Influence of Nitrogen on Physiological Responses to Bicarbonate in a Grapevine Rootstock

Abstract

The presence of bicarbonate in soils is an important inducer of nutritional deficiencies in some grapevine genotypes. The aim of this experiment was to assess the effects of different nitrogen sources on physiological variables in the grapevine rootstock 110 Richter grown in a sub-alkaline media. Plants of the grapevine rootstock 110 Richter were treated with different nitrogen sources (NO3−, NH4+, or NH4NO3) in a nutrient solution enriched with bicarbonate. Root enzyme (PEPC, MDH, CS, NADP+-IDH) activities, organic acid concentrations in roots, plant growth and leaf greenness, leaf gas exchange, and mineral concentrations in leaves were determined. The presence of NH4+ promoted an enhancement in leaf greenness, and the treated plants did not trigger physiological response mechanisms to nutritional deficiencies in the roots. However, NH4+ decreased the leaf K concentration. On the other hand, the presence of NO3− in the nutrient solution decreased the leaf greenness, and increased the organic acid concentration in the roots, indicating that these plants were affected by nutritional deficiencies. Instead, intermediate results were obtained in plants treated with NH4NO3. Under the experimental conditions used in this experiment, treatments did not significantly influence the plant biomass, the activity of some enzymes related to organic acids biosynthesis, and the leaf gas exchange. These results suggest that the presence of NH4+ can be an effective strategy to alleviate the negative effects on plant nutrition induced by bicarbonate in plants, an alternative to the soil acidification through inorganic acid applications to the soil.