In planta function of compatible solute transporters of the AtProT family

The three proline transporters of Arabidopsis thaliana (AtProTs) transport the compatible solutes proline and glycine betaine and the stress-induced compound γ-aminobutyric acid when expressed in heterologous systems. The aim of the present study was to show transport and physiological relevance of these three AtProTs in planta. Using single, double, and triple knockout mutants and AtProT-overexpressing lines, proline content, growth on proline, transport of radiolabelled betaine, and expression of AtProT genes and enzymes of proline metabolism were analysed. AtProT2 was shown to facilitate uptake of L- and D-proline as well as [14C]glycine betaine in planta, indicating a role in the import of compatible solutes into the root. Toxic concentrations of L- and D-proline resulted in a drastic growth retardation of AtProT-overexpressing plants, demonstrating the need for a precise regulation of proline uptake and/or distribution. Furthermore evidence is provided that AtProT genes are highly expressed in tissues with elevated proline content—that is, pollen and leaf epidermis

Impact of Stomatal Density and Morphology on Water-Use Efficiency in a Changing World

Global warming and associated precipitation changes will negatively impact on many agricultural ecosystems. Major food production areas are expected to experience reduced water availability and increased frequency of drought over the coming decades. In affected areas, this is expected to reduce the production of important food crops including wheat, rice, and maize. The development of crop varieties able to sustain or improve yields with less water input is, therefore, a priority for crop research. Almost all water used for plant growth is lost to the atmosphere by transpiration through stomatal pores on the leaf epidermis. By altering stomatal pore apertures, plants are able to optimize their CO2 uptake for photosynthesis while minimizing water loss. Over longer periods, stomatal development may also be adjusted, with stomatal size and density being adapted to suit the prevailing conditions. Several approaches to improve drought tolerance and water-use efficiency through the modification of stomatal traits have been tested in the model plant Arabidopsis thaliana. However, there is surprisingly little known about the stomata of crop species. Here, we review the current understanding of how stomatal number and morphology are involved in regulating water-use efficiency. Moreover, we discuss the potential and limitations of manipulating stomatal development to increase drought tolerance and to reduce water loss in crops as the climate changes

Steuerung und Regelung einer Windenergie-Netzeinspeisung mit doppeltgespeistem Asynchrongenerator

Die vorliegende Arbeit beschreibt die Modellierung eines doppelt gespeisten Asynchrongenerators und die Entwicklung eines Drehzahlreglers. Der Stator der Maschine ist ans Netz angeschlossen, der Rotor wird über pulsweitenmodulierte, stromgeregelte Wechselrichter gespeist. Durch die Einführung eines synchron umlaufenden feldorientierten Koordinantensystems und der Vernachlässigung des Statorwiderstands sind Blind- und Wirkleistung oder die Drehzahl proportional zu den Komponenten des komplexen Rotorstromvektors. Eine Kaskadenregelung, bestehend aus Drehzahl- und Rotorstromregelung, wurde auf einem echtzeitfähigen Steuerungssystem implementiert und getestet.This thesis describes the modeling of a doubly fed induction generator and the design of the control strategy with a speed controller. The stator of the machine is connected to the grid and the rotor circuit is fed by back-to-back PWM current-source converters. By introducing synchronously rotating field coordinates and neglecting the stator resistance, the reactive and active stator power or the speed of the machine are directly proportional to the direct and quadrature components of the complex current vector of the rotor. A cascade control scheme, consisting of speed and rotor current controllers, is implemented and tested on a real-time system

Apoplastic Expression of Yeast-Derived Invertase in Potato : Effects on Photosynthesis, Leaf Solute Composition, Water Relations, and Tuber Composition

In potato plants (Solanum tuberosum), a chimeric yeast-derived invertase gene fused to a 35S cauliflower mosaic virus promoter has been expressed. The protein was targeted to the cell wall by using the signal peptide of proteinase inhibitor II fused to the amino terminus of the yeast invertase. The transformed plants had crinkled leaves, showed a reduced growth rate, and produced fewer tubers. Although in the apoplast of the leaves of the transformed plants the content of glucose and fructose rose by a factor of 20, and that of sucrose declined 20-fold, 98% of the carbohydrate in the phloem sap consisted of sucrose, demonstrating the strong specificity of phloem loading. In the leaf cells of the transformed plants, glucose, fructose, and amino acids, especially proline, were accumulated. Consequently, the osmolality of the cell sap rose from 250 to 350 mosmol/kg. Our results show that the observed 75% decrease of photosynthesis is not caused by a feedback regulation of sucrose synthesis and is accompanied by an increase in the osmotic pressure in the leaf cells. In the transformed plants, not only the amino acid to sucrose ratio in the phloem sap, but also the amino acid and protein contents in the tubers were found to be elevated. In the tubers of the transformed plants, the protein to starch ratio increased

Bootstrapped Neighbour-Joining Tree Generated from an Alignment of the Predicted 56 AtSBT Full-Length Protein Sequences

<p>Groups of neighbouring genes (e.g., At3g46840 and At3g46850) are distinguished by specific colours.</p