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I took the photograph below of some tree rings. Each division on the ruler is 1 millimeter:

enter image description here

Each tree ring (the areas between the pizza crusts) represents one seasons worth of growth. The growing season is from about March to October. My question is about the small lamellae or dark bands that make up each ring. I have placed a green box around one set of these bands. What are they?

These small bands all seem to be the same width, so tree rings that are wider (good years) have more of them, and rings that are narrow (drought years) have fewer.

What are these bands?

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Not as a confident answer but as a comment... to provide image.

The wood TS looks like ring-porous, Oak (Quercus sp.) wood (Not as identification but anatomical features are comparable).

The dark bands (radial here) seems to be xylem fibres, and bright bands (radial here), seems to be xylem parenchyma.

This is a magnified image of wood of post oak (Quercus stellata). oak. Source, URL http://www.wood-database.com/wp-content/uploads/post-oak-endgrain-zoom.jpg

where it seems to me

labelling seems to me

If there is anything wrong in my knowledge, inform me and feel free to downvote this answer. If any better answer comes, I'll delete this answer.

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  • $\begingroup$ My question is about the schlerenchyma. Why does it have a banded appearance? $\endgroup$ – Imprisoned Rhesus Sep 8 '16 at 19:25
  • $\begingroup$ I'm not sure in my labelled diagram about they are xylem fibre or something other, so I kept a place of doubt in my pictured-comment. However, though a certain repeating pattern helping here to all-sort of tissues distributed uniformly, maybe behind the exact radial-banding patterns there is no specific 'purpose'. All phenomena have 'cause', but some phenomena can have no 'purpose'. $\endgroup$ – Always Confused Sep 9 '16 at 5:55
  • $\begingroup$ or may be there is some purpose/advantage $\endgroup$ – Always Confused Sep 10 '16 at 2:16
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These are the annual rings that are usually found in areas /regions where environmental conditions are not uniform throughout the year. These are formed due to the activities of cambium (bundle of vascular tissue in plants showing secondary growth).

In spring it is lighter in color and has lower density whereas the autumn wood has high density and dark in color with higher density. Spring wood - High activity, produce large no. of cavities Autumn wood - Low activity, less lumens and cavities.

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    $\begingroup$ Read the question more carefully. $\endgroup$ – Imprisoned Rhesus Sep 8 '16 at 19:24

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