Oxaziclomefone, a new herbicide, inhibits wall expansion in maize cell-cultures without affecting polysaccharide biosynthesis, xyloglucan transglycosylation, peroxidase action or apoplastic ascorbate oxidation

Background and Aims Oxaziclomefone (OAC), a new herbicide, inhibits cell expansion, especially in roots and cell-cultures of gramineous monocots. OAC does not affect turgor in cultured maize cells, and must therefore inhibit wall-loosening or promote wall-tightening. Methods The effects of OAC in living cultured maize cells on various biochemical processes thought to influence wall extension were studied. Key Results OAC did not affect C-14-incorporation from d-[U-C-14]glucose into the major sugar residues of the cell wall (cellulosic glucose, non-cellulosic glucose, arabinose, xylose, galactose, mannose or uronic acids). OAC had no effect on C-14-incorporation from trans-[U-C-14]cinnamate into wall-bound ferulate or its oxidative coupling-products. OAC did not influence the secretion or in-vivo action of peroxidase or xyloglucan endotransglucosylase activities-proposed wall-tightening and -loosening activities, respectively. The herbicide did not affect the consumption of extracellular l-ascorbate, an apoplastic solute proposed to act as an antioxidant and/or to generate wall-loosening hydroxyl radicals. Conclusions OAC decreased wall extensibility without influencing the synthesis or post-synthetic modification of major architectural wall components, or the redox environment of the apoplast. The possible value of OAC as a probe to explore aspects of primary cell wall physiology is discussed.