Dendrochronology cross dating

The secondary vascular tissues are aligned, forming radial files of cells that are produced from a single cambium initial cell that you can locate between the xylem and phloem.

The primary vascular tissues do not form neat radial files; the cells in the primary vascular areas appear to be much more "random" in pattern.

Through the winter very few cell divisions occur because of the cold.

First we will review the layers of the primary dicot stem from outside to inside.

On the exterior we have the epidermis which has developed from the protoderm. Beneath this is the cortex that may do photosynthesis in green stems but may also have respiration and storage functions in other species. These consist of four layers: toward the epidermis a "bundle cap" of fibers, functional primary phloem, vascular cambium (aka cambium), and primary xylem toward the interior. All of these tissues arose by cell division that occurred at the stem apex, and matured into the differentiated cell types and tissue layers from there.

Additional layers lead up to the year the tree died (gypsy moth infestation finished it off in the early 1980s).

An additional slide shows some specimens of Bristlecone pine (Pinus aristata).

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