What would the appearance and structure of trees be like if they used chitin, instead of lignin, for cell walls? This is assuming that all other properties are basically unchanged.

These trees would be in a tropical environment with nutrient rich soil and plenty of water and sunlight available. They utilize photosynthesis and have efficient vascular systems.

Would chitin effect how hard or soft they can get? Or how tall they can grow?

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    $\begingroup$ A basic fundamental aspect of natural evolution is that it won't follow the same path if restarted. As the great Stephen Jay Gould said, if we could rewind the tape of life and play it again we would see a different development unfold. Since this question asks what if plants were more related to fungi, this means that a change would have been introduced a very long time ago; the end results are completely and totally unpredictable. Not even basic elements, such as the alternance of generations, would be necessarily the same. The question is not simply too broad, it's unbounded speculation. $\endgroup$
    – AlexP
    Apr 5, 2019 at 18:14
  • $\begingroup$ Hi, welcome to Worldbuilding,SE! If you havent already, please take the time to read through our Tour page. This seems like a good question but its a little bit on the short side. Can you tell us what kinds of plants you have in mind (for example, there is a large difference between the structure of grass and a tree) and what the general environment is like? (i would assume you are refering to a temperate environment?) $\endgroup$ Apr 5, 2019 at 18:15
  • $\begingroup$ BTW, to help with re-framing the question: can you explain in a few short paragraphs what is current "appearance and structure of plants"? Remember than plants include mosses and oak trees, ferns and grasses. Remember that "grasses" include the bamboo and banana, besides the usual wheat and dandelions. $\endgroup$
    – AlexP
    Apr 5, 2019 at 18:18
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    $\begingroup$ Plants use lignin instead of chitin. Cellulose is instead of meat. Your substitution is incorrect. $\endgroup$
    – Gangnus
    Apr 5, 2019 at 20:43
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    $\begingroup$ I have taken the liberty to edit your question based on the comments and an answer posted to this question. I have changed all mentions of cellulose to lignin as, based on the comments, seems to be what you meant. If my edit is accepted, feel free to change it back if it does not match what you meant. $\endgroup$ Apr 5, 2019 at 21:42

2 Answers 2



large tentacle-like structures protrude out of thr ground Credit to Philip Newsom

Whilst not plants as you specify in your answer, you may very well be able to draw inspiration from this. From an answer i received on my own question i learned that prototaxites were large fungal structures that existed long before trees dominated the earth. These structures could grow up to seven meters tall.

A series of irregular rings that expand outwards, similar to that of tree rings https://www.researchgate.net/figure/Transversely-sectioned-Prototaxites-fossil-This-overview-image-originating-from-a_fig1_51174561

As you can see, these structures had rings similar to that of trees. However, unlike trees, they were composed of chitin. The image you see here has been edited to enhance the ability to distinguish the outlines of each ring. The pressence of rings shows that these prototaxites were able to withstand changing environments and endure for a long time, no small feat for a structure of that size.

Willk compares this to the modern bracket fungus which produces spores and is hard as wood, it is also called the shelf fungus as it is used to make actual shelving.

Applying this to your question, your trees would likely have a very similar internal structure to these prototaxites, still consisting of rings but their shape and colour may be different than those you find in wood.

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    $\begingroup$ Yes, this is definately something I will look into for inspiration. Thank you. $\endgroup$ Apr 5, 2019 at 19:40

Note: This answers refers to the original version of the question, which was about replacing cellulose with chitin.

The structural material in tree mechanics is not cellulose, but lignin.

Lignin is a class of complex organic polymers that form key structural materials in the support tissues of vascular plants and some algae. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily. Chemically, lignins are cross-linked phenolic polymers.

Chemical structure of chitin    Chemical structure of cellulose

The chemical structures of chitin (left) and cellulose (right). See how similar they are. Pictures from Wikipedia.

Chemically, cellulose and chitin are very similar; they are both simple polymers, derived from glucose. Lignin (from Latin lignum, "wood") is entirely different:

Chemical structure of lignin

A possible chemical structure of lignin. Note the aromatic rings, utterly absent from chitin and cellulose, and the numerous and irregular cross-links between units. Picture by Karol Głąb, available on Wikimedia under multiple licenses including a public domain dedication.

As a biopolymer, lignin is unusual because of its heterogeneity and lack of a defined primary structure. Its most commonly noted function is the support through strengthening of wood (mainly composed of xylem cells and lignified sclerenchyma fibres) in vascular plants. (Wikipedia, s.v. Lignin)

The conclusion is that replacing cellulose with chitin is immaterial; the strength of the mechanical structure is given by another material entirely.

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    $\begingroup$ Oh yes, massive. Lignin is what makes wood a valuable material for its strength and resistance against environmental factors. Cellulose and chitin are much less strong, and rot very much faster. Plants have used lignin to get up and stay up for a very long time. $\endgroup$
    – AlexP
    Apr 5, 2019 at 19:52
  • $\begingroup$ Sorry, I deleted my original comment in order to dig a little deeper into the information you provided. This helps quite a bit. $\endgroup$ Apr 5, 2019 at 20:00
  • $\begingroup$ You are correct, +1 from me, I had already made a comment of my own about it, too. But that means that the question is incorrect and without correction should be closed... $\endgroup$
    – Gangnus
    Apr 5, 2019 at 20:44
  • $\begingroup$ @Gangnus I have corrected the information $\endgroup$ Apr 5, 2019 at 21:46

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