A Mechanism for the Origin of Specifically Oriented Textures in Development with Special Reference to Nitella Wall Texture

Abstract

SummaryMany oriented growth phenomena, including the elongation of the Nitella internode, are based upon oriented or textured cell wall structure. In many cases the ordered textures are not present in the earliest stages of cell development but appear later. In Nitella lateral cell (leaf) development the first appearance of transverse wall texture (detected in polarized light) approximately coincides with a transverse stretching of the cell and its wall. This oriented stretching appears not to have its origin in a pre-existing texture but rather to be the result of a particular distribution of wall expansion rates. The relation between rates and oriented distortions is studied as a general phenomenon. The form these rate variations must take to provide longitudinal, transverse, or isotropic distortion is derived. Model devices made of rubber membranes, where expansion rate is varied by reinforcement of the rubber, generate distortions (textures in the rubber) of the type predicted. In the course of development it is possible that imbalances in expansion rate based on gradients (of metabolites, pH, light, etc.) bring on, through strain orientation, the initial alignment of originally randomly oriented fibrous ultrastructures, such as microfibrils of the cell wall or cytoplasmic microtubules.

Computer simulation and mathematical models of the noncentrosomal plant cortical microtubule cytoskeleton

“…In addition to biochemical factors, mechanical forces have been proposed to play a role in orienting CMTs along a particular direction [Green and King, 1966]. Recently, elegant studies using laser ablation and external force application to the shoot apical meristem have provided experimental support for the idea that CMT orientation is responsive to mechanical stress fields [Hamant et al, 2008].…”

Developmental Patterning by Mechanical Signals in Arabidopsis

“…In a multicellular setting, the field of physical forces represents a potential source of information for the cells to know their relative position (7,(26)(27)(28)(29)(30). Several studies have supported the proposal that maximal stress directions orient cortical microtubules, most probably via a response to strain in the cell wall (8,10,(31)(32)(33).…”

“…Members of the solute carrier 6 (SLC6) family of sodium-coupled transporters, also known as neurotransmitter sodium symporters, make up one of the most widely investigated and pharmacologically important classes (4,5). SLC6 proteins play a central role in diverse physiological processes, ranging from the maintenance of cellular osmotic pressure (6) to the reuptake of small-molecule neurotransmitters in the brain (7). SLC6 dysfunction is implicated in numerous debilitating illnesses, such as depression (8), obsessive-compulsive disorder (9), epilepsy (10), autism (11), orthostatic intolerance (12), X-linked creatine-deficiency syndrome (13), and retinal degeneration (14).…”

“…Because this direction is often parallel to the cortical microtubules of the plant cell, it is thought that the microtubules might serve as tracks along which the cellulose synthase complexes travel (5,6). Green and others have proposed that cortical microtubule orientations correlate with anisotropic stresses, but the existence of such a causal link with morphogenesis has never been further investigated (7)(8)(9)(10)(11). We have chosen to dissect this link in shoot apical meristems, a population of stem cells that continuously generate aerial organs while undergoing complex shape transformations (12,13) (fig.…”

The mechanics of tip growth morphogenesis: what we have learned from rubber balloons

“…Therefore, high strain rate (relative to the isotropic solution) near the pole of the cell implies circumferential anisotropy on the flanks of the dome. A similar argument was made by Green and King [1966], who demonstrated the validity of their result using locally reinforced rubber membranes. These statements will be made more precise when we discuss our model in Section 4, but first we look at the kinematics of rubber balloons from which the model was inspired.…”