Gymnosperm Stem: Circular Bordered Pits in Pinus Wood
tangential section: Pinus stem
magnification: 400x
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 interrupted by short bands of horizontally oriented xylem rays. Xylem rays, usually one cell thick and a few cells high, are 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 a thicker, darker, inner torus.
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Gymnosperm Stem: Circular Bordered Pits in Pinus Wood
tangential section: Pinus stem
magnification: 400x
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 interrupted by short bands of horizontally oriented xylem rays. Xylem rays, usually one cell thick and a few cells high, are 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 a thicker, darker, inner torus.
Technical Questions:bioimagesoer@gmail.com