Different nitrogen forms differentially affect Cd uptake and accumulation in dwarf Polish wheat (Triticum polonicum L.) seedlings

This study investigated the effects of different nitrogen (N) forms on Cadmium (Cd) uptake and accumulation in dwarf Polish wheat (DPW) seedlings, which were grown under Cd stress with N-Null, NH4+-N, NO3-N and NH4+-N + NO3-N. We measured plant growth and determined Cd uptake, translocation, accumulation, subcellular distribution and chemical forms in the roots and shoots of DPW seedlings. We also analyzed saccharide concentrations, and the transcript levels of genes encoding metal transporters in the roots of DPW seedlings. In the absence of NO3-N, addition of NH4+-N reduced roots Cd concentration, FCW (Cd in cell wall), FS (Cd in soluble fraction) and FE (inorganic Cd) concentrations, and induced the expression of four genes encoding metal transporters in roots, while it promoted Cd translocation to shoots. In the presence of NO3-N, addition of NH4+-N increased roots Cd concentration, FCW and FW concentrations, and induced the expression of 22 genes encoding metal transporters in roots. Regardless of NH4+-N level, addition of NO3-N increased roots Cd concentration, FCW, FS, FW (water-soluble Cd), FNaCl (pectates and protein Cd), FHAc (undissolved Cd phosphate) and lactose concentrations, and also induced the expression of genes encoding metal transporters in roots. Overall, NH4+-N differently regulated Cd uptake and accumulation in DPW seedlings in the absence or presence of NO3-N, while NO3-N greatly increased Cd uptake and accumulation in the presence of NH4+N compared to the absence of NH4+-N. These patterns of Cd alteration likely arose due to different N forms altering Cd subcellular distribution and chemical forms, lactose concentration and the expression of metal transporter genes.