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We Slowed Down

Classifying x-rays stopped being fun very quickly today. Emma and I had divided the slides randomly and were each doing half, and I finished mine first so I decided to classify a handful of hers and see how the numbers matched up. They didn’t. Around 50% of the slides I recounted had new numbers. All of the discrepancies were because achenes were in between being full and partial or partial and empty (partial achenes were fertilized, but the embryo either did not develop normally or was destroyed). Together we went back to go over the discrepancies, and we came up with a few rules to make things clearer in the future. We were already working with a few rules that Danny had set out for defining partials:

  1. The embryo is fragmented
  2. The embryo has concave (curved inward) or irregular edges
  3. The width of the embryo is less than half the width of the achene at its widest pointThis was a good start, but we still found plenty of ambiguous achenes. Our new definitions for “partial” are:
  4. Both the top and bottom of the embryo is rounded, and there is plenty of space not filled within the achene. Looking for space along the sides of the achene can help identify this one.

    xray-rounded-ends

    (71top)

  5. A strong, bright line inside an achene indicates a partial achene, whether it curves or not. Make sure this is distinct from the edges of the achene.

    (59bot)

    (59bot)

  6. If the achene is bright, but not as bright as regular full achenes, the achene is partial (this can be described as cloudiness).

 

We also came up with a few hints (learned the hard way):

  • Be careful of florets–they can show up as brightly as embryos, but don’t count them! The florets at top left of this image are almost as bright as the embryos bottom-right, and could be mistaken for partial achenes.

    the florets at top left are almost as bright as the embryos bottom-right, and could be mistaken for partial achenes. (93top)

    (93top)

  • If a bright spot has no outline of an achene around it and no band near it, and it isn’t a recognizable shape, assume it is chaff and let it alone.
    • The “band” is the little bright line at the top of x-rayed achenes.
  • When there is less contrast in an image and the brightness of embryos is hard to see, look at the bands at the tops of each achene. These are usually about as bright as embryos, so you can set a standard by that shade.
  • xray-contrast (70bot)

It is also worth noting that we decided to count achenes as full when the embryos don’t fill the entire outline: a space between the embryo and the achene is definitely permissible, and even smaller embryos count when they still maintain the proper shape (flat/convex top, pointed bottom) and aren’t smaller than half the width of the achene.

 

It was a long day of checking and rechecking classifications, but we’re finally happy with our counts. Now we’re working on a poster to help recruits learn the difference between informative and uninformative achenes, and Amy is helping us compile data. We’re officially out of the collection phase!

Always tired,

Mikaela

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