Joseph A. Turner
Date of this Version
Keynia, S. (2019). Multi-layer Anisotropic Growth Model for Plant Trichome Branches. Unpublished master's thesis). The University of Nebraska, Lincoln, US.
Arabidopsis (Arabidopsis thaliana) leaf trichomes are unicellular structures with a well-studied development. However, little is still known about their mechanical properties because of their size and position relative to other epidermal cells. Thus, common methodologies for the measurement of mechanical properties are nearly impossible to use. One approach that has been used to validate the mechanical properties of 3D finite element (FE) models is to validate their consistency with respect to measurements in order to reduce the possible combinations of mechanical properties that lead to realistic morphology. Here, a combination of live-cell imaging and finite element computational modeling of trichome branches is used to determine how microtubules control cellulose deposition to pattern the cell wall architecture during growth. Live imaging techniques, which provide dynamic images of microtubule alignment and cellulose orientation simultaneously with growth, can provide significant information about the cellular texture of each branch. In this way, the cellulose orientation and organization within the wall can be studied with respect to measured behavior. In particular, the direction of the trichome branch twist is examined for both FE models and real branches after desiccation to remove the turgor pressure. The twist shows an asymmetry inwall organization with a dominant directionality for the wild-type plants. A range of plausible values for wall properties and cellulose fiber organization is determined through a combination of observations and FE modeling. Finally, a multi-lamellar FE model is developed to simulate trichome growth using modeling scripts that are integrated with the FE model. The properties and appropriate organization of the lamellae are found, that are consistent with the growth pattern of trichome branches as well as their collapse upon desiccation. This growth model is also used to match the branch shape for several genetic mutants with different morphologies. The orientation of the lamellae with respect to the growth axis has a profound impact on the overall branch shape. Such an approach is expected to lead to new insights into the morphogenesis of plant cell walls.
Advisor: Joseph A. Turner