Morphological responses of plant roots to mechanical stress

Abstract

Several modifications in root morphology are commonly reported: (1) decreased root size, (2) radial swelling accompanied by increased radial dimension of the cortex cell layers and (3) enhanced cap cell sloughing. Nevertheless, because of differences between species and individual plants, a universal scenario for root morphological changes resulting from externally applied pressures is not possible. Thus, knowledge of the root response to mechanical impedance remains incomplete. Studies on the mechanical properties of the root as well as on possible modifications in cell wall structure and composition as the elements responsible for the mechanical properties of the plant tissue are required to understand the response of root tissue as a biomaterial.

The botanical multiverse of Peter Barlow

“…Whilst this isn't plant neurobiology, the notion of cell wallfacilitated 'communication' between plants is an interesting example of how seemingly disparate aspects of plant biologyin this case cell wall chemistry and plant-plant communicationcome together and contribute to a more holistic appreciation of plant behaviour. And, as we've already seen with the work of Potocka and Szymanowska-Pułka [93] and Dreyer and Edelmann [94] in the SIAB, ethylene is fast becoming one of the most important and topical of the classical plant hormones [95].…”

“…Potocka and Szymanowska-Pułka's review [93] the morphological responses of plant roots to mechanical stresses. Several modifications in root morphology are known: decreased root lengths; radial swelling of root apices; and enhanced sloughing of root cap cells.…”

Lateral mechanical impedance rather than frontal, promotes cortical expansion of roots

“…Considerable evidences have amassed to indicate that mechanical impedance can reduce the elongation and promote the radial expansion of roots [1,4,5,10]. Nevertheless, all previous studies on mechanical impedance have obtained data from plants in which the entire root system has been embedded by various substrates, such as glass beads, soil, sand, and phytagel [1,3–5,10]. In these studies, it was not possible to distinguish the effects of frontal and lateral impedance, and consequently, root shortening and thickening always appeared concurrently.…”

“…The growth of roots in soil can be limited by the physical, chemical, and biological properties of soil, among which physical properties have been reported to be most strongly linked to root elongation [1–3]. In terms of the physical limitations on root growth, mechanical impedance (caused by soil that is too compact to enable rapid root penetrance) mainly affects root systems by hindering root elongation and concurrently promoting root thickening [1,3,4]. Soil is a dense medium, and it is necessary for root tips to generate sufficiently mechanical force to penetrate through the soil in the absence of continuous pores of a sufficiently large diameter [1,5].…”

“…Actually, mechanical impedance of soil can be classified into frontal- and lateral-type based on the position of root, and frictional (lateral) impedance between roots and the soil may account for up to 80% of total mechanical impedance [4,9]. All previous studies on mechanical impedance have obtained data from plants in which the entire root system has been embedded in various substrates, such as glass beads, soil, sands, and phytagel [1,3–5,10]. In these studies, it was not possible to distinguish the effects of frontal and lateral impedance.…”