Editorial: Mechanical Signaling in Plants: From Perception to Consequences for Growth and Morphogenesis (Thigmomorphogenesis) and Ecological Significance

Plant morphogenesis and its regulation have fascinated researchers for more than two centuries. Among determinants of morphogenesis mechanical signals appear as an important cue. The fact that plants respond to mechanical stimuli was reported by Darwin in the 1850's. As described by Iida in this research topic, mechanical stimuli were used in traditional agriculture practices like mugifumi. In the past 40 years, the study of mechanical signaling in plants has regained interest because of its implication in fundamental processes of organo-and morphogenesis and their potential as an innovative means of controlling plant growth. The focus of this research topic is the quantification of mechanical signals and of their effects on plant growth, the ecological significance of mechanoperception and thigmomorphogenesis, and the potential use of mechanical stimuli in agriculture practices. The papers in this research topic summarize the current state of knowledge, present new experimental results, identify areas where further investigation is warranted, and propose investigative protocols. Mechanical signals can come from internal forces due to turgor pressure or externally from the environment. In natural conditions, aerial portions of plants experience mechanical stimuli due to wind, snow and rain, while aquatic plants experience water flow, waves or tides. Plants perceive, transduce respond physiologically to mechanical signals, collectively referred to as thigmomorphogenesis. Thigmomorphogenesis has been described in herbaceous as well as woody plant species. In growing shoots and roots, the first response observed after a mechanical signal is perceived is a transitory growth cessation followed by a progressive recovery of elongation rate and an increase of radial growth rate. When repeated mechanical signals are applied, the classical thigmomorphogenetic growth response of aerial plants is a reduced elongation of axes and, for plants which exhibit an active cambial growth, an increase of growth in girth. Thigmomorphogenesis in aquatic plants has been less well examined. This research topic includes two articles on mechanosensing in aquatic plants. Schoenlynck et al. examine the response of the aquatic plant Egeria densa to hydrodynamic stress and describe