Zinc Accumulation in Indian Mustard as Influenced by Nitrogen and Phosphorus Nutrition

Abstract

Mineral nutrition influences plant growth and absorption of elements, which are two factors that influence the accumulation of elements in plant tissues. Proper nutrition may enhance zinc (Zn) accumulation in plants and their potential for land remediation by phytoextraction. Objectives of this study were to determine the effects of nitrogen (N) and phosphorus (P) supply on growth and Zn accumulation by Indian mustard (Brassica juncea Czern.) under simulated Zn‐contaminated conditions. In a factorial experiment, B. juncea (accession 426308) was supplied with five levels of N (50, 150, 250, 350, and 450 mg L⁻¹) in combination with four levels of P (5, 20, 35, and 50 mg L⁻¹) for 3 weeks in solution culture. All solutions contained 3.0 mg Zn L⁻¹, a level of Zn determined to cause Zn toxicity in B. juncea. Although plants had a mean leaf Zn concentration of 639 µg g⁻¹, they did not exhibit symptoms of Zn toxicity (chlorosis of young leaves). Shoot dry mass increased from 9.6 to 14.0 g plant⁻¹ with increasing supply of N up to 150 mg N L⁻¹, but higher levels of N supply did not increase shoot mass further. Plant growth was not influenced by the supply of P in solutions. Mean shoot Zn concentration increased from 483 to 680 µg g⁻¹ as the N concentration in solution increased from 50 to 350 mg N L⁻¹, and shoot Zn concentration increased from 580 to 674 µg g⁻¹ as the P supply in solution increased from 5 to 50 mg L⁻¹. Total Zn accumulation (mg plant⁻¹) in B. juncea shoots increased by 100% (from 4.6 to 9.3 mg Zn plant⁻¹) as the supply of N increased from 50 to 350 mg L⁻¹ and by 20% (from 7.3 to 8.8 mg Zn plant⁻¹) as the supply of P increased from 5 to 50 mg L⁻¹. Iron concentrations in B. juncea roots increased, and concentrations in leaves decreased with increasing supply of P, indicating that plants may be more prone to Fe deficiency with increased P fertility. Results suggest that N fertility, and to a lesser extent P fertility, can be used to increase the Zn phytoextraction potential of B. juncea.

Keywords:

• Brassica juncea
• Heavy metals
• Phytoextraction
• Phyto‐remediation

Acknowledgments

The authors thank the USDA North Central Region Plant Introduction Station at Iowa State University for their generous donation of B. juncea seeds. This report is based on research supported by the Cooperative State Research, Extension, Education Service, U.S. Department of Agriculture, Massachusetts Agricultural Experiment Station, under Projects 756 and 841. Paper no. 3318 in the journal series.