Variation in Diurnal Uptake of Water and Nutrients by Tomato Plants of Different Growth Stages Grown in Water Culture

Abstract

Water and nutrient (N03-N, P04-P, K, Ca and Mg) uptake by tomato (Lycopersicon esculen-tum Mill. cv. Ohgata-Fukuju) plants during the day (7:00 to 19:00) and night (19:00 to 7:00) was measured. Measurements were made for 4 days on each plant at 3 developmental phases: a) 8-leaf seedling, b) the first truss was flowering, and c) when fruits were growing. URN (ratio of the uptake rate during the night to that of the 24-hr day, expressed in percentage) of phosphate was highest as compared to those of water and nutrients at all plant growth stages. URN of nutrient was highest when the first truss was flowering and lowest when the fruits were growing. URN of phosphate was relatively high as compared to that of water at the fruit growing stage. These results show that URN of nutrients changes depending on the growth stage of tomato plants and may reflect the nutritional status and possibly the demand for certain nutrients by tomato plants grown hydroponically.