DISTRIBUTIONS OF STEM DIAMETER AND STEM ELONGATION RATE IN A LARGE-SCALE TOMATO PRODUCTION GREENHOUSE - MEASUREMENT OF THOUSAND PLANTS

The Speaking Plant Approach (SPA) is regarded as a desirable and indispen-sable concept for environmental control in highly sophisticated greenhouses. The SPA is based on the paradigm that the optimization of crop cultivation conditions should be based on measurements of the plant physiological status. The weekly monitoring of stem diameter and stem elongation rate is the most traditional and fundamental SPA in year-round tomato production. In general, the stem diameter and stem elongation rate of the specified 6-10 plants selected from 25,000-75,000 plants grown in 1-2 ha cultivation area are measured. Based on these values, growers judge whether or not the plant’s growth is balanced. However, the distributions of stem diameter and stem elongation rate in a commercial large-scale greenhouse have never discussed. In this study, the stem diameter and stem elongation rate of more than 1,000 tomato plants selected from 30,000 plants in a 1.3 ha cultivation area were measured and the distribution of these parameters across the cultivation area was investigated. The maps of stem diameter and stem elongation rate revealed that the plant with a thick stem showed a shorter stem elongation. Furthermore, an additional investigation of night air temperature distribution demonstrated that the plants with thicker and shorter stems were located in the lower air temperature areas.