File:Woody Dicot Stem Pith Rays in Aristolochia (35878373866).jpg
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Summary
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| Description |
Cross section: Aristolochia stem Magnification: 40x Secondary growth in Aristolochia is characterized by an unusual fluted or bifurcated vascular bundles. Annular activity of the fascicular cambium produces typical collateral growth with large bands of xylem to the inside and smaller less extensive bands of phloem to the outside of the stem. The growing vascular bundles fail to fuse into continuous rings because of unusual activity of an intervascular cambium which produces annual growth of parenchyma cells to the inside and outside of the medullary rays. The continued expansion of the medullary rays, which extend from pith to cortex, pushes the vascular bundles further apart with each annual cycle, resulting in the characteristic fluting or bifurcation of the vascular bundles. Internal pressures exerted by annual growth of deeper tissues results in the rupture and tearing of the cortex, hypodermis and epidermis. The sclerenchyma band in the cortex becomes interrupted by cones of parenchymal cells with sclerids forming in areas of rupture and repair. The hypodermal collenchyma breaks down and is repaired with bands of parenchyma from the cortex. The epidermis is stretched and ruptures with patchy formation of corky tissues. Lenticels are formed in older stems. |
| Date | |
| Source | Woody Dicot Stem: Pith Rays in Aristolochia |
| 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@N03/35878373866 (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 (2.84 MB) | Meisam (talk | contribs) | Transferred from Flickr via #flickr2commons |
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