• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.50-58
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• 1995

These studies were carried out to develop a system for non -destructive and continuous measurement of fresh weight and to analyse the growth response of leaf lettuce under the different nutrient solution and light condition with this system. The developed measurement system was consisted of four load cells and a microcomputer. The output from the system was highly positive correlation with the plant fresh weight above the surface of the hydroponic solution. The top fresh weight of plant could be measured within the error $\pm$ 1.0g in the range of 0 - 2000g. The top fresh weight of leaf lettuce increased 44 times at 18th day after transferring to the nutrient solution, and the maximum growth rate was observed at 13th day after transferring. The growth rate was 10.7- 29.6% per day during 18 days. Optimum concentration of the nutrient solution for the growth of lettuce was 1.4 - 2.2 mS/cm of EC level. When the light condition was changed from dark to light, the fresh weight was temporarily decreased, but the fresh weight increased under the opposite condition. Top fresh weight of leaf lettuce in the darkness normally increased within 12 hours after darkness treatment, and then slowly increased until 78 hours under continuous dark condition. After that times, the fresh weight began to decrease.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.63-70
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• 1998

This study was carried out to investigate the interaction of selenate and sulfate ion in nutrient solution supplyed with selenate ion. At early growth stage, the growth of Mongolian wormwood was best at 3mM sulfate ion and 2mg/$\ell$Na$_2$SeO$_4$ treatment. As they were grown and matured, at the later growth stage, the effect of antagonism between selenate and sulfate ion on the growth of each plant decreased. At supplying with selenate ion in nutrient solution, the uptake of selenate by plant had negative correlation with sulfate ion concentration in nutrient solution. The higher sulfate ion concentration, the less selenium uptake. However, the effect of antagonistic interaction of selenate and sulfate ion on the selenium uptake increased with plant age. Whereas, the uptake of sulfate ion had positive correlation with sulfate ion concentration in nutrient solution at supplying with selenate ion in nutrient solution. The uptake of sulfate ion increased with increase of sulfate ion concentration in nutrient solution. The effect of this interaction with selenate and sulfate ion increased with growth and maturity of plant. However, at 3mM sulfate ion concentration in nutrient solution, sulfate ion concentration in plant tissue decreased markedly.