here are two foci of activity in my laboratory: (1) a long-standing interest in the acquisition of nitrogen by plants; (2) developing libraries of computer-individualized homework problems in plant physiology and general biology for use with networked-based learning tools. We seek excellent graduate students for these projects.

We previously focused on formation of "leghemoglobins", the abundant hemoproteins essential for nitrogen fixation in the Rhizobium-legume root nodule symbiosis (Verma and Nadler, 1984; Nadler et al, 1990). We now have initiated a genetic and physiological study of the mechanism by which plants adapt to the availability of 'combined nitrogen'. N availability profoundly affects plant growth, development and ultimately productivity. Nitrogen deficiency stunts growth of the shoot and leaves, and the development and function of chloroplasts; yet enhances root growth, branching and other root activities. These latter responses are regarded as a strategy to enhance the mining, uptake and metabolism of scarce soil nitrogen. We seek the mechanism by which nitrogen-limited Arabidopsis thaliana senses available nitrogen. We developed convenient methods to 'up-shift' and 'down-shift' these plants with respect to available N. RNA from metabolically shifted plants can be used to generate probes to A. thaliana microarrays, to identify highly regulated genes.

Information technology can be used in a variety of ways to improve instruction in biology. We use CAPA, a networked teaching and learning tool to generate computer-individualized homework problem sets for classes in plant physiology (Artus and Nadler, 1999) and non-major biology. We achieve significant improvement in student examination performance as a result of these regular assignments, with CAPA being an effective and efficient substitute for hand-graded homework. We continue to expand our libraries of CAPA formatted problems in biology and plant physiology.