File:Herbaceous Dicot Stem Cortical Zones in Older Richinus (35917359500).jpg

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cross section: Richinus stem magnification: 100x

Like many herbaceous dicots, Richinus is capable of a small amount of secondary growth.

The epidermis in Richinus consists of a single layer of well cutinized cells.

The cortex is divided into two distinct zones; a large outer zone of thick walled collenchyma and a narrow inner zone of loosely packed parenchyma cells. The innermost area of the cortex is marked by a starch sheath or endodermis of tightly packed cells.

The outer layer of the stele is defined by a many layered pericycle of parenchyma cells interspaced with bundles of heavy walled supportive sclerenchyma cells.

Deep to the pericycle lies a ring of vascular bundles interspaced with medullary rays of parenchymal cells. In older stems the isolated vascular bundles are replaced with continuous rings of phloem, cambium and xylem, interspaced with medullary rays.

Xylem is endarch with protoxylem found towards center of stem and younger metaxylem towards the periphery of the stem. Phloem is endarch but modest annual growth makes it difficult to distinguish between the older protophloem at the periphery and younger metapholem to the center of the stem.

Early in development the most central aerenchyma of the pith breaks down leaving a large hollow central region.
Date
Source Herbaceous Dicot Stem: Cortical Zones in Older Richinus
Author Berkshire Community College Bioscience Image Library

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Creative Commons CC-Zero 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@N03/35917359500 (archive). It was reviewed on 23 June 2018 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-zero.

23 June 2018

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current00:01, 23 June 2018Thumbnail for version as of 00:01, 23 June 20183,264 × 1,840 (1.65 MB)Meisam (talk | contribs)Transferred from Flickr via #flickr2commons

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