Talking to plants

[newtron]

I just watched an old Mythbusters episode where they tested to see if talking to plants does improve their growth. Their experiment seemed to be well designed. They had several greenhouses under identical conditions with a cassete player playing either recorded voices or music continuously. They expeimented with different voice tones (nice or mean) and different types of music. The result showed that the control group that grew in silence produced the least amount of vegetable matter and the smallest pea pods. The plants subjected to loud death metal did the best. They did admit that their sample size was not big enough to come to any concrete conclusions, but the the results were intriguing.

My theroy is that sound, which is vibrations in the air actually moved air around and acted as a fan and mixed the air so that is was easier for plants to take up CO2. In a perfectly sttill environment with no air currents, CO2 tranport to the leaves would be controlled by diffusion wich is a very slow process.

Any other ideas?

[NetSquirrel]

A good theory. Perhaps it is not so much the gases in the air being "mixed" by vibration that might increase a plant's gas exchange rate, but the sound waves themselves causing small localised regions of high and low pressure in the vicinity of the leaf stomata. I imagine that the alternating high/low air pressure waves of a deep, pounding beat could cause tiny air currents to flow at a leaf's surface. Such currents would theoretically allow for faster gas exchange to occur into and out of the leaf, allowing the plant to respire faster and therefore grow faster and healthier.

[eifionlewis]

There are so many possibilities to explain this though, such as perhaps the air flow increased the rate of transpiration, (air travelling over stomata increases rate of evapotranspiration and so on...).

I think the effect of this would be very small though, and not enough to cause a difference in seed growth etc. I read an article about this not long ago, which completely refuted the claims, stating poor experimental design and subjective thinking.

Personally, i think if there was any effect of the soundwaves on palnt growth it would be the opposite. Vibration can present a mechanical stress on the plants, which then initiates defensive mechanisms. Long story short.... wound-based defense mechanisms can lead to crosslinking of cell wall proteins, which severely limits cell expansion. A study currently underway i nmy department by one of the PhD studies has data confirming this, although it has not yet been published so i can't share it unfortunately. Suffice to say there is a huge difference in plant growth and development in a range of parameters, and i would imagine this would be true of fruits too.

Perhaps sound below a maximum number of decibels may not be enough to cause stress, but may be enough to do something to promote development. An interesting post i saw on a forum said that it could be that the music had more of an effect on the greenhouse workers and made them look after the plants better!

I think the best study would be to look at gene expression and metabolite levels that are related to active plant growth. These would be better parameters to be measured than fruit size and plant growth etc. It may reveal much more convincing evidence, particularly metabolites. Conversely you may see absolutely no difference, and it would leave the question open once again! (Funding may be a problem for this sort of work though, as in a natural growing enviromnent, you arent gonna be playing heavy metal

[eifionlewis]

to a field full of peas!!!