Trickle water and feeding system in plant culture and light-dark cycle effects on plant growth.

Rockwool, as an inert medium covered or bagged with polyethylene film, can be effectively used for plant culture in space station. The most important machine is the pump adjusting the dripping rate in the feeding system. Hydro-aeroponics may be adaptable to a space laboratory. The shortening of the light-dark cycles inhibits plant growth and induces an abnormal morphogenesis. A photoperiod of 12-hr-dark may be needed for plant growth.     

Thermal and nonthermal flare emission observed with the Nobeyama Radio Heliograph

The early phases of three flares, observed by the Nobeyama Radio Heliograph, are studied. Nonthermal and thermal radio sources are identified by comparison with soft X-ray images taken by the Soft X-ray Telescope onboard the Yohkoh satellite. Two of the flares are mainly of nonthermal origin and their location coincides with one of the footpoints of soft X-ray loops. Another flare has both thermal and nonthermal components which start to brighten simultaneously. This suggests that particle acceleration and plasma compression develop simultaneously.     

Planetary protection on international waters: An onboard protocol for capsule retrieval and biosafety control in sample return mission

Planetary protection has been recognized as one of the most important issues in sample return missions that may host certain living forms and biotic signatures in a returned sample. This paper proposes an initiative of sample capsule retrieval and onboard biosafety protocol in international waters for future biological and organic constituent missions to bring samples from possible habitable bodies in the solar system. We suggest the advantages of international waters being outside of national jurisdiction and active regions of human and traffic affairs on the condition that we accept the Outer Space Treaty. The scheme of onboard biological quarantine definitely reduces the potential risk of back-contamination of extraterrestrial materials to the Earth.     

Agravitropic mutant for the study of hydrotropism in seedling roots

Roots have been shown to respond to a moisture gradient by positive hydrotropism. Agravitropic mutant plants are useful for the study of the hydrotropism in roots because on Earth hydrotropism is obviously altered by the gravity response in the roots of normally gravitropic plants. The roots are able to sense water potential gradient as small as 0.5 MPa mm⁻¹. The root cap includes the sensing apparatus that causes a differential growth at the elongation region of roots. A gradient in apoplastic calcium and calcium influx through plasmamembrane in the root cap is somehow involved in the signal transduction mechanism in hydrotropism, which may cause a differential change in cell wall extensibility at the elongation region. We have isolated an endoxy loglucan transferase (EXGT) gene that is strongly expressed in pea roots and appears to be involved in the differential growth in hydrotropically responding roots. Thus, it is now possible to study hydrotropism in roots by comparing with or separate from gravitropism. These results also imply that microgravity conditions in space are useful for the study of hydrotropism and its interaction with gravitropism.     

Basic investigations on an angle measurement system using a laser

A novel, precise angle gauge is proposed. Incoming laser light is fed to the system through two separate condensing lenses. The phase difference between two rays is compensated by a phase modulator to hold a constant interference condition. The angle of the incoming light is measured by the modulation voltage. In comparison with conventional angle gauges, its advantages are high measurement accuracy, simple structure, and compatibility to feedback control systems. Because of these advantages, the angle gauge is suitable for navigation using angular information. Some examples of possible applications are provided. The experimental system was formed to be compatible with practical conditions and performance were verified experimentally. It is shown that an angle resolution less than 1×10^-7 rd can be expected