It is of crucial importance to know the influence of varying gravity levels on plant growth. The life of plants is dependent on the gravity of 1-G on earth. The Spacetron Junior (SJ) designed for this preliminary experiment was used to create simulated microgravity and hypergravity conditions by controlling the centrifugal force.
An experiment was designed to study the influence of clinostat rotation rate on plant growth. Gravity is a fixed factor for a definite earth position and is used as a standard of comparison. A gravity level of 10^-2-G was selected for this study. The plants were placed at 32.25 and 30 cm from the centrifuge axis and they were rotated about the clinostat axis at 5.2 and 10 rpm, respectively, to cancel the physiological effect of 1-G earth gravity on the plant. The corresponding centrifuge rotations were 5.2 and 5.4 rpm. The plants under microgravity condition were smaller as compared to those under control when the clinostat rate was 5.2 rpm. All parameters such as leaf area, fresh weight are higher of test plants at rotation of 10 rpm than the control plants except plant height. The results show that an increase in the rate of clinostat rotation causes an increase in plant growth. During these experiments the SJ was run for a period of two month continuously without interruption and found the overall performance of the SJ was satisfactory.

View full abstract

A measurement system, which measured gross photosynthesis and respiration of the plant discriminately and simultaneously, was developed. The measurement was carried out by controlling ¹³CO₂ and ¹²CO₂ concentration of plant's ambient gas adequately. To formulate the equations of gross photosynthetic CO₂ absorption rate (V_PCO2) and respiratory CO₂ evolution rate (V_RCO2) two assumptions were made. One is that the evolution of the ¹³CO₂ absorbed by photosynthesis is negligible during the measurement. Another is that ¹²CO₂ and ¹³CO₂ are absorbed at the same rate by photosynthesis. In order to verify the measurement system, V_PCO2 and V_RCO2 of komatsuna leaf were measured by semi-closed circulation method and open method. In this paper, the formulation method and the measurement system is shown. And it is considered that the application of the measurement method to the material circulation analysis in CELSS.

View full abstract