Carbohydrate and free amino acid contents in tomato plants grown in media with bicarbonate and nitrate or ammonium

Tomato plants were cultivated (from 2 to 23 days after germination) in media with NO3-, NH4+, or a mixture of both forms in different proportions used as the N source given with or without 5 mol dm(-3) HCO3-. The accumulation of soluble sugars (reducing sugars and sucrose) and free amino acids was higher in the roots and leaves of NH4+-fed plants than in NO3--fed plants. Starch accumulation in NH4+-fed plants was higher in leaves (about 28 %) and lower in roots (about 37 %) in comparison with that of NO3-- fed plants. Plants cultivated in media containing a mixture of NO3-/NH4+ were characterized by a lower content of sugars and amino acids accumulation in comparison with that in plants fed with NO3- or NH4+. An elevated HCO3- concentration in the rhizosphere stimulated the accumulation of soluble sugars and free amino acids in all the experimental variants. There were only small differences in the starch content.