ALBERT

Description: The conduct of Life Science experiments aboard the Shuttle Spacelab presents unaccustomed challenges to scientists. Not only is one confronted with the challenge of conducting an experiment in the unique microgravity environment of a orbiting spacecraft, but there are also the challenges of conducing experiments remotely, using equipment, techniques, chemicals, and materials that may differ from those standardly used in ones own laboratory. Then there is the question of "controls." How does one study the effects of altered gravitational fields on biological systems and control for other variables like vibration, acceleration, noise, temperature, humidity, and the logistics of specimen transport? Typically, the scientist new to space research has neither considered all of these potential problems nor has the data at hand with which to tackle the problems. This paper will explore some of these issues and provide pertinent data from recent Space Shuttle flights that will assist the new as well as the experienced scientist in dealing with the challenges of conducting research under spaceflight conditions.

Description: A widely tunable infrared spectrometer based on difference frequency generation (DFG) has been developed for organic trace gas detection by laser absorption spectroscopy. On-line measurements of concentration of various hydrocarbons, such as acetylene, benzene, and ethylene, were investigated using high-resolution DFG trace gas spectroscopy for highly sensitive detection.

Description: Biophysical parameters related to gibberellin (GA)-dependent stem elongation were examined in dark-grown stem-length genotypes of Pisum sativum L. The rate of internode expansion in these genotypes is altered due to recessive mutations which affect either the endogenous levels of, or response to, GA. The GA deficient dwarf L181 (ls), two GA insensitive semierectoides dwarfs NGB5865 and NGB5862 (lka and lkb, respectively) and the slender' line L197 (la crys), which is tall regardless of GA content, were compared to the wild-type tall cultivar, Torsdag. Osmotic pressure, estimated by vapor pressure osmometry, and turgor pressure, measured directly with a pressure probe, did not correlate with the differences in growth rate among the genotypes. Mechanical wall properties of frozen-thawed tissue were measured using a constant force assay. GA deficiency resulted in increased wall stiffness judged both on the basis of plastic compliance and plastic extensibility normalized for equal stem circumference. Plastic compliance was not reduced in the GA insensitive dwarfs, though lka reduced circumference-normalized plasticity. In contrast, in vivo wall relaxation, determined by the pressure-block technique, differed among genotypes in a manner which did correlate with extension rates. The wall yield threshold was 1 bar or less in the tall lines, but ranged from 3 to 6 bars in the dwarf genotypes. The results with the ls mutant indicate that GA enhances stem elongation by both decreasing the wall yield threshold and increasing the wall yield coefficient. In the GA-insensitive mutants, lka and lkb, the wall yield threshold is substantially elevated. Plants possessing lka may also possess a reduced wall yield coefficient.