Abstract
Effects of environmental factors (Experiment I) and NPK fertilizers (Experiment II) on leaf water potential of tomato (Lycopersicon esculentum Mill. cv. Momotaro) plants potted in 3 soil types: yellow, kuroboku, and sand were studied. In Exp. I, potted tomato plants were grown in a glasshouse and then transferred to a growth chamber. The environmental factors were: air and soil temperatures, relative humidity, light intensity, wind velocity, and soil moisture content. In Exp. II, the entire experiment was conducted in the glasshouse using similar materials; the experimental variable was the amount of NPK fertilizer applied. The results are:
1. A rise in light intensity, air temperature and wind velocity caused a decrease in leaf water potential (ψl), whereas a rise in relative humidity increased ψl.
2. An increase in soil water suction and in the amount of fertilizer applied resulted in a decrease in ψl, whereas a rise in soil temperature increased ψl. It is concluded from these results that ψl decreased under environmental conditions which promote transpiration and/or suppress water uptake by roots.
