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It is hypothesized that the weightless environment experienced during space flight has a stimulating effect on the growth rate of microorganisms. This theory was tested with the bacterium Escherichia coli using protocols and supporting hardware evolved over five space shuttle missions between April, 1991 and July, 1993. In comparing 38 bacterial growth experiments across multiple flights, the overall average population density of E. coli achieved in space was 88% greater than that of matched ground controls (N=19 flight, 19 ground, p < 0.05). Depending on test variables, growth increases in space of up to 257% over ground controls were observed. Analysis of bacterial proteins by gel electrophoresis indicated an apparent difference in expressed protein between flight and ground control E. coli samples in the range of 20-30 kD.

This study investigated the possibility of detecting water deficit stress in plants by using optical signals collected from leaves. Two theoretical approaches have been investigated. In principle, chlorophyll fluorescence can be used to measure generally stressful situations in plants. Our review, however, found that simple ratios of coarsely time-resolved chlorophyll fluorescence, such as maximum fluorescence over fluorescence at steady state, appear to be incapable of adequately distinguishing water stress from other stress factors. A second principle being investigated involves correlation of light absorption within leaves to leaf-water-content using water absorbing and non-water absorbing wavelengths. Our investigation concentrated on defining and eliminating as many extraneous variables as possible.