Sound is a wave and music is a specific kind of melodious sound. These waves capable of moving through elastic media are characterized by specific frequencies. Plants being living organisms get affected by external stimuli. Many researchers have used sound wave frequencies as external stimuli and studied their effect on plants. Collins and Foreman subjected beans and plants to different frequencies (5000 Hz, 6000 Hz, 12000 Hz, and 14000 Hz).
Under similar environmental conditions favorable for plant growth, the plants were kept inside a chamber and the sound waves were directed towards them. The process of speaker diaphragm moving back and forth generated a wave in the vicinity in air medium. Compression portion of the wave generated increased pressure and rarefaction generated reduced pressure and this propagated along the surface of the leaves creating a scrubbing or brushing action on the leaf surface. This helped in removal of the moisture film and facilitated the leaf to breathe or transpire better. Most favorable growth was observed in both beans and the plants when the wavelength of the sound played matched with the dimension of the leaf of the plant. Xiujuan and team reported that sound wave level of transcription and in accelerated the synthesis of turn promoted better growth. Metabolism in plants can be greatly affected by music.
Plants are reported to behave differently to different music types and frequency. Sternheimer, a French physicist and musician, has framed melodies that apparently help plants grow. The notes are designed on the basis of the quantum vibrations that occur at the molecular level as a protein is being assembled from its constituent amino acids. Length of a note correspond to the real time that is taken by each amino acid to come after the next. Thus, on playing the appropriate tune, production of protein increases in the plant and hence, its growth is stimulated. Sternheimer remarked that tomatoes exposed to such tunes grew two and a half times better than the control ones; even virus growth in tomato plants could be stopped by playing tunes that inhibited enzymes essential for it.
Growth rate in terms of height and biomass respectively increased by 20% and 72% when treated with classical music, i.e. raga music played on Indian musical instruments like flute, violin, and harmonium. Similar positive effect was observed in field crops - like size increment in the range of 25% to 60% above other regional crops. Petunias and marigolds were found to flower two weeks before the scheduled time when exposed to the rhythm of bharatnatyam, an ancient Indian classical dance style
Cai et al., exposed mung bean (1000–1500 Hz, 1500–2000 Hz, and 2000–2500 Hz, and measured their development in terms of mean germination time, length and weight of the stem and root that developed from the bean. They reported significant reduction of germination time and increase in growth of the seedlings when exposed to frequency of 2000 Hz and intensity of 90 dB .
Plant Acoustic Frequency Technology (PAFT) uses an acoustic frequency generator to produce appropriate acoustic wave that is similar to the frequency of the specific sound of the plant itself. It has been reported that if the applied frequency resonates with the plant‟s natural frequency, then rate of photosynthesis and cell division increases leading to faster growth of plant and hence fruit bearing time for the plants under resonant frequency treatment is reached before the control plants. Experiments performed with sweet potato, cucumber and tomato indicated the improvement of crop quality and enhanced disease resistance capacity. The yields of sweet potato, cucumber and tomato exposed to the specific frequencies were 63.05%, 67.1% and 13.2% higher than those of the control group.
Chemical fertilizers and pesticides are hazardous for plants and in turn for the human population who consumes their product. Various studies have shown the positive effect of sound waves including music on various plant parts which ultimately led to a better and healthy yield of plants. Based on the exposure time, sound pressure levels and frequencies plants, in general, showed a positive growth trend and better immune system. Low frequency sound is known to activate enzymes, increase cell fluidity and enhance other growth parameters like DNA replication and cell cycling.
Dorothy Retallack (Author of the sound of music and plants) conducted severals experiments to observe the effect of music of different types of plants and infared music as a positive factor for growth. Classical music of specific frequency, interval and rhythm accompanied with dynamically changing lyrics positively influenced root growth and mitotic division in onion plants. Mi-Jeong and co-workers played 14 different classical music pieces including Beethoven‟s music to rice plants and monitored gene expression. Audible sound at frequencies 125Hz and 250Hz made genes more active for the process of DNA code translation into biological processes like growth.
Conclusion: Summing up all the experimental observations of various workers, it can be stated that specific audio frequencies in the form of music facilitated the germination and growth of plants, irrespective of the music genre.The increased rate of growth in terms of more flowers, leaves, buds etc. suggests that specific audible frequencies including music can benefit the agricultural sector by increasing the productivity. Simultaneously, this might reduce the requirement of toxic chemical fertilizers and pesticides and thus, reduce environmental pollution and facilitate the well-being of plants, animals and human beings. There is a wide scope to carry out further research in this interdisciplinary domain wherein physicists, biologists and agricultural engineers can get actively involved to devise a scheme to nurture this green way of agriculture.