Week 31
When I walk round my renatured land there is plenty I do not understand, other than it is clear Nature is running me, not the other way around. Yet I find it strange that plants seem so territorial. Yes, there are specific soils, pHs and conditions that certain plants seek out, and when I see a clump of something colourful, I credit it to my renaturing brilliance. Without me, I declare, that clump would not be there.
How wrong I am, as I am not brilliant at all. I am staggering through as best I can, learning day by day, and realising that plants have metaphorical minds of their own. If a flower decides to appear it will do so. If it elects to take a year out, it will do that as well. Flowers side with friends and do their best to repel enemies. Meanwhile young trees like to stay near their mothers and prefer to grow in groups rather than alone. I look at my oak[i] and yew[ii] seedlings, that are right beside Mum. As for my silver birch[iii], there are so many seedlings I almost feel under attack. They are grouped together on my land, near the top of a hill, and appear to like each other’s company.
If I look at the base of any ageing tree, the area is scattered with saplings, each welcoming the care offered by the older tree while waiting for it to fade and die. It is then that a sapling will take over. A clump of St John’s Wort[iv] shows off its glorious yellow display and will grow right up to its purple neighbour, in my case lavender[v], but will go no further. Both are driving pollinator insects crazy. I sense the two plants are communicating by some mechanism underground.
“This is my territory,” says the yellow.
“This is mine,” says the purple.
Somehow the two survive, tolerating each other’s company, yet I have no real idea how. Plants seem to discriminate and do their best to remain with their own kind. This behaviour seems...well...almost human, although I doubt modern society would encourage me to say so.
The concept of plants discriminating between different types of plant is rooted in their responses to different environmental signals, not in conscious decision-making, as one might understand in animals or humans, although that is now being questioned. The boffins have undertaken plenty of research in this area and have reached several conclusions. These are:
1. Kin Recognition[vi]: Some plants can recognise their kin, i.e., closely related individuals, and modify their growth strategies accordingly. For example, a study in 2007[vii] used the American sea rocket (Cakile edentula)[viii] to demonstrate this concept. When grown in the same pot, siblings did not compete as fiercely for root space as non-siblings did. The interpretation was that there is an evolutionary advantage for plants to avoid competing with their relatives, as it improves the overall fitness of their genetic lineage. Kin recognition is seen in many plants[ix],[x], mainly below ground although sometimes above ground, and can occasionally be absent completely[xi].
2. Neighbour Detection and Response: Many plants can detect and respond to neighbouring plants, whether they are of the same species or not. This can be seen in the shade avoidance syndrome[xii] - plants get syndromes, just like you and me. With shade avoidance, plants grow taller and allocate less to root growth when they perceive the presence of neighbouring plants. They use cues for this, such as light quality and quantity, mechanical stimulation, and plant-emitted volatile chemicals.
3. Mycorrhizal Networks: Some plants can influence which other plants succeed or fail in their local environment through mycorrhizal networks, which are symbiotic relationships between fungi and plant roots. The plants feed the fungi with photosynthetic products while the fungi feed the plants with mineral nutrients foraged from the soil[xiii]. In recent years there has been much said and written about the mycorrhizal networks of trees[xiv],[xv], but it is not just trees that use this, smaller plants do as well. Some 90% of plant species around the world[xvi] employ this system.
4. Allelopathy[xvii]: Some plants can release substances (allelochemicals) into the environment that inhibit the growth and development of neighbouring plants. Some of these are the so-called Volatile Organic Compounds (VOC)[xviii], which are crucial in plant defence against herbivores and pathogens[xix]. This phenomenon, known as allelopathy, is a form of chemical warfare and can give the releasing plant a competitive advantage. A well-known example is the Black Walnut tree (Juglans nigra)[xx], which releases juglone[xxi], a compound that is toxic to many other plants. Bioactive compounds are of particular interest as they offer an alternative to manmade chemicals in the garden, especially with lawsuits underway for certain other manmade materials[xxii],[xxiii],[xxiv].
It was once thought that although plants could behave in these different ways, it was not the result of conscious behaviour. Yet is that view still held? I am unsure it is. Take the Mimosa pudica[xxv] , the so-called touch-me-not or shameplant[xxvi], that folds its leaves when touched. The plant can be anaesthetised, just like a human, with ether or local anaesthetic, and the leaf-folding stops. These effects are not solely confined to Mimosa pudica, and it is probable that all plants can be anaesthetised[xxvii]. It certainly applies to the Venus flytrap[xxviii].
Some also say that plants can talk, using ultrasonic sounds to highlight stress[xxix]. They are said to communicate not only with each other, but with animals and people, too. There was a time, the mid-19thcentury, when Charles Darwin and his son Francis suggested that plants had a brain-like structure at the tips of their roots[xxx][xxxi]. That has now been disproved but the Darwins certainly spotted that plants are cleverer than we think. It is known that speaking nicely to a plant can support its growth[xxxii], whereas yelling at it will not[xxxiii]. Some have claimed that plants can even recognise people[xxxiv].
As I walk my land, and it does not cover a huge area, I find myself pondering extensively, as plants are sounding more like humans each day. There is manifestly more to a plant than I once thought and there is clearly much research to be done. I sense we are at the tip of what will one day be seen as a huge iceberg. Vegans and vegetarians beware. By relinquishing meat, you may be doing plenty for yourself, for others, and certainly for the environment[xxxv], but there are clear negative effects as well[xxxvi],[xxxvii]. It is not all about giving up meat, even if livestock accounts for nearly 80% of the world’s agricultural land but produces less than 20% of the world’s calories[xxxviii].
When it comes to plant communication, not only plant-to-plant but also plant-to-human, hugging trees comes to the fore. This is certainly something I have attempted, largely when I know other people are not looking, as they consider me crazy already. My prime target, and seemingly the most receptive, is a large Noble Fir[xxxix]near the top of my land. On occasion I have hugged it while furtively looking this way and that. Paradoxically, tree hugging does make me feel more content. The process is known to increase the levels of the hormone oxytocin, which is responsible for emotional bonding and feelings of wellbeing, calmness, and trust. Touch is an excellent way of increasing oxytocin production[xl], which may be how tree hugging works. I am not the only odd one, as there are even tree hugging world championships, in Finland[xli].
So, when I walk my land and see clumps of flowers grouped tightly together, discrimination is at play, in a way that human society would not permit. It is the way of things with Nature. My harebells show this well, as they are out in full glory at the moment. One day there are none, the next there are plenty. The harebell[xlii] is meant to seek dry ground, which is not as one might expect in Lakeland, but there was a dry month a few weeks ago, so that may have something to do with the glorious, sprawling blue of my harebells. The plant is edible, makes a fantastic addition to a salad and is native to the UK[xliii]. It has also been used as a blue dye for Scottish tartan[xliv], perhaps why it is also called the Scottish bluebell. But my harebells are extremely territorial. Clumped together, they sit immediately beside a patch of yarrow[xlv], the occasional lonely harebell interloper eking out an existence surrounded by yarrow, but the converse does not apply. Underground somewhere my harebells are sending a message, “Yarrow, stay away.”
Each species has its own method of doing things but there is a commonality that binds us all. It is why I like renaturing as it is a reminder that mankind forms part of Nature and is not dominant over it. Just look at the wildfires taking place worldwide as I write these words. If there was ever a lesson needed in what mankind’s climate inertia is doing, look at wildfires. They are increasing speedily while 80% are caused by...wait for it...people[xlvi]. That is not a good sign.
***
Acknowledgement
Take it from me - none of this would be possible without the help of RSG Horticulture. Rufus, who runs it, has far more energy than me and is full of ideas and skills. Do contact him through https://www.rsghorticulture.com.
A thought...
I have been asked to spread the word about glyphosate, which I am happy to do. Here's a link and logo for you:
References
[i] See week 23 entry.
[ii] See week 2 entry.
[iii] See week 6 entry.
[iv] See week 27 entry.
[v] Royal Horticultural Society. Lavender (Lavandula spp.). Lavender is a popular, aromatic, drought-tolerant garden plant. There are many different species and subspecies, and they are easy to grow and associate well with other shrubs, perennial plants, and roses. Long-lived and hardy border plants include cultivars of the English lavender (Lavandula angustifolia and L. × intermedia). Other lavenders, including French lavender (Lavandula stoechas), are slightly less hardy and can be short-lived so need replacing every few years. All lavenders are popular with bees, butterflies, and other pollinators. See https://www.rhs.org.uk/plants/lavender. Accessed 30 July 2023.
[vi] Anten NPR, Chen BJW. Detect thy family: Mechanisms, ecology and agricultural aspects of kin recognition in plants. Plant Cell Environ. 2021 Apr;44(4):1059-1071. doi: 10.1111/pce.14011. Epub 2021 Feb 18.
[vii] Dudley SA, File AL. Kin recognition in an annual plant. Biol Lett. 2007 Aug 22;3(4):435-8. doi: 10.1098/rsbl.2007.0232. PMID: 17567552.
[viii] Cakile edentula. See https://en.wikipedia.org/wiki/Cakile_edentula. Accessed 27 July 2023.
[ix] Marler TE. (2013). Kin recognition alters root and whole plant growth of split-root Cycas edentata seedlings. HortScience, 48, 1266–1269. https://doi.org/10.21273/hortsci.48.10.1266
[x] Semchenko M, Saar S, Lepik A. (2014). Plant root exudates mediate neighbour recognition and trigger complex behavioural changes. New
Phytologist, 204, 631–637. https://doi.org/10.1111/nph.12930
[xi] Lepik A, Abakumova M, Zobel K, Semchenko M. (2012). Kin recognition is density-dependent and uncommon among temperate grassland plants. Functional Ecology, 26, 1214–1220. https://doi.org/10.1111/j. 1365-2435.2012.02037.x
[xii] Pierik R, de Wit M. Shade avoidance: phytochrome signalling and other aboveground neighbour detection cues. J Exp Bot. 2014 Jun;65(11):2815-24. doi: 10.1093/jxb/ert389. Epub 2013 Dec 9.
[xiii] Walder F, Niemann H, Natarajan M, Lehmann MF, Boller T, Wiemken A. Mycorrhizal networks: common goods of plants shared under unequal terms of trade. Plant Physiol. 2012 Jun;159(2):789-97. doi: 10.1104/pp.112.195727. Epub 2012 Apr 19.
[xiv] Grant R. Do Trees Talk to Each Other? March 2018. See https://www.smithsonianmag.com/science-nature/the-whispering-trees-180968084/#:~:text=Scientists%20call%20these%20mycorrhizal%20networks,or%20perhaps%20an%20economic%20exchange. Accessed 27 July 2023.
[xv] Wohlleben P. The Hidden Life of Trees. Greystone Books 2018. 978-1771643481. See https://www.amazon.co.uk/Hidden-Life-Trees-Illustrated/dp/177164348X/ref=sr_1_2?crid=2ARH0TM7FE0MI&keywords=the+hidden+life+of+trees+peter+wohlleben&qid=1690515668&sprefix=the+hiodden+life+of+trees%2Caps%2C114&sr=8-2. Accessed 28 July 2023.
[xvi] Yih D. Food, Poison, and Espionage: Mycorrhizal Networks in Action. 15 November 2017. See https://arboretum.harvard.edu/stories/food-poison-and-espionage-mycorrhizal-networks-in-action/. Accessed 28 July 2023.
[xvii] Allelopathy. See https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/allelopathy#:~:text=Allelopathy%20is%20the%20direct%20or,1937%3B%20Rice%2C%201984). 2017. Accessed 28 July 2023.
[xviii] Vivaldo G, Masi E, Taiti C, et al. The network of plants volatile organic compounds. Sci Rep 7, 11050 (2017). https://doi.org/10.1038/s41598-017-10975-x. According to their biosynthetic origin and chemical structure, plant volatiles can be grouped into isoprenoids or terpenoids, but also oxygenated VOCs (OVOCs), such as methanol (CH4O), acetone (C3H6O), acetaldehyde (C2H4O), methyl-ethyl-ketone (MEK, C4H8O) and methyl-vinyl-ketone (MVK, C4H6O); in few cases, sulfur compounds (e.g. in Brassicales) and furanocoumarins and their derivatives (e.g. in Apiales, Asterales, Fabales, Rosales) are also found.
[xix] Heil M, Bueno JCS. Within-plant signaling by volatiles leads to induction and priming of an indirect plant defense in nature. Proc. Natl. Acad. Sci. USA. 2007;104:5467–5472.
[xx] Juglans nigra. See https://en.wikipedia.org/wiki/Juglans_nigra. Accessed 27 July 2023.
[xxi] Romano R, Aiello A, Meca G, et al. Recovery of bioactive compounds from walnut (Juglans regia L.) green husk by supercritical carbon dioxide extraction. International Journal of Food Science and Technology 2021, 56, 4658–4668
[xxii] ConsumerNotice.org. Roundup. See https://www.consumernotice.org/environmental/pesticides/roundup/. Accessed 28 July 2023.
[xxiii] ConsumerNotice.org. Roundup Alternatives. See https://www.consumernotice.org/legal/roundup-lawsuits/. Accessed 28 July 2023.
[xxiv] ConsumerNotice.org. Roundup Lawsuits. See https://www.consumernotice.org/legal/roundup-lawsuits/
[xxv] Lawrence N. The radical new experiments that hint at plant consciousness. See https://www.newscientist.com/article/mg25534012-800-the-radical-new-experiments-that-hint-at-plant-consciousness/#:~:text=He%20believes%20that%20the%20flexible,as%20a%20sort%20of%20consciousness. Accessed 27 July 2023.
[xxvi] Mimosa pudica. See https://en.wikipedia.org/wiki/Mimosa_pudica. Accessed 28 July 2023.
[xxvii] Frazer J. Plants, Like People, Succumb to Anesthesia. See https://blogs.scientificamerican.com/artful-amoeba/plants-like-people-succumb-to-anesthesia-video/. Accessed 27 July 2023.
[xxviii] Venus flytrap. Dionaea muscipula. See https://en.wikipedia.org/wiki/Venus_flytrap. Accessed 27 July 2023.
[xxix] Yang A. Plants can talk. Yes, really. Here’s how. 12 April 2023. See https://www.nationalgeographic.com/science/article/plants-can-talk-yes-really-heres-how#. Accessed 27 July 2023.
[xxx] Hanano A, Murphy C, Murphy DJ. Plants can “speak” to each other. 15 April 2022. See https://kids.frontiersin.org/articles/10.3389/frym.2022.658692. Accessed 27 July 2023.
[xxxi] Baluska F, Mancuso S, Volkmann D, Barlow PW. The 'root-brain' hypothesis of Charles and Francis Darwin: Revival after more than 125 years. Plant Signal Behav. 2009 Dec;4(12):1121-7. doi: 10.4161/psb.4.12.10574.
[xxxii] Dodd S. 'They respond to vibrations': does talking to plants actually help them grow?See https://www.theguardian.com/lifeandstyle/2021/jan/11/they-respond-to-vibrations-does-talking-to-plants-actually-help-them-grow#:~:text=“But%20some%20research%20shows%20that,115%2D250hz%20being%20ideal.” Accessed 27 July 2023.
[xxxiii] Khait I, Obolski U, Yovel Y, Hadany L. Sound perception in plants. Semin Cell Dev Biol. 2019 Aug; 92: 134-138. doi: 10.1016/j.semcdb.2019.03.006. Epub 2019 Apr 27. PMID: 30965110.
[xxxiv] Funk A. A String of Unusual Experiments Claim to Show Plants Can Think. Few Scientists Are Buying It. 28 August 2019. See https://www.discovermagazine.com/planet-earth/a-string-of-unusual-experiments-claim-to-show-plants-can-think-few#. Accessed 27 July 2023.
[xxxv] Environmental Benefits of a Vegetarian Diet. See https://www.topsdaynurseries.co.uk/environmental-benefits-of-a-vegetarian-diet/#:~:text=Reduce%20Carbon%20and%20Greenhouse%20Gas%20Emissions&text=This%20means%2C%20by%20replacing%20meat,and%20other%20greenhouse%20gas%20emissions. Accessed 28 July 2023.
[xxxvi] Simon. Negative Effects Of Veganism On The Environment. 14 May 2023. See https://sustainability-success.com/negative-effects-of-veganism-on-the-environment/?utm_content=cmp-true. Accessed 27 July 2023.
[xxxvii] Gray R. Why the vegan diet is not always green. See https://www.bbc.com/future/article/20200211-why-the-vegan-diet-is-not-always-green. Accessed 27 July 2023.
[xxxviii] Ritchie H. How much of the world’s land would we need in order to feed the global population with the average diet of a given country? 3 October 2017. See https://ourworldindata.org/agricultural-land-by-global-diets. Accessed 28 July 2023.
[xxxix] See week 6 entry.
[xl] The benefits of hugging trees. 25 May 2022. See https://silvotherapy.co.uk/articles/benefits-of-hugging-trees. Accessed 27 July 2023.
[xli] Tree Hugging World Championships. See https://www.halipuu.com/treehuggingworldchampionships/. Accessed 27 July 2023.
[xlii] Harebell. Campanula rotundifolia. In Scotland, the harebell is sometimes known as the 'bluebell'; elsewhere, it has picked up various local names, including 'witches' thimbles' and 'fairy bells', alluding to magical associations. See https://www.wildlifetrusts.org/wildlife-explorer/wildflowers/harebell. Accessed 27 July 2023.
[xliii] Harebell. https://www.naturescape.co.uk/product/harebell/#:~:text=Harebells%20are%20native%20to%20dry,into%20a%20bell%2Dshaped%20flower. See 27 July 2023.
[xliv] Harebells. See https://www.wildfooduk.com/edible-wild-plants/harebells/. Accessed 27 July 2023.
[xlv] See week 30 entry.
[xlvi] Center for Climate and Energy Solutions. Wildfires and climate change. See https://www.c2es.org/content/wildfires-and-climate-change/. Accessed 28 July 2023.
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