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Young birch with black and white birch bark in spring in birch grove against the background of other birches
Birch trees Adobe Stock licensed

Researchers: Trees “sense” their height and weight

We have only recently discovered how complex plant communications are

Trees rarely just fall over but we seldom stop to think about why they don’t.

Recently, University of Helsinki researchers discovered that trees can “sense” their weight in relation to their height and adjust their growth for stability. Manipulating the weight of downy birch trees, the team discovered that a tree can adjust its stem thickening in relation to its height, especially if the stem is free to move a bit. They were able to test this thesis by studying a mutant tree that sadly lacks that ability:

The researchers took advantage of a naturally occurring birch mutant named elimäki. This exceptional tree grows upright for three months, after which its stem suddenly bends at the very base, and the whole tree collapses.

The researchers showed that, unlike normal trees, elimäki trees fail to properly adjust their width to their increasing weight, which makes them less stable mechanically. The lack of a proper response in elimäki trees is linked to a single position (locus) in the birch genome, enabling the future identification of the mutated gene.

University of Helsinki, “Trees might be ‘aware’ of their size” at ScienceDaily, January 30, 2020

Birch trees offer plant biologists an advantage because they can be got to flower at six months. A typical hindrance to studies of intricate communications systems within and among trees is their slow growth and great longevity, compared to, say, the classic study plant Arabidopsis. The paper is open access.

We have only recently discovered how complex plant communications are. So some people have gone from thinking of them as green manure to supposing that they “think” or are conscious. Plant scientists recently found it necessary to protest that plants are not conscious.

We may sometimes confuse sentience (awareness of and response to the environment) with consciousness (a sense of self). Many mammals and birds have varying degrees of consciousness; it has not been established that any plants do.

Update: Reader David Spoede writes to say: “A forester once told and then showed me that a large tree growing at about a 20° angle had developed an oval trunk, rather than the standard round trunk, in order to cope with its unique stress. He said that the tree could very well still be there a hundred years from now despite its severe angle.”

Note: The illustration above of the downy birch, Betula pubescens, is by Radomil under a Gnu free documentation license.


Many discoveries have been made in recent years about the complexity of plant communications:

Can plants be as smart as animals? Seeking to thrive and grow, plants communicate extensively, without a mind or a brainSeeking to thrive and grow, plants communicate extensively, without a mind or a brain

Is salad murder? If we think plants are “equal organisms” with respect to humans, it’s not clear whether salad is or isn’t murder. Or whether murder is even a serious ethical problem.

and

Researchers: Yes, plants have nervous systems too. Not only that but, like mammals, they use glutamate to speed transmission


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Researchers: Trees “sense” their height and weight