Design of an acclimation system capable of controlling carbon dioxide concentration.

The production system for grafted seedlings mainly consists of three processes; 1) growth of seedlings, 2) grafting of seedlings, and 3) acclimation of grafted seedlings. Of the three processes, the duration of acclimation is highly influenced by the acclimation conditions. The acclimation environment after grafting was controlled to be satisfied the demands of grafted seedlings in the point of the physiological reaction such as photosynthesis, respiration, transpiration, and translocation nutrients. In the present study, a preliminary experiment was conducted to understand the relationship between the factors concerned with the acclimation of grafted seedlings, using a new acclimation apparatus. The factors of interest were air temperature, relative humidity, light, and carbon dioxide concentration. In the presence of light, the air temperature and relative humidity were interfered each other, so that both factors were difficult to keep at a constant value. Furthermore, the concentration of carbon dioxide was remarkably fluctuated by the relative humidity regulated by the humidifier and dehumidification which was controlled by the temperature differences between water and ambient air. A new device of acclimation system which is automatically controlled would be expected to construct in near future. Such a device will make it possible to shorten the duration of acclimation and produce high quality of grafted seedlings.

Development of centrifugal phytotron to study the gravity effect on vegetable plant growth.

The present Spacetron is used to cultivate plants over a long term by controlling environment condition. The cultivation drum was rotated in perpendicular direction creating fluctuation in gravity. Centrifugal force plus 1 G ground gravity, are distributed unevenly over the cultivation drum. This fluctuation effect on plant growth was not clear. In the modified Spacetron the cultivation drum rotates horizontally whereas the plant stage rotated in the perpendicular direction. To find the basic information for design of centrifugal phytotron the two axes Spacetron Junior (clinostat) was developed to formulate the micro and hypergravity environment. It would be used to study the effect on a plant growth process of different gravity conditions. In order to produce the different values of gravity, the clinostat's axis was rotated with a stepping motor at different angular velocity. The axis rotated at 5.2 revolutions per minute (rpm) to create a centrifugal force equivalent to 0.01 G and the plant stage was rotated at 5.2 rpm. The chlorophyll value is higher in the plants under microgravity condition of 0.01 G whereas the fresh weight and dry weight are higher in the plants under control condition of 1 G earth gravity. The result of this study showed that the plant growth was affected by microgravity along with other known factors such as vibration and unknown factors.

Performance of a centrifugal phytotron.

It is possible to cultivate plants under an artificial gravity field generated by a centrifugal device in space. In order to determine an optimal magnitude of gravity, there is a need to investigate the relationship between plant and growth and gravity, including not only reduced gravity but also gravity greater than 1G. A prototype centrifugal phytotron was designed and fabricated in order to investigate the relationship between plant growth and increased gravity. This device enables us to cultivate plants over the long term by controlling environmental conditions in the phytotron such as temperature, relative humidity, CO2 concentration and light intensity. The results of our experiment indicate that plant seeds can germinate and grow even under an artificial gravity which changes sinusoidally from 2G to 4G.