Woody Dicot Stem: Cork Development in Late One Year Quercus
cross section: One year Quercus stem
magnification: 400x
Berkshire Community College Bioscience Image Library
Quercus is noted for rapid cork formation. By the end of the first year the underlying activities of the cork cambium have replaced the epidermal and outer cortical tissues with a protective layer of cork rich periderm. The outermost layer of periderm consists of layers of cork cells, the phellem, which produce the waterproofing substance suberin. Cork cells are dead at maturity.
Deep to the phellem is a layer of living cork cambium or phellogen and just beneath that layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins.
In certain areas, the cork cambium over produces cork cells, resulting in the formation of ridges and deep cracks in the periderm. These deep fissures, or lenticels, permit gas exchange with tissues under the periderm.
Due to meristematic activity the vascular bundles have expanded to form a cylinder consisting of a narrow outer ring of primary phloem, a middle single layered ring of vascular cambium and a deeper large ring of primary xylem. The phloem is overlaid by heavy continuous ring of sclerenchyma.
Bulging into the pith are small masses of the first xylem consisting of small protoxylem cells overlaid by a few larger, heavier walled cells of metaxylem. Above this and extending to the cambium are columns of primary xylem divided by narrow rays, extending from the large parenchymatous pith to the phloem.
Technical Questions:bioimagesoer@gmail.com
Woody Dicot Stem: Cork Development in Late One Year Quercus
cross section: One year Quercus stem
magnification: 400x
Berkshire Community College Bioscience Image Library
Quercus is noted for rapid cork formation. By the end of the first year the underlying activities of the cork cambium have replaced the epidermal and outer cortical tissues with a protective layer of cork rich periderm. The outermost layer of periderm consists of layers of cork cells, the phellem, which produce the waterproofing substance suberin. Cork cells are dead at maturity.
Deep to the phellem is a layer of living cork cambium or phellogen and just beneath that layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins.
In certain areas, the cork cambium over produces cork cells, resulting in the formation of ridges and deep cracks in the periderm. These deep fissures, or lenticels, permit gas exchange with tissues under the periderm.
Due to meristematic activity the vascular bundles have expanded to form a cylinder consisting of a narrow outer ring of primary phloem, a middle single layered ring of vascular cambium and a deeper large ring of primary xylem. The phloem is overlaid by heavy continuous ring of sclerenchyma.
Bulging into the pith are small masses of the first xylem consisting of small protoxylem cells overlaid by a few larger, heavier walled cells of metaxylem. Above this and extending to the cambium are columns of primary xylem divided by narrow rays, extending from the large parenchymatous pith to the phloem.
Technical Questions:bioimagesoer@gmail.com