Ensembles of the leaf trichomes of Arabidopsis thaliana selectively vibrate in the frequency range of its primary insect herbivore

Selective sensation of sound by the plant Arabidopsis thaliana may enable the timely upregulation of defensive compounds to protect against caterpillars of the plant's primary insect herbivore. Vibration of leaf trichomes has been shown to occur over frequency ranges that are appropriate for responding to these caterpillars, but the distribution of trichome shapes and sizes over a leaf means that a range of sounds could possibly be transduced. To assess how the diversity of trichomes on a leaf may affect sound transduction, we characterized the distribution of trichome sizes on a mature plant of A. thaliana and calculated the ensemble responses of entire leaves. Trichome sizes followed a normal distribution. Modal peaks in single trichome response spectra were at lower frequencies those of larger trichomes, roughly consistent with an inverse relationship between modal frequencies and trichome size. Ensemble response spectra for entire leaves showed frequency bands of responsiveness separated by defined band gaps, suggesting a possible mechanism for collective identification of the sounds of specific caterpillars.