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Ever since the best-selling book The Secret Life of Plants (1) was released in the seventies, well-intentioned folks have been showering their plants with love and attention, including talking to and playing Mozart for their plants to enhance their health and vitality. However, most of the science cited in that book was either flawed or never replicated.
What followed after this book’s debut was a staunch scientific bias negating any suggestion that plants could think, learn, feel, hear, smell, touch, see, taste or communicate in any way. Finally, after over forty years of scientific rigidity, new science is emerging that is re-opening this door into the secret life of plants.
Flowers Have Feelings Too
Monica Gagliano from the University of Western Australia has done studies showing that plants can actually learn, change their behavior and remember. (2) She rigged up a device that would allow 56 extra-sensitive ferns to fall 10 centimeters and come to an abrupt stop every 5 seconds for 60 drops. (Normally, these ferns instantly fold up when jarred in any way.)
In her study, many of the ferns reopened their leaves after just four to five drops, suggesting that they adapted to the drops and did not perceive them as a threat anymore. By the end of the 60 drops, all the ferns kept their leaves open as though they had gotten used to this stimulus and changed their behavior so as to not fold up upon being dropped. (2)
To rule out the possibility that the ferns were fatigued, after Gagliano performed the 60-drop test, she shook the ferns and they all immediately closed up. Interestingly, upon continuing the drops once more, the ferns again did not respond. They seemed to adapt very quickly to the fact that the drops were not a serious threat, pointing to the conclusion that these organisms are knowledge-accumulating systems. (2, 13)
To prove that the ferns had remembered the dropping stimulus, she put them back in the drop-experiment a week later, and then again a month later, and they all still ignored the drops. Gagliano was quick to remind her skeptical colleagues that in a similar experiment with bees, the bees forgot what they had learned in just 48 hours.
The Amazing Responsivity of Plants
In response to an herbivore chomping on the leaves of a plant or a neighboring plant, the plant will often prime itself for chemical warfare as a defensive maneuver. Plants often produce chemicals such as ethylene or tannins that many herbivores do not eat. Certain plants can even secrete toxic and poisonous chemicals that can make the herbivore sick or even kill it. (3)
In another study, when one sage brush leaf was clipped, both the clipped and the non-clipped sage brush neighbors experienced less insect damage for an entire season. This experiment suggests that the clipped or damaged sage brush plant put out a signal that it was under attack. This signal potentially alerted all of the sage brush plants in the area, triggering them to emit defense chemicals to protect from further attack. These defense chemicals warded off insects for an entire growing season. (4)
When they captured the emissions from the clipped sage brush, they measured over a hundred defense chemicals caught in a plastic baggie. (4)
Other studies have shown that when attacked, plants can “cry for help” by producing volatiles and chemical signals attracting carnivorous predators of the attacking herbivores. Specifically, research has shown that bean plants that were exposed to components of other bean plants damaged by spider mites or aphids were more attractive to carnivorous enemies of the spider mites or aphids, resulting in a potentially self-preserving tactic on the part of the plant. (5, 6) Interestingly, research also shows that parasitic plants have the ability to recognize prey at a distance and evaluate their nutritional value before deciding to invade them. (5, 7, 8) What’s more, it has been scientifically shown that sound waves elicit changes on plant’s molecular and physiological levels, affecting the plant’s gene expression. (5, 9) This has important implications, as when we eat plants, genes from the plant are transferred to us through a process called horizontal-gene transfer, which then affects our microbes and our health. (10, 11, 12)
Plants respond to chemicals in the air or on their surface as a form of smell and touch. They react and respond to different shades of light as a form of sight. They can feel vibrations as we have seen in the above studies. The roots, where perhaps much of the plant intelligence is found, will move away from hard objects and share nutrients and space with other roots in very sophisticated ways. Considering that these are only a few examples of the multi-faceted abilities of plants, the traditional view of plants as passive, insensitive life forms seems to be no longer scientifically accurate and it is important to stay open-minded about the possibilities of plants as research continues to explore this intriguing field. (13)
So, next time you accidentally touch the petal of a gardenia and it turns brown, or notice how a vine climbs its way up an arbor towards the sunlight, tune into the secret life of plants and their many intricacies and idiosyncrasies. Plants, when left to do their thing, naturally help us do our thing better. The nature of plants is a primary contributor to the nature of us.