Nitrogen management of I. lactea var.chinensis in saline-alkali soil

Remediation of contaminated sites through conventional methods is expensive and often applicated to small areas. Phytoremediation (using plants) may be superior to those methods. I. lactea var. chinensis (Iris lactea Pall. var. chinensis (Fisch.) Koidz.), a promising plant for phytoremediation, is usually considered not only tolerant to plant diseases and insect pests but also to cold, drought, shade, trample, salt, and alkali. The objective of this study was to investigate nitrogen management of I. lactea var. chinensis in salt-affected soil, and to provide a scientific data for cultivation. Seedlings under the condition of quartz sand culture were treated with the nine cross combinations of different NaCl concentrations with 0.1(SL), 140(SM), 210(SH) mmol L^-1, and three nitrate nitrogen levels with 0.25(NL), 4(NM) and 8(NH) mmol L^-1. After 35 d of treatment, shoot, root biomass, nutrient uptake in leaves were determined. Compared to 4 mmol L^-1 nitrate, 8 mmol L^-1caused a much higher increase in shoot biomass especially in 140 mmol L^-1 NaCl treatments. At 210 mmol L^-1 NaCl, the exogenous nitrate (NM and NH) caused a 30% increase in shoot biomass, suggesting that exogenous nitrate can significantly increase the salt tolerance of I. lactea var.chinensis, while there were no differences between two exogenous nitrate concentrations. Moreover, Exogenous nitrate resulted in a decrease in root/shoot ratio, but an increase in total N of plant. These results indicate that both the growth and nutrient uptake of I. lactea var.chinensis under NaCl stress were improved by exogenous nitrate.