No abstract

The much studied plant Arabidopsis thaliana has been reported recently to react to the sounds of caterpillars of Pieris rapae chewing on its leaves by promoting synthesis of toxins that can deter herbivory. Identifying participating receptor cells-potential "ears"-of Arabidopsis is critical to understanding and harnessing this response. Motivated in part by other recent observations that Arabidopsis trichomes (hair cells) respond to mechanical stimuli such as pressing or brushing by initiating potential signaling factors in themselves and in the neighboring skirt of cells, we analyzed the vibrational responses of Arabidopsis trichomes to test the hypothesis that trichomes can respond acoustically to vibrations associated with feeding caterpillars. We found that these trichomes have vibrational modes in the frequency range of the sounds of feeding caterpillars, encouraging further experimentation to determine whether trichomes serve as mechanical antennae.

It has been reported that Arabidopsis thaliana leaf trichome can act as a mechanosensory switch, transducing mechanical stimuli into physiological signals, mainly through a buckling instability to focus external force (e.g., exerted by insects) on the base of trichome. The material and structural properties of trichomes remain largely unknown in this buckling instability. In this report, we mainly focused on material standpoint to explore the possible mechanism facilitating the buckling instability. We observed that the Young's modulus of trichome cell wall decreased gradually from branch to the base region of trichome. Interestingly, we also found a corresponding decline of calcium concentration on the trichome cell wall. Results of finite element method (FEM) simulation suggested that such a gradient distribution of Young's modulus significantly promotes force focusing and buckling instability on the base of trichome. It is indicated that Arabidopsis trichome has developed into an active mechanosensor benefiting from gradient cell wall mechanical properties.

Nature has inspired mankind to create novel inventions with biomimetic structures and materials, where plants provide a significant source of inspiration. Plants have evolved a range of effective appendages, among which trichomes have attracted extensive research interest due to their enormous functions. It is important to understand trichome functions and corresponding mechanisms for their bioinspired applications. In this review, we provide a comprehensive overview of the diverse functions of trichomes, with emphasis placed upon their roles as biophysical barriers that can create a complex three-dimensional (3D) network to help the plant adapt to severe environments. Moreover, we also summarize the bioinspired applications of four typical trichomes, including needle-like, hook-like, foliar-like, and antenna-like trichomes. This review offers a new perspective of interdisciplinary research on both trichome functions and their biomimetic applications.