Mythbusters - Talking to plants - part2

Seven small greenhouses were set up on the M5 Industries roof. Four were set up with stereos playing endlessly looping recordings (as having the MythBusters actually talk to the plants could contaminate the samples with their expelled carbon dioxide): Two of negative speech, two of positive speech (Kari and Scottie each made one positive and one negative inducing soundtrack), a fifth with classical music and a sixth with intense death metal music. A seventh greenhouse, used as a control sample, had no stere