TY  - GEN
ID  - heidok7333
Y1  - 2006///
TI  - Transport phenomena in plant-internal processes: growth and carbon dioxide transport
KW  - roots 
KW  -  growth model 
KW  -  transport equations 
KW  -  gravitropism
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/7333/
AV  - public
N2  - Aim of the here presented work was the quantitative modeling of plant-internal processes. Growth of cells and tissues was one of the central themes, although the lateral transport of carbon dioxide (CO2 ) was also treated. These processes depend strongly on fluxes of water, hormones and/or CO2 . Thus, suitable transport equations were sought for to describe these processes. Using the Lockhart-Equations, which are well known in biology to describe the growth of a whole cell, local formulations of energy and mass conservation were obtained. These formulations can be used to determine local growth patterns in cells. This was shown through a numerical example of a spherical cell. Finally, the conservation equations found, were shown to be consistent with the empirical Lockhart-Equations. Plant organs, such as roots and hypocotyls, have spatial and temporal growth patterns. For example, the spatial distributions of growth in primary roots is given by a bell-shaped distribution along the organ axis. This particular one dimensional growth pattern was modeled here through the transport of two hypothetical phytohormones and using the Lockhart-Equations as the underlying growth equations. Because the hypothetical hormones were chosen to have auxin and cytokinin (two of the most important plant hormones) properties, the model stays in a plant physiological context. Not only one dimensional growth patterns are found in roots and hypocotyls. These tend to have organ curvature and torsion, as becomes clear particularly in tropisms (e.g. gravitropism, hydrotropisms and phototropism). Although these processes are known for a long time in biology, no suitable measures to characterize the production of curvature and torsion have been defined. Using a curvature and torsion conservation equation, a measure for their production was found here. These measures were then exemplified in a simple model of the root gravitropic reaction, and applied in the characterization of the gravitropic reaction of Arabidopsis thaliana (L.) Heynh. wild-type and pin3 mutant roots. The gravitropic reaction is believed to be regulated by the hormone auxin. pin3 mutants are deficient in the PIN3 protein, which is essential in the transport of auxin in the root tip. Through comparison of the reaction of wild-type and pin3 roots, it was shown here that the gravitropic reaction is not solely regulated by auxin, so that other regulation mechanisms need to exist. Finally, transport equations were found, which describe the transport and assimilation of CO2 in leaves. Using gas-exchange and chlorophyll fluorescence measurements, the homogenized lateral diffusion coeffcient of leaves was determined. Moreover, the strategy behind the existence of lateral diffusion in leaves was discussed (plants differ in the porosity of their leaves). Throughout the work presented here, it became clear how fructiferous the application of transport equations in biology is. The importance of a quantitative description in biology became also clear. Everyday new questions arise in biology. An answer to these may only be found using an interdisciplinary approach.
A1  - Chavarría Krauser, Andrés
ER  -