Effects of 2,6‐dichlorobenzonitrile on differentiation to tracheary elements of isolated mesophyll cells of Zinnia elegans and formation of secondary cell walls

Abstract

The influence of 2,6‐dichlorobenzonitrile (DCB), an inhibitor of the synthesis of glucans, on the differentiation to tracheary elements of isolated mesophyll cells of Zinnia elegans and the formation of secondary cell walls was investigated. DCB caused a decrease in viability of the cells. The number of tracheary elements and the amount of lignin decreased with increasing concentrations of DCB in the medium. However, lignified tracheary elements were observed even in the presence of 5 μM DCB. In the presence of DCB, peroxidase activity and deposition of lignin were not always restricted to secondary cell‐wall thickenings but were observed all over the walls of tracheary elements. In addition, some of the cells without any obvious cell‐wall thickening were also lignified. The amount of total carbohydrate in cell walls decreased in the presence of DCB but the amount of uronic acids was barely affected. The amount of extracellular polysaccharide (ECP) increased in the presence of DCB. The effect of DCB on the incorporation of radiolabel from [14C]‐glucose into cell‐wall polysaccharides was examined. DCB specifically inhibited the synthesis of cellulose. These results suggest that the increase in the amount of ECP and the aberrant deposition of lignin caused by DCB were results of the perturbation of the assembly of cell‐wall materials caused by interference by DCB in the synthesis of cellulose.