I’ve always thought apples have a unique texture. I don’t want to speak for everyone, but a good apple has some obligatory requirements: the skin needs to be good, the apple needs to be moist but also crisp, and it should never be mushy. I decided to examine on the microscope a small sample of an apple I enjoyed so that I could see what a good apple really looks like on a cellular level.

I had a relatively easy time setting this up; the apple slice was thin, so all I had to do was provide some lighting from the back and shift the controls to see what I want. I tried the method of putting the microscope on my phone, but it was immediately apparent this wouldn’t work out, so I went with the standard approach of putting my camera up against the viewing bit of the foldscope.

Here’s what I saw:

One thing I immediately noticed was how much moisture was in the structure of the apple. Furthermore, the whole thing seemed quite delicate; not so rigid and durable as other plant structures have seemed to me. This made me think about how impressive it actually is that the apple’s skin is so good at retaining moisture and protecting the insides from the elements.

More broadly, I wonder about fruit/plant skin as a protection and survival mechanism; what accounts for the vast differences between apple and banana and orange or lemon skins, for example? What evolutionary factors brought these differences about, and are they still necessary mechanisms in a post-agrarian world where many fruits we consume are manufactured in large spaces under controlled conditions? How does herbivory and predation play into this, and how do the organic and chemical composition of fruit skins vary across different ecologies? Alternatively, do fruit plants ever take the opposite approach, developing the fruit material itself to cope better rather than developing a protective skin? Are there durable fruits without skins, and what sort of evolutionary contexts are conducive to that outcome?

This post was made for Princeton’s EEB321 class by Nico Campbell.

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