STRUCTURAL-CHANGES IN THE INNER-CORTEX CELLS OF SOYBEAN ROOT-NODULES ARE INDUCED BY SHORT-TERM EXPOSURE TO HIGH-SALT OR OXYGEN CONCENTRATIONS

After a 2 h exposure of intact soybean nodules to high concentrations of NaCl (100 mol m(-3)) or oxygen (80 kPa O-2), morphometric computati ons carried out using an image analysis technique on semi-thin section s showed that both treatments induced a decrease in the area of the in ner-cortex cells, which were then characterized by a tangential elonga tion, In contrast, no significant change in area occurred in the middl e-cortex cells although their elongation decreased. Electron microscop ic observations showed that in the inner-cortex cells changes included the presence of wall infoldings, an enlarged periplasmic space and a lobate nucleus whose chromatin distribution differed from that of the control, Structural changes also occurred in the endoplasmic reticulum , microbodies, mitochondria and plastids. From several of these change s, which are similar to those noted in osmocontractil cells in respons e to external stimuli, it can be hypothesized that the inner cortex ma y provide a potential mechanism for the control of oxygen diffusion th rough the nodules.