Takakazu Namiki

Effect of restricted supply of nitrate on fruit growth and nutrient concentrations in the petiole sap of tomato cultured hydroponically

Abstract Tomato plants (Lycopersicon esculentum Mill. cv. Momotaro) were cultured in nutrient solution supplying 35 meq or 50 meq of nitrate (NO3) per plant weekly from the flowering stage of the first truss in two cropping seasons. The effects of NO3 supply levels and cropping season on fruit growth of tomato were investigated. Furthermore, the relationship between the results of the plant sap analysis and fruit growth of tomato was analyzed. In the spring to summer cropping, NO3 supplied was almost all absorbed and high productivity of tomato fruits was obtained in each treatment. In the fall to winter cropping, however, high NO3 supply did not increase the uptake of NO3, but tended to decrease the rate of fruit set and marketable yield. Accumulation of NO3 in the petiole sap was found with high NO3 supply in the fall to winter cropping. Cropping season greatly influenced not only fruit growth but also the concentration of NO3 in the petiole sap in relation to the ability of tomato plants to use availab...

Comparison between analytical results of plant sap analysis and the dry ashing method for tomato plants cultured hydroponically

Abstract Tomato plants (Lycopersicon. esculentum Mill cv. Momotaro) were cultured in nutrient solutions of varying concentrations or of varying nitrate (NO3) levels. The leaf blades and the main petioles including rachis were collected from the mixture of three successive leaves below each fruit truss at two growth stages. Comparisons were made between the nutrient concentration in the leaf blade and the petiole determined by plant sap analysis, and that in the leaf blade determined by the dry ashing method. Closely correlated relationships were found to exist between the phosphorus (P), calcium (Ca), and magnesium (Mg) concentrations in the leaf blade and the petiole determined by plant sap analysis, and those in the leaf blade determined by the dry ashing method at two growth stages. For the concentration of potassium (K), there was no correlation between results of plant sap analysis and those determined by the dry ashing method at either growth stage.