File:Herbaceous Dicot Stem Collenchyma in Older Helianthus (35479351160).jpg
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Summary
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| Description |
cross section: Older stem: Helianthus magnification: 100x All vascular tissues in Helianthus are the product of primary growth. There are no signs of secondary growth (growth rings or lateral meristems) as might be seen in woody stems. Stomata may be seen in the single layered epidermis. Large multicellular trichomes are present and abundant in older stems. The cortex consists of an outermost hypodermis of 5 - 6 rows of collenchyma, a deeper layer of 5 -6 rows of parenchyma and a deepest band of endodermis (starch sheath). The stele is defined by a ring of vascular bundles separated from one another by medullary rays of parenchyma cells. Each vascular bundle consists of an outer supportive cap of sclerenchyma fibers (phloem fiber cap), a deeper layer of primary phloem with well defined sieve tubes and companion cells, and a deepest layer of primary xylem. In between the xylem and phloem, a narrow band of cambium my be seen. In some preparations the highly lignified cells walls of xylem and sclerenchyma are stained red orange. These cells are dead at maturity and can also be distinguished by a heavy cell wall and absence of cytoplasmic contents. |
| Date | |
| Source | Herbaceous Dicot Stem: Collenchyma in Older Helianthus |
| Author | Berkshire Community College Bioscience Image Library |
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This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication. |
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This image was originally posted to Flickr by bccoer at https://flickr.com/photos/146824358@N03/35479351160 (archive). It was reviewed on 23 June 2018 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-zero. |
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| current | 00:06, 23 June 2018 | | 3,264 × 1,840 (1.51 MB) | Meisam (talk | contribs) | Transferred from Flickr via #flickr2commons |
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