Abhängigkeit des Wurzelwachstums vom Lichtregime des Sprosses und deren Modifikation durch Nährstoffe sowie im Gravitropismus

Nagel, Kerstin A.

Dissertation / PhD Thesis/Book

Abhängigkeit des Wurzelwachstums vom Lichtregime des Sprosses und deren Modifikation durch Nährstoffe sowie im Gravitropismus

Nagel, K. A. (Corresponding author)FZJ*

2006
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 3-89336-443-9

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Reihe Umwelt / Environment 63, 119 S. (2006) = Universität Düsseldorf, Diss., 2006

Please use a persistent id in citations: http://hdl.handle.net/2128/2481

Abstract: The aim of this Ph.D. thesis was to characterise the effects of light, also in combination with nutrient availability or gravitropic response, on the growth dynamics of Nicotiana tabacum. Seedling biomass, primary root growth as well as sugar concentration in root and shoot increased significantly with increasing light intensity (60 to 300 μmol m$^{-2}$ s$^{-1}$). To quantitatively analyse the dynamics of root growth a digital image sequence processing method with a high temporal and spatial resolution was applied. Upon transition from low to high light intensities, root growth increased continuously within four days, reaching the steady-state level measured in plants that had been cultivated in high-light conditions (300 μmol m$^{-2}$ s$^{-1}$). The entire root growth zone, and hence each phase of cellular development, was affected very similarly by the increasing light treatment. During the first three hours after light increase, strong growth fluctuations were observed repeatedly. While the first phase of the reaction (0.5 h) could be attributed to hydraulic acclimation, the second phase (2.5 h) could be ascribed to photosynthetic acclimation. Experiments with externally applied sucrose and with transgenic plants having reduced capacities for sucrose synthesis indicated clearly that increasing light intensity rapidly enhanced root growth by enhancing sucrose export from shoot to root. High light intensity facilitated increasing lateral root production under nutrient deficiency some days earlier than low light conditions. This demonstrates the tight and coordinated interaction between carbohydrate and nutrient metabolism. By using two Arabidopsis mutants, in which auxin-mediated signaling is impaired, two spatially separated zones and motors of curvature production in root tips were revealed after rotating the plants by 90°. Only the second motor, which is located more basal, seems to be auxin dependent. The increase of curvature production of this motor after light changing may be attributable to an increase of the energy-dependent auxin-transport or to an enhancement of circumnutation frequency. Due to the circumnutations, leading to a transient curvature in the opposite direction of gravitropic force, roots exhibited under low and high light intensity 2.5 h after rotation by 90° comparable curvature angles.

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