Friday, January 2, 2015

Yonley's Bark

I know what you are thinking - what the heck is a Yonley?

Dave Yonley is one of my amazingly talented colleagues here at Eastfield College.  Dave is a videographer/film maker for the college and does truly outstanding work. (He even makes me look good!)

A few weeks ago Dave was on vacation in sunny Florida, walking around and taking in the sights - the ocean, the beaches, and the palm trees.

One of Yonley's photos from Florida
Dave came across a piece of bark that had fallen off a palm tree and decided to bring it back to Texas. He gave me some of it for my microscopes.

This is Dave Yonley.  He really doesn't like to be photographed, which is kind of ironic since he spends his work day filming other people, but I conned him into posing with his palm tree bark.
What caught Dave's eye was the pattern of the cellulose fibers that make up the bark.  Even in the picture above you can see at least two distinct layers of fibers produced at 90 degrees to each other. This makes the bark extremely strong.

This is the underside of the bark.  Note the wide strips - probably where it was attached to the tree, and the thinner fibers in different layers. [Camera image - taken outside]
Another view of the underside of the bark.  At first glance it looks like fabric, but unlike fabric, the fibers are not interwoven. [Camera image - taken outside.]
This image was taken with a dissecting microscope.  You can see that the flattened strips of bark also contain fibers.

Here is a look at the stringy fibers deeper in the bark.  
Scanning electron microscope view of the stringy fibers. Notice the wide range of sizes. [SEM image; 30x]
The diameter of a human hair is about 80 microns.  Here you can see that some of these fibers are smaller than a hair. [SEM image; 369x]  By the way, a micron, the unit on the image, is one-one millionth of a meter.
Scanning electron microscope view of the flat strips on the underside of the bark.  [SEM image; 218x]

In this image you can begin to see the cells that make up the structure of the bark.  [SEM image; 129x]
The cells to the left of the image divided in a flat plane.  To the right of the image is a fiber which, as you will see farther down, is formed by bundles of cells.  [SEM image; 450x]
Now, let's flip the bark over and take a look at the outer layer.

The top of the bark has an extra layer of fuzzy fibers.  

A closer view of the outer layer of fibers.  

Scanning electron microscope view of fuzzy fibers.  These look very much like the trichomes found on the leaves of many plants. [SEM image; 45x]
At this magnification you can see that these fibers are composed of strands of single cells, not bundles.  [SEM image;  [750x]
To show the composition of the palm tree bark, I cut a small section with a razor blade and then mounted it edge-on.

This edge-on view of palm tree bark is a composite of two pictures.  The fuzzy layer is at the top. Below that area several layers of fibers of different sizes laid down at right angles.  At the very bottom of the image is a flat layer.  [SEM image; 30x]
Cross-section of topmost fuzzy layer.  [SEM image; 50x]
Cross-section of fibers with fuzzy layer at the top of the image.  The red arrows indicate the single cells that make up the fuzzy layer.  [SEM image; 140x]

Cross section of a fiber showing the arrangement of individual cells.  The bundle is slightly flattened from being cut with a razor blade.  [SEM image; 300x]
What Dave found intriguing was the amazing strength of the sheet of bark collected from the palm tree, a strength resulting from many small, cellulose fibers being laid down in different directions. 

Natural, super-strong structures like this, the result of evolution and cell division, have obviously influenced the development of human-engineered materials including fabrics, ropes, and even steel cables.  Not bad for a palm tree.

The images in this blog are covered by a Creative Commons License.  They may be downloaded, used and/or modified for non-commercial purposes.
Murry Gans
Eastfield College
Mesquite, TX


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