title: The mechanism of boron tolerance for maintenance of root growth in barley (Hordeum vulgare L.).
abstract: Cultivar differences in root elongation under B toxic conditions were observed in barley (Hordeum vulgare L.). A significant increase in the length and width of the root meristematic zone (RMZ) was observed in Sahara 3771 (B tolerant) when it was grown under excessive B concentration, compared to when grown at adequate B supply. This coincided with an increase in cell width and cell numbers in the meristematic zone (MZ), whereas a significant decrease in the length and no significant effect on the width of the MZ was observed in Clipper (B intolerant) when it was grown under excessive B supply. This was accompanied by a decrease in cell numbers, but an increase in the length and width of individual cells present along the MZ. Excessive B concentrations led to a significantly lower osmotic potential within the cell sap of the root tip in SloopVic (B tolerant) and Sahara 3771, while the opposite was observed in Clipper. Enhanced sugar levels in the root tips of SloopVic were observed between 48 and 96 h after excess B was applied. This coincided with an increase in the root elongation rate and with a 2.7-fold increase in sucrose level within mature leaf tissue. A significant decrease in reducing sugar levels was observed in the root tips of Clipper under excessive B concentrations. This coincided with significantly lower root elongation rates and lower sucrose levels in leaf tissues. Results indicate a B tolerance mechanism associated with a complex control of sucrose levels between leaf and root tip that assist in maintaining root growth under B toxicity.
authors.affiliation: Discipline of Plant and Food Science, School of Agriculture and Wine, Waite Campus, Glen Osmond SA 5064, Australia.
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Choi
authors.forename: Peter
authors.initials: P
authors.lastname: Kolesik
authors.forename: Ann
authors.initials: A
authors.lastname: McNeill
authors.forename: Helen
authors.initials: H
authors.lastname: Collins
authors.forename: Qisen
authors.initials: Q
authors.lastname: Zhang
authors.forename: Bao-Lam
authors.initials: BL
authors.lastname: Huynh
authors.forename: Robin
authors.initials: R
authors.lastname: Graham
authors.forename: James
authors.initials: J
authors.lastname: Stangoulis
mesh_terms: D001895:Boron / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D049108:Cell Enlargement; D049109:Cell Proliferation; D003470:Culture Media; D005838:Genotype; D001467:Hordeum / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018519:Meristem / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D009995:Osmosis; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D043324:beta-Fructofuranosidase / Q000378:metabolism
chemical_list: D003470:Culture Media; D010940:Plant Proteins; D043324:beta-Fructofuranosidase; D001895:Boron