I got this picture from the Wikipedia entry for Tracheid. What are the roundish objects in the sketch?

Also are tracheids sclerenchyma cells?

Sketch of tracheid

  • 2
    $\begingroup$ It's a good idea to do some reading before posting. Your question whether tracheids are cells is answered in the very first sentence of the article that you took the diagram from: "Tracheids are elongated cells…" $\endgroup$
    – David
    Dec 21 '18 at 15:06

The 'roundish stuffs' you are seeing are called 'pits'. The Dictionary of Botany defines a pit as '[a] cavity in the secondary cell wall, allowing exchange of substances between adjacent cells'. The pit itself is composed from a aperture, named the pit cavity and an environing membrane called the 'pit membrane'. The pit is comparatively analogous to the plasmodesmata connecting protoplasts by thin connecting vessels. The difference exists in the presence of pits within the xylem while plasmodesmata arise between other non-vascular cells additionally.

To respond to your second question, where sclerenchyma cells are strengthened, lignified cells, tracheid cells are indeed the 'tracheary' or vascular specialisation of sclerenchyma tissue.

For information regarding the Dictionary of Botany, the website is available from: http://botanydictionary.org/pit.html

Information concerning ground tissue is available from: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/ground-tissue


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