Adhesion, germination and hyphae elongation of/from spores of Aspergillus tonophilus on a silica aerogel were observed, to indicate the possibility of mold contamination of the material designed for astrobiology mission using Kibo module in ISS. Spore germination seemed to be encouraged by nose sebum treatment before adhesion. Spore adhesion was observed by electron microscopy, and autofluorescence from mycelia was observed both by conventional microscope and USB-probe type microscope. The use of latter device was indicated to be effective for the monitoring of possible mold contamination of aerogel samples returned to earth in the astrobiology mission.
Tuber formation in potato (Solanum tuberosum L.) under hypergravity conditions in a centrifuge and simulated microgravity (μG) conditions on a horizontal clinostat was studied using in vitro culture of single-nodal stem segments prepared from sprouting tuber shoots. Hypergravity conditions at 100 G for 6 days reduced the growth of axillary bud (or stolon) of a single-nodal stem segment; the length, diameter, and fresh weight of the stolon developed under hypergravity conditions were 53%, 66%, and 74% of 1 G control, respectively. Promotion of swelling seen in the shoot under hypergravity conditions was not observed in the stolon. The size of cells and starch grains in the epidermal tissues in the swelling stolon were reduced under hypergravity conditions. On the other hand, the length of the stolon and the size of the tuber developed in the single-nodal stem segment under simulated μG conditions on a horizontal clinostat for 3 weeks were significantly increased as compared with the 1 G control. These results suggest that stolon growth and tuber formation in the single-nodal stem segment are under the control of gravity. Further studies on the molecular mechanism how gravity regulates tuber development and starch synthesis will be required for increasing potato tuber production in space.
