What does it mean for something to be intelligent? Does it need to be human, have a central nervous system, or exhibit the ability to learn and make cognitive decisions? Scientists have been exploring these questions and have discovered something incredible: studies show that trees should be considered intelligent, despite their current image as little more than nature's providers.
This comes from evidence that these organisms can communicate with each other through mycorrhizal fungal networks to help them adapt to their environment and combat stressors. Mycorrhizas, literally meaning "fungus roots," involve 95% of plant families in symbiotic relationships. Studies have found that plants and trees provide nutrients to the fungus as it in turn makes root growth less energetically costly and allows for communication within the
highly active plant root apex, or "root-brain." Tree and plant communication is a complicated topic, and there are endless processes and factors that aid it and benefits that come out of it.
A couple benefits include communicating defense signals to mitigate negative impacts environmental stressors and transferring nutrients between organisms. In their study, Song, Simard, Carroll, Mohn, & Zeng research the ability of Douglas-fir trees to communicate with another species, the ponderosa pine.
Their study focused on how the network of mycorrhizal fungus living in the roots of the Douglas-fir trees helped the trees overcome injury and communicate this stress to neighboring pines. They hypothesized that when under stress, the Douglas-firs would send signals to ponderosa pines to better prepare them for the same threats.
To study this, the researchers separated saplings of the two species into three groups: one group where roots were free to grow without barriers, and two groups with mesh bags around their roots. Of the two bagged groups, one had 0.5 μm sized holes, just small enough block fungal growth, and the other had 35 μm sized holes which still blockaded root growth but allowed the transfer of the fungus. To see how the trees would react to threats, budworms were put on each of the Douglas-fir samples. What they found is shown below:
Figure: germination rate (%) of the Douglas-fir and ponderosa pine samples in all three of the treatments (Song et al., 2015).
These results reveal to us an incredible concept. They prove that when the Douglas-fir samples have the capability to transfer signals to other trees, the survival of those trees is increased. Essentially, the root system that is developed by trees is just like the nervous system in our human bodies; chemical signals and hormones are communicated.
The idea that trees are intelligent enough to communicate threats to each other gives us a new perspective on trees as being even more complex than was previously understood. However, I think that there must be more to their communication than this, and it would be interesting to see just how extensive this inter-tree communication really is. How far does it reach? What other signals are exchanged in root-systems? At the very least, I hope that research like this can help us appreciate trees more and encourage empathy for the forests of our world.
References:
Song, Y., Simard, S., Carroll, A. et al. Defoliation of interior Douglas-fir elicits carbon transfer and stress signalling to ponderosa pine neighbors through ectomycorrhizal networks. Sci Rep 5, 8495 (2015). https://doi.org/10.1038/srep08495
This study is so cool! I had heard of these fungi before but I never knew how they worked. It is so interesting to me that they can communicate like nerves. The fact that it is stressors that allow them to communicate its so cool, because that suggests that these species evolved that way in order to better survive, which likely means human intelligence is caused by the same thing. The questions you provoke at the end make me want to learn more about this topic, adding to the quality of the article.
ReplyDeleteVery interesting study and very good post! I liked how catchy the first paragraph is and it hooked me to keep reading further. Good job with the take home message for us to appreciate plants more.
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