title: Permeability of Plant Young Root Endodermis to Cu Ions and Cu-Citrate Complexes in Corn and Soybean.
abstract: The non-selective apoplastic passage of Cu and Cu-citrate complexes into the root stele of monocotyledonous corn and dicotyledonous soybean was investigated using an inorganic-salt-precipitation technique. Either Cu ions or Cu-citrate complexes were drawn into root through the apoplast from the root growth medium, and K4[Fe(CN)6] was subsequently perfused through xylem vessels or the entire root cross section. Based on microscopic identification of the reddish-brown precipitates of copper ferrocyanide in the cell walls of the xylem of corn and soybean roots, Cu(2+) passed through the endodermal barrier into the xylem of both species. When the solution containing 200 μM CuSO4 and 400 μM sodium citrate (containing 199.98 μM Cu-citrate, 0.02 μM Cu(2+)) was drawn via differential pressure gradients into the root xylem while being perfused with K4[Fe(CN)6] through the entire root cross-section, reddish-brown precipitates were observed in the walls of the stele of soybean, but not corn root. However, when a CuSO4 solution containing 0.02 or 0.2 μM free Cu(2+) was used, no reddish-brown precipitates were detected in the stele of either of the two plants. Results indicated that endodermis was permeable to Cu-citrate complexes in primary roots of soybean, but not corn. The permeability of the endodermal barrier to the Cu-citrate complex may vary between dicotyledonous and monocotyledonous plants, which has considerable implications for chelant-enhanced phytoextraction.
authors.affiliation: a College of Life Sciences, Nanjing Agricultural University , Nanjing , China.
authors.forename: Yanzhao
authors.initials: Y
authors.lastname: Fu
authors.forename: Wenrui
authors.initials: W
authors.lastname: Lei
authors.forename: Zhenguo
authors.initials: Z
authors.lastname: Shen
authors.forename: Chunling
authors.initials: C
authors.lastname: Luo
mesh_terms: D001673:Biodegradation, Environmental; D002473:Cell Wall / Q000378:metabolism; D002614:Chelating Agents / Q000378:metabolism*; D002951:Citrates / Q000378:metabolism*; D010539:Permeability; D018517:Plant Roots / Q000378:metabolism; D012989:Soil Pollutants / Q000378:metabolism*; D013025:Glycine max / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism*
chemical_list: D002614:Chelating Agents; D002951:Citrates; D012989:Soil Pollutants; C111995:copper(II) citrate
keywords: Cu ions; Cu-citrate complexes; Endodermis; corn; phytoextraction; soybean