Nitrate is both a nutrient and a potent signal that stimulates plant growth. Initial experiments in the late 1950s showing that nitrate enhances nitrate reductase (NR) activity after several hours of treatment have now progressed to transcriptome studies identifying over 1000 genes that respond to muM levels of nitrate within minutes. The use of an Arabidopsis NR-null mutant allowed the identification of genes that respond to nitrate when the production of downstream metabolites of nitrate is blocked. Further dissection of the nitrate response is now possible using new bioinformatic tools such as Sungear to perform comparative studies of multiple transcriptome responses across different laboratories and environmental conditions. These analyses have identified genes and pathways (e.g. nitrate assimilation, pentose phosphate pathway, and glycolysis) that respond to nitrate under a variety of conditions (context-independent). Most of these genes and pathways are ones that were identified using the NR-null mutant as responding directly to nitrate. By contrast, other processes such as protein synthesis respond only under a subset of conditions (context-dependent). Data from the NR-null mutant suggest these latter processes may be regulated by downstream nitrogen metabolites.

The NYU Media Research Laboratory has developed a single-person, non-invasive, active autostereoscopic display with no mechanically moving parts that provides a realistic stereoscopic image over a large continuous viewing area and range of distance [Perlin]. We believe this to be the first such display in existence. The display uses eye tracking to determine the pitch and placement of a dynamic parallax barrier, but rather than using the even/odd interlace found in other parallax barrier systems, the NYU system uses wide vertical stripes both in the barrier structure and in the interlaced image. The system rapidly cycles through three different positional phases for every frame so that the stripes of the individual phases are not perceived by the user. By this combination of temporal and spatial multiplexing, we are able to deliver full screen resolution to each eye of an observer at any position within an angular volume of 20 degrees horizontally and vertically and over a distance range of 0.3-1.5 meters. We include a discussion of recent hardware and software improvements made in the second generation of the display. Hardware improvements have increased contrast, reduced flicker, improved eye tracking, and allowed the incorporation of OpenGL acceleration. Software improvements have increased frame rate, reduced latency and visual artifacts, and improved the robustness and accuracy of calibration. New directions for research are also discussed.

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