Structural features of cell walls from tomato cells adapted to grow on the herbicide 2,6‐dichlorobenzonitrile

Evidence from high‐resolution images of primary cell walls suggests that the cell wall is constructed from at least two independent yet coextensive fibrous networks, one based on cellulose/hemicellulose and the other on pectin. The ability to analyse the structure of each of these networks in isolation has been hampered by a lack of suitable biological material such as mutants. However, the recent use of the cellulose‐synthesis inhibitor 2,6‐dichlorobenzonitrile (DCB) that prevents the formation of the cellulose‐xyloglucan network while allowing the pectin network to form a functional wall offers the unique opportunity of studying at least the pectin network independently. A range of electron microscopy techniques and a novel spectroscopy method are used to study the walls from tomato suspension cells adapted to growth on DCB. Measurements of the minimum cell wall thickness derived from thin sections of dehydrated walls show that the marked reduction in level of the cellulose/hemicellulose network affects neither the thickness of the wall formed, nor the apparent spacing of pectin molecules. However, images obtained by the fast‐freeze, deep‐etch, rotary‐shadowed (FDR) replica technique show that the three‐dimensional architecture of these pectin‐rich walls is very different from that of nonadapted walls. Fourier transform infrared (FTIR) microspectroscopy data and immunogold‐labelling studies provide additional evidence that supports the previous biochemical data. 1994 Blackwell Science Ltd