Effects of EDTA and Zn Stress on Physiological Characteristics of Medicago sativa L.

[Objectives]The paper was better understand the mechanisms of Zn plant uptake in the presence of EDTA and to evaluate the contributions of Zn-EDTA complexes to Zn uptake.[Methods]Three alfalfa cultivars were cultivated for 60 d before exposure to 0,250μg Zn and 250μg Zn+10μg EDTA per kg soil for 50 d.Zn concentrations in tissues were analyzed by flame atomic absorbance spectrometry.Subsequently,Zn amount per plant,translocation factor(TF)and bio-concentration factor(BCF)were calculated.Nonenzymatic compounds in tissues were analyzed spectrophotometrically.[Results]Application of Zn+EDTA expressively increased biomass of different tissues of three alfalfa cultivars.Among the three alfalfa cultivars,Medicago sativa ssp.displayed the highest Zn concentration in tissues,the largest Zn amount in aerial parts,and the highest BCF in aerial parts under Zn+EDTA exposure.Under Zn+EDTA stress,increases in free proline in roots,stem,and leaves of M.sativa ssp.were found.Inhibited O_(2)^(·-)production in stem and leaves,increases in soluble sugar,but decreases in soluble protein were observed in M.sativa ssp.[Conclusions]M.sativa ssp.is superior to other two cultivars for Zn phyto-remediation,and its well-coordinated physiological changes under Zn+EDTA exposure confer the great Zn tolerance of this cultivar.

Response of Organic Acids to Zinc Homeostasis in Zinc-Deficient and Zinc-Toxic Apple Rootstock Roots

To elucidate the mechanisms of tolerance to zinc (Zn) deficiency and Zn toxicity in the root of apple trees, the apple rootstock Malus hupehensis (Pamp.) Rehd seedlings were selected to study the responses of organic acids to Zn homeostasis in roots under low Zn (0 μmol L-1 ), adequate Zn (as control, 4 μmol L-1 ) and toxic Zn (100 μmol L-1 ) treatments. The differences of Zn concentrations and accumulations in the roots were highest, compared with those in the stems and leaves, when apple seedlings were subjected to low and toxic Zn treatments for 1 d. The concentrations and accumulations of oxalic and malic acids in the roots in the low and toxic Zn treatments increased by 20% to 60% compared with those of the control treatment. Significantly negative correlations were found between the total Zn concentrations and the concentrations of oxalic and malic acids in the roots under 1 d of low Zn treatment. However, contrary correlations were found for the toxic Zn treatment. Meanwhile, the maximum influx rates of Zn 2+ under low and toxic Zn treatments increased by 30% and 20%, respectively, compared with the rate of the control treatment. Both Zn deficiency and Zn toxicity increased the concentrations of organic acids in root after short-time Zn treatment, which could resist Zn stress through balanding Zn homeostasis in M. hupehensis Rehd.