Abstract
A system for non-destructive and continuous measurement of fresh weight was developed consisting loadcell and hydroponics. The readings of the system were not affected by temperature fluctuation, and the hysteresis was little. The readings were in good agreement with the fresh weight of leaf bunching lettuce above the surface of the hydroponic solution, and almost the same as the top fresh weight, when the solution level was high.
Using this system, daily change of top fresh weight was monitored and daily growth rate was calculated. The weight increased from 4.4 g to 102.6 g in 17 days. The growth rate and the transpiration rate were the lowest, when the weight was about 10 g. The growth rate was the highest and the leaf area index was almost optimum, when the weight was about 30 g.
It was concluded that this system can monitor the change of the top fresh weight continuously.
