The Effects of Leaf Position and Time of Sampling on Nutrient Concentration in the Petiole Sap from Tomato Plants Cultured Hydroponically.

Tomato plants (Lycopersicon esculentum Mill. cv. Momotaro) were cultured hydroponically. The effects, under different weather conditions, of leaf position and sampling time of day on the concentration of nutrient elements in the petiole sap from leaves under the fruit truss at two growth stages were investigated. At the flowering stage of the second truss, the NO3-N, P, and K concentrations in the petiole sap did not differ among the three leaves under the first truss. At the fruit growth stage of the second truss, no difference in the P and K concentrations existed among the three leaves under the second truss. The concentration of NO3-N in the petiole sap collected from the leaf just below the second truss, however, was clearly lower than those of the other two adjacent leaves. At both growth stages, the higher the leaf position among the three leaves under the fruit truss, the lower were the Ca and Mg concentrations in the petiole sap. Variations in the concentrations of nutrient elements in the petiole sap were minimal at different times of day and under differing weather conditions.