What makes trees grow?

Back in the 17th century, when the modern scientific method was still being worked out, a Flemish scientist / philosopher / alchemist named Jan van Helmont set out an experiment to determine what was the principle agent in tree growth - water or soil?

Up to that point, nobody had really bothered to try and figure out what caused a tree to grow (or any plant for that matter). People might discuss it. They might have there pet ideas, but none of those ideas were put to the test - they were just common sense, or good arguer might make a compelling case, or it was clearly documented in some ancient text (people have this really annoying habit of assigning far greater authority to something that has been written down, or ascribed to some dead person than to their own thoughts and ideas).

Anyway, nobody really knew what was the principle agent in a tree growing - water or the soil.

So Jan performed an experiment. He got himself 200lbs of soil and put it in a box. He planted a 5lb tree in the soil and covered the soil so that nothing would be admitted, save for the water he watered it with.

For 5 years he watered that tree and it grew and grew and grew. At the end, he removed the tree, carefully disentangled earth and roots and weighed both the tree and the soil. The tree weighed 169lbs; the soil had lost only 2 ounces of mass.

So were did the tree gain its additional mass if not from the soil? Clearly it was the water with which Jan has watered his tree.

This was actually a very good experiment. It carefully controlled two variables: soil and water. It came to a solid and sound conclusion, but it was wrong. It was wrong, not because of any problem with the experiment, but because of a lack of wider general knowledge. It would have been incredibly insightful of Jan to go beyond his obvious conclusion, notwithstanding it was he who brought the word gas to us (by way of the Greek kaos) and he also discovered carbon dioxide. Nevertheless, he believed that everything arose from the waters mentioned in Genesis. This was what his experiment was about - proving that water that is the elemental constituent of everything.

Four hundred years later, we understand thing s a lot better and realize that photosynthesis is responsible for the growth of the tree.

While present knowledge is better and more complete than in the past, I am always skeptical whenever I hear scientists' carefully laid out experiments and obvious conclusions because I always wonder if they missed something. Maybe they asked the wrong question or got an answer that is meaningless because that answer needs to be trimmed down further. What if the obvious answer is not really so obvious - like Jan van Helmont and his water.

Image copyright of me.


ghee said…
nice pic richard,i like the colour of fall:)

what if the obvious answer is not so obvious?

thats what i got from your entry,and i took it with deeper meaning. :)
I don't get why he didn't have 2 trees the same size and put one in soil and the other in no soil and give both water? And 2 more trees both in soil and water one and not the other?

You're right about giving more credibility when something is written...especially when typed..it looks so business-like and real. It looks like something official to be taken seriously and to be believed.
Matt said…
I could definitely see you as one of the MythBusters. You have a talent for these things.

Nice picture. Some red leaves, yes, but you need more. Maybe I can send some to you. :)
Richard said…
ghee: I reused the picture because I was too lazy to look for a new one. It was taken 13 or 14 years ago (I think, maybe as recently as 12). It was in a place called Gatineau Park.
That is precisely what I was getting at: “The obvious answer may not be the obvious answer.”

MOI: You have to remember that at his time, the idea of experiment and observation was a relatively new thing. Up to that time, the preferred method of knowledge acquisition was through dialectics (much in the manner of the Sophists). Of course, there are many avenues of modern day science, particularly physics, where "thought experiments" (another expression for dialectics - as far as I am concerned) are common. The difference is that the thought experiments are then tried out in the lab.

matt All the leaves are down now. We had plenty of red leaves. I like this picture because it has colours you normally don't see - like pink.
KayMac said…
interesting...i really enjoyed this post and the comments.
Anonymous said…
kaymac: you are welcome
busybee said…
Good question asked. The same question can also be applied to human relationship or human development.

I see it as many, many, many factors.... nature vs nurture debate again.

In the biclical sense, 1 Corinthians 3:7 says,
"So neither he who plants nor he who waters is anything, but only God, who makes things grow." :)
Richard said…
bee: I agree from the biblical point of view. My point (if I ever have a point in my posts) was simply that we sometimes when we think we have the answer to something, we might be wrong or incomplete in our knowledge and conclusion.

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