Potassium and Nitrogen Distribution Pattern and Growth of Flue-Cured Tobacco Seedlings Influenced by Nitrogen Form and Calcium Carbonate in Hydroponic Culture

ABSTRACT

The influences of nitrogen form (NH₄ ⁺, NO₃ ⁻, and NH₄NO₃) with or without CaCO₃ on the growth and potassium (K) and nitrogen (N) uptake and partitioning of flue-cured tobacco plants (Nicotiana tabacum L. cv. ‘K326’) were examined under the controlled conditions of nutrient-solution culture. Tobacco seedlings with four true leaves were grown in mixed substrate before being transplanted and grown in a pre-culture solution until the six-true-leaf stage. The following treatments were applied: NH₄ ⁺-, NO₃ ⁻-, and NH₄NO₃ alone, and each of these in combination with CaCO₃. Seventeen days later, the plants were harvested. The results showed that NH₄ ⁺ as the only N source resulted in lower dry weight of both leaves and roots compared with other N forms, including NO₃ ⁻ and NH₄NO₃, without obvious ammonia toxicity in leaves. The CaCO₃ addition was beneficial in ameliorating the growth suppression found in NH₄ ⁺-only plants, but the same effects of addition were not found in NO₃ ⁻-only plants. Sole NH₄ ⁺ nutrition led to the lowest K concentration and content in leaves and roots, while sole NO₃ ⁻-only plants had the highest. Added CaCO₃ also significantly improved the K concentration and content in NH₄ ⁺-only plants. However, NH₄ ⁺ nutrition resulted in more K translocated to leaves than did NO₃ ⁻ supply. Nitrogen concentration and content were only weakly affected by N form. Although NH₄ ⁺-only plants had the lowest N concentration and content in plants, there was no difference in N concentration in top leaves and roots between NH₄ ⁺ and NO₃ ⁻-plants. Added CaCO₃ also improved the N concentration in NH₄ ⁺-only plants. In contrast to its effect on K partitioning, the NH₄ ⁺-only treatment the lowest N concentration in leaves, while no differences in N partitioning were observed under other treatments. These results suggest that long-term use of 100% NH₄ ⁺ in the nutrient solution reduces dry-matter accumulation and K uptake in tobacco plants and increases K accumulation in leaves. Added CaCO₃ could reduced the suppression induced by 100% NH₄ ⁺ to a certain extent.

Keywords:

• calcium carbonate
• flue-cured tobacco plants
• nitrogen form
• nitrogen partitioning
• potassium partitioning

ACKNOWLEDGMENTS

We thank the Institute of Tobacco Science in Yunnan province for providing tobacco seedlings. This study was supported financially by the National Natural Scientific Foundation of China (Grant No. 30000103).