In an experiment, using the elodea stalk, you are able to expose more underlying tissue and the process can be executed more quickly and it's easy to replicate the natural position for a more realistic result.
hope this helps
The tissues found within the vein if I must say are xylem and phloem. Glad I can help.
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There are so many examples for that in different areas, like biology experiment carried out in our lab recently.
Here's one link: https://www.creative-biogene.com/Robust-Tn5-Transposase-EMQZ1422-1271506-26.html