questions:bioimagesoer@gmail.com