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| cross section of young stem at 25x showing cortex, fibers, phloem, and xylem. | cross section of young stem at 40x showing fibers, phloem and xylem. |
Result
Primary and secondary stems
There are multicellular trichomes on the epidermis of the primary stem. The stem has a square outshape. Beneath the epidermis, there is cortex that composed of parenchyma cells. Phloem and xylem surround by a ring of fibers. From the figures, the fibers and xylem stain blue with Toluidine blue. In the center of the stem, there is a board pith composed of parenchyma cells which contain a lot of starch grains.
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| cross section of young stem at 25x showing cortex, fibers, phloem, and xylem. | cross section of young stem at 40x showing fibers, phloem and xylem. |
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| cross section of young stem showing epidermis, cortex, fibers, phloem, and xylem. | cross section of young stem stained with Toluidine blue showing xylem, phloem, and fiber. |
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| cross section of old stem at 63x stained with IKI showing starch grains in the pith of the stem. | cross section of old stem at 50x showing xylem and starch grains stained with IKI. |
In the older stem, the xylem has a greater extension toward to cortex. The xylem cells near the pith are smaller. The vessel members become larger in the center of xylem. It is noticed that the bast fibers are denser and larger compare to the young stem. Both bast fibers and xylem stained red with Phloroglucinol. Rays are also observed which formed lines separating the vessel members in xylem.
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| cross section of old stem at 50x stained with IKI showing secondary xylem, secondary phloem, and rays. | cross section of old stem at 50x stained with Toluidine blue showing secondary xylem, secondary phloem, and bast fibers. |
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| cross section of old stem at 63x stained with Phloroglucinol-20%HCl, showing bast fibers, phloem and xylem. The vascular cambium presents between phloem and xylem. | cross section of old stem at 50x stained with phloroglucinol-20%HCl, showing xylem and phloem. |
Longitudinal section of a stem having secondary growth can reveal the development of xylem. The progression of helical thickenings: the helical (spiral), scalariform (ladder-like), and reticulate (net-like) can be observed in the following pictures.
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| longitudinal section of old stem at 63x showing A= pith, B and C = xylem. helical thickenings can be observed in region B. | longitudinal section of old stem at 63x stained with Phloroglucinol-20%HCl showing helical thickenings in the center. |
