INVESTIGATION OF MACROMOLECULE ORIENTATION IN DRY AND HYDRATED WALLS OF SINGLE ONION EPIDERMAL-CELLS BY FTIR MICROSPECTROSCOPY

Polarised infrared spectra from the wall of a single epidermal onion c ell were obtained using a Fourier transform infrared (FTIR) microscope . The use of a newly constructed hydration cell allowed studies of bot h composition and architecture of intact walls of single hydrated plan t cells. By comparing spectra taken with infrared light polarised perp endicular, or parallel, to the long axis of the cell, orientations of macromolecules in dry and hydrated cell walls were investigated. It wa s observed that bands associated with pectin were stronger with polari sation perpendicular to the direction of the cell elongation. On the o ther hand, bands associated with cellulose were more intense with pola risation parallel to the direction of cell elongation. These results s how that in dry and hydrated cell walls, not only was there a net orie ntation of cellulose, but also of pectin. The implication of this is t hat pectin, which was previously thought to play no structural role in cell walls may, in fact, contribute to the mechanical and structural properties of the cell network. Such results are likely to have a trem endous impact on the formulation of definitive models for the static a nd growing cell wall. (C) 1997 Elsevier Science B.V.