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Aquatic Monocot Stem: Dermal Tissues in Elodea

cross section: Elodea stem

common name water weed

magnification: 100x

 

Berkshire Community College Bioscience Image Library

 

Submerged hydrophytes like Elodea show numerous adaptations to an aquatic life. Notably there are no internal support tissues like collenchyma or sclerenchyma. The stem is entirely support by the water.

 

The epidermis is uniseriate and photosynthetic with a thin to non-existent cuticle and scattered stomata.

 

The bulk of the stem is occupied by a cortex that consists of a narrow outer zone of densely packed parenchyma cells and a large inner zone of aerenchyma with large radially arranged air pockets. The cells of the entire cortex contain abundant chloroplasts.

 

Vascular tissues are limited to the central stele and show no clear differentiation into xylem and phloem. In some specimens a single xylem vessel may be seen in the center of the stele.

 

A large air cavity occupies the center of the stele.

 

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Uploaded on October 11, 2017
Taken on February 10, 2014