Arabidopsis Leaf Trichomes as Acoustic Antennae Shaobao Liu, Jiaojiao Jiao, Tian Jian Lu, Feng Xu, Barbara G. Pickard, Guy M. Genin  Biophysical Journal  Volume 113, Issue 9, Pages 2068-2076 (November 2017) DOI: 10.1016/j.bpj.2017.07.035 Copyright © 2017 Biophysical Society Terms and Conditions

Figure 1 Structures of natural and simulated Arabidopsis trichomes. (a) Given here is a UV microscopy image, showing interior wall taper. The bar is 20 μm. (b) Given here is a confocal microscopy image of a trichome stained with a pH bioreporter, tilted by compression from above. This image illustrates some of the considerable morphological variation that occurs, which was compensated by evaluating image stacks of trichomes with differing shapes. (c) Given here is a 3D illuminated rendering of the aerial portion of a trichome. (a and b) Reprinted with permission from Zhou et al. (2). To see this figure in color, go online. Biophysical Journal 2017 113, 2068-2076DOI: (10.1016/j.bpj.2017.07.035) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 2 Schematic of a model to predict the order of magnitude of the natural frequency for torsional oscillations occurring about the trichome stalk axis. Biophysical Journal 2017 113, 2068-2076DOI: (10.1016/j.bpj.2017.07.035) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 3 The first eight mode shapes for an archetypal trichome. The lowest mode involved torsion about the stalk axis, and the next modes involved flexure and distension of the stalk. In higher modes, flexure of the branches was observed. Modal shapes are better visualized through animations provided in Movies S1, S2, S3, S4, and S5. To see this figure in color, go online. Biophysical Journal 2017 113, 2068-2076DOI: (10.1016/j.bpj.2017.07.035) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 4 The lowest vibrational mode was torsional for the baseline parameters of the archetypal trichome (dashed vertical line: baseline Young’s modulus). The character and natural frequency for the first mode were largely insensitive to Young’s modulus over approximately two orders of magnitude in the vicinity of the baseline Young’s modulus. For very low Young’s modulus, the first mode switched from the torsional mode to the flexural mode shown in position (A). To see this figure in color, go online. Biophysical Journal 2017 113, 2068-2076DOI: (10.1016/j.bpj.2017.07.035) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 5 The mechanics of the leaf foundation was a strong determinant of the lowest natural frequency of the trichome. High compliance caused a switch from the torsional vibration mode to a rocking mode. The baseline parameters (dashed vertical line) provided a peak in the frequency, indicating that subtle changes such as pH-induced compliance could be used to trigger enhanced sensitivity to low frequency acoustic signals. To see this figure in color, go online. Biophysical Journal 2017 113, 2068-2076DOI: (10.1016/j.bpj.2017.07.035) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 6 The natural frequencies of the archetypal trichome decreased with decreasing turgor pressure. (Vertical dashed line) Baseline parameters. To see this figure in color, go online. Biophysical Journal 2017 113, 2068-2076DOI: (10.1016/j.bpj.2017.07.035) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 7 Effects of cell wall taper on the natural frequency of a trichome. The choice of model for the wall taper affected frequencies by up to a factor of 2, but did not affect trends. To see this figure in color, go online. Biophysical Journal 2017 113, 2068-2076DOI: (10.1016/j.bpj.2017.07.035) Copyright © 2017 Biophysical Society Terms and Conditions