S08 - Session P7 - Long-term continuous measurement of photosynthetic and transpiration rates, and material and energy balances of edible crops in a closed cultivation system designed for a lunar-base plant factory

Authors: Eiji Goto *, Hideo Yoshida, Shoko Hikosaka

In this study, we aimed to collect basic data for crop production and resource recycling in a lunar-base plant factory for the development of a food supply system to support long-term stay of human beings on the Moon. We developed a closed-type cultivation system equipped with a growth shelf to evaluate photosynthesis, respiration, transpiration, and nutrient ion absorption by plants and electric energy consumption for the operation. The system consists of a high air-tight growth shelf, an air conditioning unit, an air current control device, LED lamps, a hydroponic container, a remote camera, and an environment and plant data acquisition subsystem. The growth shelf can be used to grow eight candidate food crops, namely rice, soybean, potato, sweet potato, tomato, strawberry, cucumber, and lettuce. It has the advantage of high space-utilization efficacy. The shelf measures 260 cm (width) and 60 cm (depth). Types A and B measure 60 cm in height for tall crops and 120 cm for short crops, respectively. We prepared 8 Type A systems and 4 Type B systems. The air current device controls the flow speed of air surrounding a plant canopy, in the range of 0.3n1.0 m s -1 , and LED lamps provides a maximum PPFD of 800 µmol m -2 s -1 at a growth panel. The camera analyzes leaf area, number of leaves, and LAI of plants. The data acquisition subsystem measures CO 2 and H 2 O concentrations at the inlet and outlet of the shelf continuously and calculates photosynthetic, respiration, and transpiration rates of plant canopy at 5-min intervals; it also calculates energy consumption. Ion absorption by plants is estimated using an off-line ion chromatography analysis. The operation test showed that the system can be used to cultivate plants from the seedling to harvest stages with high space-utilization efficacy and obtain long-term continuous measurement of plants.