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.