Some science behind the scenes
Plants are living organisms belonging to the kingdom Plantae and include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and even green algae. The group is also called green plants or Viridiplantae in Latin. They obtain most of their energy from sunlight via photosynthesis using chlorophyll contained in chloroplasts, which gives them their green color.
Precise numbers are difficult to determine, but as of 2010[update], there are thought to be 300–315 thousand species of plants.
Plant cells are typically distinguished by their large water-filled central vacuole, chloroplasts, and rigid cell walls that are made up of cellulose, hemicellulose, and pectin.
And cellulose is a transducer. Cellulose can convert mechanical energy such as sound or movement into electrical energy.
History and recent progress in piezoelectric polymers - Fukada E; Kobeyasi Inst. of Phys. Res., Tokyo, Japan.
Electrets of carnauba wax and resin have exhibited good stability of trapped charges for nearly 50 years. ….. Since the 1950s, shear piezoelectricity was investigated in polymers of biological origin (such as cellulose and collagen) as well as synthetic optically active polymers (such as polyamides and polylactic acids).
This same electric current helps the plant to grow. It is not a myth that sound delivered to plants has no effect – it does.
A ‘MythBusters’ experiment showed plants exposed to sound recordings actually growing faster than the control subject but reacting to sound intensity and shape regardless of the recordings content. The experiment worked equally well with kind or angry talk, better with classical music and even better with death metal. This simply shows that sound induces electric current – it says nothing for the plants’ taste in music!
In the outdoors, the plants are mechanically stimulated by the wind and wind helps a plant grow by inducing current, so a windy garden is not necessarily a bad thing.
In a greenhouse, plants may actually benefit from being played low intensity sound. Just like a human being low intensity sound appears to promote growth whereas high intensity sound damages in the long term and in particular it appears to damage the genes of plants.
A study on differentially expressed gene screening of Chrysanthemum plants under sound stress. - Hongbo S, Biao L, Bochu W, Kun T, Yilong L; Institute of Soil and Water Conservation, Chinese Academy of Sciences, Northwest A&F University, Yangling China.
Environmental stress can induce differential expression of genes of flower plants.
It has been found that sound stimulation has an obvious effect on the growth and development of flower plants, but it is not reported on the differentially expressed genes and their expressing characteristics under sound stimulation.
This is one of the few reports in terms of using the DDRT-PCR technique for screening the differentially expressed cDNA fragments responding to sound-wave stress on Chrysanthemum.
Six differentially expressed cDNA fragments were obtained. Molecular weight of fragments was from 200 to 600 bp, respectively. Among differential fragments acquired, three of them (SA3, SG7-1, and CA2) were found to be positive fragments by northern dot hybridization, whose molecular weight are 270, 580 and 370 bp, respectively. SA3 was differentially expressed and SG7-1 was preferably expressed, while CA2 was restrained by the sound wave.
These results indicated that expression of some genes was turned on, meanwhile the stress restrained some genes from expression under the mode of sound-stress stimulation.
The Chinese in particular are doing a great deal of research on this area at the moment – the effect of sound on plants, but not the effect of manipulation. I believe that cleaning a plant’s leaves and stroking it or bending it gently may also help promote growth. The effects of rain [more mechanical stimulation] may also have a positive effect, which means that watering plants in a greenhouse should be done via a reasonably powerful sprinkler system, not by irrigation.
Effect of polysaccharides content of tissue culturing seedlings on Dendrobium candidium under sound wave stimulation] - [Article in Chinese] - Li B, Wang BC, Liang YL, Tang K, Shu KX, Liu WQ.; - Key Laboratory for Biomechanics and Tissue Engineering under the State Ministry of Education, College of Bioengineering, Chongqing University, China.
To detect the polysaccharides content of tissue culturing seedlings on Dendrobium candidium under special sound wave stimulation.
The content of polysaccharides was detected by phenol-vitriol colorimetry method.
The polysaccharides content of the groups stimulated continuously for 24d was higher obviously than the content of the control groups.
The stimulation of the special sound wave promoted markedly the synthesis of polysaccharides in D. candidium. It may affect obviously the metabolic pathway of polysaccharides in D. candidium.
Proof that an electric current is generated was provided back in the 1960s by Clive Backster. Clive Backster was a US policeman and used lie detectors in his job.
The following description of his ‘findings’ is not atypical………………….
Internet site describing Beckster’s findings
The year was 1966 and Backster had had a long day on this particular eventful day. It was late evening and he had just finished teaching his last class to a group of NYC cops, who wanted to learn his techniques. As he sat alone in his office he looked over at his tropical plant, the dracaena, and was overcome with an impulse. He had never done it before, was not a horticulturalist, and had no reason to do what he did.
Backster moved from behind his desk and attached a set of electrodes from one of his lie detectors to the palm-like leaf of the dracaena plant. He then poured water into the plant's pot and watched his lie detector to see if there was a reaction. Backster expected his lie detector to show less resistance as the plant sucked up the water. A moister plant should conduct more electricity. To his surprise, however, the pin of the detector, instead of tracing upward, traced downward. His jaw dropped to the floor, metaphorically speaking, of course. His plant produced the same kind of tracing a human produces when experiencing a short emotional burst. Was the plant happy to have had a drink? What started as an impulse now took on conscious intent.
Backster decided to ratchet things up. He knew that in order to get the galvanometer to really jump for a human required a threat to their personal integrity. He tried to reproduce a jump in the galvanometer by dunking the plant's leaf in his cup of hot coffee. Nothing happened. Backster determined that the threat was not strong enough and decided to burn the leaf to which the electrodes were attached. To his utter amazement the pin of the lie detector displayed a long upward swing before he could even get his hand on some matches. It was as if the plant perceived his thoughts and reacted to what was about to happen. He left the room to fetch some matches, intent on carrying out his plan. When he approached the plant it again produced the same upward deflection of the pin. When he actually burned the leaf he got a slightly lower reaction on the graph.
Now, too many conclusions have been drawn from very simple evidence that plants produce an electric charge. The lie detector simply measured that a plant produces an electric charge – that is all.
If you water a plant it induces mechanical change and that mechanical change will itself - by transduction – produce an electric current. Thus water and the electric current will then help the plant to grow.
Dunking the plant’s leaf in a hot coffee is a mechanical action, but may not have been done with enough energy to induce an electric current.
But what we do not know is what sounds were being made as Clive then decided to burn the leaf. He is walking about getting matches, so sound is being made, but is he talking to himself ? He’s a policeman - he is probably a big bloke with big boots!! We don’t know, but of course there are those who desperately want to believe a plant has emotions who will say, no no it responded to a threat. My view is that it responded to sounds.