Ion uptake and structural modifications induced by nitrogen source in tomato (Solanum lycopersicum Mill. Cv. Ibiza F1).

Interactions between NO(3)(-) and NO(2)(-) were studied at the level of root uptake, ion translocation (NO(3)(-), NO(2)(-), K(+)), ion xylem exudates composition and inorganic cation contents (K(+), Ca(2+), Mg(2+)) using tomato seedling (Solanum lycopersicum Mill cv. Ibiza F1). Nitrite was supplied in the medium as KNO(2) (0, 0.25, 2.5, 5 and 10 mM). Plants cultivated on the same doses of KNO(3) served as control. The experimental system allowed direct measurements of net NO(3)(-) and NO(2)(-) uptake. Our results showed that NO(3)(-) uptake and translocation were stimulated by external supply of K(+), while they were hardly decreased by NO(2)(-) supply. Contents of K(+) and Mg(2+) were negatively affected in all tomato tissues by increasing nitrite concentration in the medium. Highest dose of NO(2)(-) decreased Ca(2+) accumulation in shoots and conversely increased that in the roots. Histological study at the stem level revealed that nitrite (10 mM) induced a restriction of the tissue territories as well as less developed regions and some conductor tissues disorganization in this organ structure. The overall results suggest that nitrite exposure delayed growth and injured cell structure and overall nutrient uptake.

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