Variation in the use efficiency of N under moderate water deficit in tomato plants (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis>) differing in their tolerance to drought

Nitrogen-use efficiency (NUE) is one of the determining factors in crop productivity. However, the accumulation and use of this nutrient can be affected by several elements, including the species or cultivar and the water supply. Currently, one agricultural priority is to improve NUE together with greater water-deficit tolerance of crops in Mediterranean environments in order to reduce the application of nitrogenous fertilizers and boost production. The aim of the present study was to evaluate the response of different tomato-plant genotypes in relation to NUE under water stress conditions and optimal nitrogen condition. The water deficit provoked a decline in the concentration and uptake of N in all the cultivars except in cv. Zarina, which improved its NUE under these conditions. In turn, it was this cultivar which underwent the strongest relative growth during water stress together with the greatest leaf relative-water content, which could be associated with improved NUE.