WHAT IS IN THE INTERCELLULAR SPACES OF ROOTS - EVIDENCE FROM THE CRYO-ANALYTICAL-SCANNING ELECTRON-MICROSCOPE

The schizogenous intercellular spaces (i.e. those small spaces formed by cell walls coming apart) in the cortex of the roots of field-grown maize (Zea mays L.) were studied in planed transverse faces of frozen tissue, very lightly etched and coated with Al. The spaces were mostly filled with either fluid or, in the drier roots, with a flaky deposit . This deposit may have been left behind when water was withdrawn, or may have been debris dislodged by the planing. Even in roots with most ly dry spaces, some wet, fluid-filled spaces remained. X-ray microanal ysis of the wet spaces revealed that the fluid contained K (average co ncentration 230 mM, range 50-750 mM) and Ca (average concentration 100 mM, range 15 to 550 mM), and occasionally small amounts of S, P or Cl . No other balancing inorganic anions were detected. Concentrations in the wet intercellular spaces showed considerable variation between on e space and the next, and were often quite different from those in the vacuoles of adjacent cells. However, overall the vacuoles of the cell s surrounding the spaces showed mean concentrations, and distributions of concentrations, indistinguishable from those of the wet spaces. An alyses of the deposits in the dry spaces were less reliable because of their uneven surface, but the same ions in about the same amounts wer e found there. The contents of the spaces showed no correlation with e ither the time of collection of the roots, or with distance from the r oot tip. Nor was there any change in concentration of these ions in th e spaces when the roots were grown for 19 h in distilled water mist. E xperiments and evidence are presented suggesting that the observed dis tribution of ions is probably not an artefact. Pilot experiments showe d similar distributions of extracellular ions in roots of barley, Suda n grass and soybean.