S08 - Session P7 - An alternative method for growth analysis of lettuce grown in a plant factory with artificial lighting using projected canopy area and fresh mass

Authors: Masatake Eguchi *, Ayumi Enjoji, Junichi Yamaguchi, Yasunaga Iwasaki, Yoshiaki Kitaya

The relative growth rate (RGR), the net assimilation rate (NAR), and the leaf area ratio (LAR) are parameters for plant growth analysis. Since RGR is the product of NAR and LAR, it can be determined whether the reason for the low RGR is due to the low photosynthetic capacity per unit leaf area indicated by NAR or due to the suppression of the leaf area expansion indicated by LAR. Therefore, growth analysis is useful for efficient environmental control. In this study, leaf area, which is a parameter used to determine NAR and LAR, was replaced with projected canopy area measured with Kinect sensor, and dry mass, which is a parameter used to determine RGR, NAR, and LAR, was replaced with fresh mass to analyze plant growth non-destructively. The dry mass, the fresh mass, the leaf area, and the projected canopy area of leafy lettuce ( Lactuca sativa L. var. crispa 'Green jacket') plants grown in the plant factory with artificial lighting at Osaka Prefecture University (Sakai City, Osaka, Japan) were monitored for two weeks after planting. The results showed that the correlation coefficient (r) between NAR and NAR' determined with projected canopy area and dry mass was 0.957, and that between LAR and LAR' determined with projected canopy area and dry mass was 0.964. Furthermore, the r values between RGR and RGR″ determined with fresh mass, between NAR and NAR″ determined with projected canopy area and fresh mass, and between LAR and LAR″ determined with projected canopy area and fresh mass were 0.998, 0.964, and 0.945, respectively. These results suggest that plant growth analysis can be performed non-destructively by using measurements of the projected canopy area and fresh mass.