Shu Funada

Identification of Water Deficiency and Photosynthesis in Short-Term Plant Growth Under Random Variation of the Environment

Abstract Recent advances in environmental control in protected cultivation (modern agriculture) have been remarkable. Identification of water deficiency and photosynthesis is essential for the optimal control of plant growth. In the present report, identification of water deficiency and photosynthesis is examined by monitoring the leaf temperature and water content in the stem in a computer controlled growth chamber as well as by analog simulation of a mathematical model. The responses of leaf temperature and water content in the stem caused by environmental inputs of a random binary signal are examined by spectral analysis. The method is found to be effective in the identification of plant growth.

Optimal Control of Greenhouse Climate by the Identification of Water Deficency and Photosynthesis in Short-term Plant Growth

Abstract The optimal control of plant growth was examined separately for the transient state from sunrise to mid-day and for the steady state in mid-day. To prevent strong water stress during the transient state, a computer controlled system of monitoring leaf temperature was designed using a humidifier. On the other hand, in the steady state, photosynthesis was found to be greater when plants were appropriately water stressed. Based on these findings, a computer controlled system was also designed where a 1.9-fold increase in dry matter was attained during a 2-week cultivation period over that of the control system commonly used.