Influence of Nitrate on Tomato Growth1,2

Abstract

Abstract Tomato plants (Lycopersicon esculentum L. cv. VF 145-21-4) in the greenhouse developed over a 5-week period from seedling to early bloom stage, increased in fresh and dry weight of shoots and roots, in plant height, and internal NO3-N concentration in relation to the NO3 supply of the culture solution. Increases in NO3-N varied among plant parts: roots < stem < petiole > blade. Growth of shoots was related to NO3-N concentration in plant parts. A petiole from a young mature leaf, leaf 2, was the best indicator of N status of the plant. Its critical value for N deficiency was 275 ppm of NO3-N (dry wt) when estimated at a 10% reduction in growth. A tentative critical value for use under field conditions was set at 500 ppm. Movement of NO3 was primarily unidirectional from the petiole to the blade, with little return movement to the stem and upward to younger petioles.