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 21 wood DHJanzen100260.jpg high resolution
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We all know about woody. But have you ever asked yourself why wood is woody? For support, of course. Yes, but can you imagine what would have happened to that support - made of sugar after all - if each passing animal, fungus and bacteria could take a bite out of it? Would is a complex structure of cellulose (a sugar) with various kinds of lignins (alcohol polymers) attached that is essentially indigestible to all but bacteria and protists - they are the only organisms that make the enzymes needed to break it down. Visualize the first emergent, growing, upright plants. They were standing lunch for whoever was around - a large pile of organic goodies. There must have been very intense selection right then for a structural compound that was indigestible - and it has been with us ever since. Not even the plant can digest its own structural sugars. Incidentally, another sugar that is very difficult to digest is starch, an energy storage compound for plants. I wonder why it is largely indigestible? |
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