Studies on Improvement of Tomato Productivity in a Large-scale Greenhouse

Abstract

We have been conducting research on the improvement of productivity in largescale greenhouse tomato production. One of the factors that largely influence the tomato productivity is the rate of CO 2 fixation by photosynthesis. The amount of CO 2 fixed by the whole plant canopy varies considerably and is known to depend on canopy structure. To date, few studies have analyzed photosynthesis in plant canopies within the context of improving productivity for largescale tomato production. Consequently, obtaining data and developing analytical methods that are relevant to production is important. The present study investigated the rate of photosynthesis within a plant canopy and the vertical distribution of the amount of CO 2 fixed by plants with the aim of increasing CO 2 fixation and yield. This was done by analyzing the photosynthetic rate in individual leaves, examining plant canopy structure and measuring light intensity within the plant canopy. It was found that the leaves located in the upper parts of canopies were exposed to higher light intensities, experiencing light saturation and had higher rates of photosynthesis at the point of light saturation than leaves in the middle and lower parts of the plant. It was assumed that this was due to the occurrence of senescence and the development of shadeleaf characteristics in the leaves of the lower parts of the plant. The results implied that removal of the leaves under 150 cm or farther from the apical meristems could increase CO 2 fixation and productivity of the plant canopy. The analytical methods developed in the present study can be applied to assess the efficacy of seasonal management methods such as cropping patterns, utilization of lateral buds, and leaf thinning, for maximizing yields.