Slide 12 of the powerpoint file shows a graph showing anticipated results for a 50 kPa vs 100 kPa. The title block indicates there might be investigations for 10, 25, 50, and 75 kPa vs 100 kPa. So basically there may be tests of plant growth in as little as 1/10th of an atmosphere of pressure.

These investigations are under the umbrella of "Functional Genomics Research Grants", which is described quite well by the following University of Florida paper:

http://edis.ifas.ufl.edu/AG224

The purpose here is not to identify which plants can grow in conditions similar to space, but to identify which genes allow any plant to grow in conditions similar to space. Those genes might then be recombined with alternative plant DNA to grow other varieties in the same conditions.