Organic farming promotes selective uptake of glycine over nitrate uptake by pakchoi

ABSTRACT

Understanding how plants use of various nitrogen (N) sources is important for improving plant N use efficiency in organic farming systems. This study investigated the effects of farming management practices (organic and conventional) on pakchoi short-term uptake of glycine (Gly), nitrate (NO₃⁻) and ammonium (NH₄⁺) under two N level conditions. Results showed that plant N uptake rates and N contributions from the three N forms in the low N (0.15 μg N g⁻¹ dry soil) treatment did not significantly differ between the organic and conventional soils, except the significantly greater Gly contribution in organic soil at 24 h after tracer addition. Under high N (15 μg N g⁻¹ dry soil) conditions, the N uptake rates, uptake efficiencies, and N contributions of Gly and NH₄⁺-N were significantly greater in pakchoi cultivated in the organic soil compared to conventional soil, whereas the N uptake rates and N contributions from NO₃^–-N decreased in pakchoi cultivated in the organic soil. The greater Gly-N uptake in plants grown in high-N treated organic soil may be related to the greater gross N transformation, Gly turnover rate and the increased expression of an amino acid transporter gene BcLHT1. Intact Gly contributed at most 6% to Gly-derived N at 24 h after tracer additions, which accounting for about 1.24% of the total N uptake in organic soil. Our study suggested that Gly-N and other organic source N might serve as a more important compensatory N source for plants in organic farming.

KEY WORDS:

• Gene expression
• isotope
• organic farming
• organic nitrogen
• uptake

Disclosure statement

No potential conflict of interest was reporter by the authors.

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Additional information

Funding

This work was supported by the Natural Science Foundation of Shanghai (No. 15ZR1431300), National Natural Science Foundation of China (No. 31601744) and Shanghai Engineering Research Center of Plant Germplasm Resources (No. 17DZ2252700).