How Large Are Plant Cells? (BioE80 Spr 2015)

How big are cells in the plants that grow around us? Luckily, our Foldscope can help!

 

I first started by taking an image of a flower that was growing outside the classroom:

IMG_1109

 

With the magnification provided by the Foldscope, we can see that there are little rectangular cells that make up this flower. So, how would we go about finding the size of these cells?

 

To get an idea of how big these cells are, we need something that we know the size of: printed paper! Printers don’t print in continuous amounts. Instead, they print with a resolution given in dots per inch (DPI). This means that if we can see how big a dot of ink is in our Foldscope, we can get an idea of how big these cells are! The average printer is 300 DPI, and I took this image of ink:

IMG_1136

 

Let’s do a little math to see how big these dots are: with 300 dots per inch, and 2.54 centimeters per inch, then each dot is 1/300 *  2.54 = .0084 centimeters or 84 microns.

Let’s overlay the two images:

Capture

 

We see that about two average cells fit lengthwise and width-wise, which gives us 84 /2 = 42 microns in approximate size for the cell.

EDIT: Thanks to Prof. Prakash’s suggestion below, we can use the 100 micron dot on our slide covers:

IMG_1139

We see that we can actually fit 5 average cells lengthwise and 12 for the width. That gives us 100 /5 or 20 microns length and 100 / 12 or 8 microns width.

Capture 2

Bonus: can you estimate the size of these?

IMG_1123

Contributor: Rahul Prabala

 

2 Comments Add yours

  1. Manu Prakash says:

    @Rahul: excellent idea; but I think you are overestimating the length. The cells might be smaller than you estimate. The DPI is a complex number; and I would trust thickness of a line instead of an array of dots. So if you print a fine line of a very specific width – that would be a start.

    Also; we have calibrated the microscope to the “dot” on the “Foldscope.” Label on the tape used with making slides. The dot I believe was roughly 100 microns in width. Try using that to estimate what number your cells are.

    Cheers
    Manu

  2. rprabala says:

    @Prof. Prakash: Thanks for the suggestion! I’m updating the post above.

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