Ancient people of India knew much before. Old persons used to say that if you talk to trees, they will yield more fruits. Unfortunately these were labelled as superstitions by western educated persons. In fact Indian scriptures talk about environment. There was tradition that when ever a child was born two mango saplings were planted. The reason being that when child becomes adult he will get to eat mangoes and when he or she dies the mango tree is used for cremation.
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I too feel it could be true . Some experiments conducted in the Annamalai University showed that harmonic sound waves affect the growth, flowering, fruiting and seed yields of plants. After all whatever good attention we pay towards plant is a form a wave and its good or bad effect could easily be felt as response from the other side .