Source SHIGO TREE ANATOMY
The second increment maintains a symplast therefore is sapwood, yet the vessels are plugged thus known as non-conducting sapwood. This is common with species of white oak. The vessels here are plugged with tyloses. Trees plug vessels in at least 7 different ways. The current growth increment is the only conducting sapwood in this sample.
As you can see the 2nd increment 3rd and 4th are plugged with tyloses. You can see the purple in the sapwood where there is parenchyma cells storing starch. This sample was stained with I2KI.
In red oaks sapwood is all conducting. However, they do form traumatic tyloses which would be within color-altered wood from a wound or injury within the sapwood.
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John A. Keslick, Jr.