Colorado Blue Spruce (Picea pungens)

The sample

The sample I collected from the ground. Using some scissors, I scraped the side to be able to get a leaf.

I conducted this project as part of Professor Pringle’s EEB321 class at Princeton University.

With a Foldscope ready to use, I collected a sample of the first plant that caught my eye on a sunny day– a blue spruce. I always pass by this tree, knowing that it probably was put there by landscaping as decoration. Upon further research, I confirmed that this tree is not native to New Jersey, and is indeed mostly cultivated as an ornamental plant. I wondered how the cells of a leaf from this tree would differ from those of a tree with a more vibrant green color, and ‘regularly’ shaped leaves (which is to say, a non-needle leaf). The tree is located outside the dorms by Guyot Lane, so I went out there and found a piece of a branch on the ground right below it. It was in an area where there is not many other trees, and the ones that are there seem ornamental as well.

Observing

There was definitely difficulty in getting my sample in the Foldscope slide because of the thick needle shape. However, using scissors and shaving off parts of a single needle, I managed to place it in the viewer, with one side containing a mix of shavings of various shapes and sizes, and another a cross-section of the center of the sample.

Though the odd shape of the leaf samples made it difficult to position the lens, I managed to take a few pictures. From the way I prepared my sample, I suspect I observed the inner part of the pine needle in the two above images.

It was very nice to be able to see so many of the cells clustered in the sample. The color definitely mirrored the more subtle green, almost blue, color that this tree is known for. The shape was also not what I would expect in a flat leaf, which would be cells that are more spread out.

Cross-section of stem

Observing the cross section of the stem that held all the needles was difficult due to the thickness of the sample, but there were still some notable observations. The different layers in the stem were clearly defined, and the surrounding layer of green had a pattern of gaps in the tissue.

This species of tree was an interesting sight under a Foldscope. I believe it would have been even more revealing if I had more sophisticated shaving tools for preparing the sample. I am also now wondering whether this leaf cell arrangement is unique to the Blue Spruce. It would be interesting to me to see the different cell arrangements across flat leaves and needle leaves, and the patterns in their stems as well.

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