2020 年 32 巻 2 号 p. 15-21
The Speaking Plant Approach (SPA) is regarded as a desirable concept which defines that the environmental factors should be adjusted to the crop’s physiological status. The first and most important step in the SPA concept is to obtain physiological information from a living plant. Especially for environmental control in highly sophisticated greenhouse, daily measurement of plant growth must be indispensable in SPA concept. In our previous study, a robotized chlorophyll fluorescence (CF) imaging system that evaluates daily changes in photosynthetic function of tomato canopy has been developed and came onto the market in 2015. In this study, we applied the robotized CF imaging system to measure the daily stem elongation of tomato plants grown in greenhouse. CF images of shoot apex of tomato plants were taken by using the robotized CF imaging system and detected the shoot apex manually by using commercially available image analysis software to obtain the average plant height. Then, the daily stem elongation was calculated by subtracting the average plant height of one day before from that of the day. The performance verification test proved that the spatial resolution of CF image was 1.6 mm pixel-1 and the reproducibility of average height measurement was within 0.01 %. And, a long-term stem elongation monitoring for consecutive 70 days, which was done with the conventional weekly stem elongation monitoring by using a measuring tape, suggested that daily stem elongation is able to be monitored with the robotized CF imaging system.