Monocot Root: Smilax
cross section: Smilax root
common name: Greenbriar
magnification: 40x
Berkshire Community College Bioscience Image Library
The single layered epidermis lacks a cuticle. Root hairs appear as unicellular extensions of epidermal cells.
The cortex is well-developed and divided into two zones; a narrow outer layer of closely packed smaller parenchyma cells and a wide inner layer of open larger aerenchyma cells. In older stems, cortical tissues just beneath epidermis form a sclerenchymized exodermis. Scattered cortical cells may be sclerenchymized as well.
The inmost area of the cortex is bounded by a prominent endodermis of large U-shaped cells whose walls are heavily suberized, marking the Casparian strip. Within the endodermis occasional small passage cells serve to transport of water into the stele.
The stele is bound is a pericycle of several layers of thin walled parenchyma cells, often sclerenchymized in older roots.
The vascular tissues consist of radiating arms of xylem and phloem with phloem forming strands near the periphery of the vascular cylinder. The xylem is exarch: meaning the earlier smaller protoxylem is found towards the periphery and younger larger metaxylem to the center of the stem. Phloem tissues of sieve tubes, companion cells and phloem parenchyma are also exarch. The older protophloem is found towards the periphery and metaphloem towards the center of the stem. Phloem parenchyma may become sclerenchymized in older roots. Vascular cambium is absent, preventing secondary growth of the root.
The central of the stele is occupied by large pith containing thin walled starch containing parenchyma cells that may become sclerenchymized in older roots.
Technical Questions:bioimagesoer@gmail.com
Monocot Root: Smilax
cross section: Smilax root
common name: Greenbriar
magnification: 40x
Berkshire Community College Bioscience Image Library
The single layered epidermis lacks a cuticle. Root hairs appear as unicellular extensions of epidermal cells.
The cortex is well-developed and divided into two zones; a narrow outer layer of closely packed smaller parenchyma cells and a wide inner layer of open larger aerenchyma cells. In older stems, cortical tissues just beneath epidermis form a sclerenchymized exodermis. Scattered cortical cells may be sclerenchymized as well.
The inmost area of the cortex is bounded by a prominent endodermis of large U-shaped cells whose walls are heavily suberized, marking the Casparian strip. Within the endodermis occasional small passage cells serve to transport of water into the stele.
The stele is bound is a pericycle of several layers of thin walled parenchyma cells, often sclerenchymized in older roots.
The vascular tissues consist of radiating arms of xylem and phloem with phloem forming strands near the periphery of the vascular cylinder. The xylem is exarch: meaning the earlier smaller protoxylem is found towards the periphery and younger larger metaxylem to the center of the stem. Phloem tissues of sieve tubes, companion cells and phloem parenchyma are also exarch. The older protophloem is found towards the periphery and metaphloem towards the center of the stem. Phloem parenchyma may become sclerenchymized in older roots. Vascular cambium is absent, preventing secondary growth of the root.
The central of the stele is occupied by large pith containing thin walled starch containing parenchyma cells that may become sclerenchymized in older roots.
Technical Questions:bioimagesoer@gmail.com