A quantitative investigation of symplasmic transport in Chara corallina. III. An evaluation of chemical and freeze-substituting techniques in determining the in vivo condition of the plasmodesmata

摘要: We present data on a comparison of plasmodesmata in the nodal complexes of Chara corallina prepared for electron microscopy by chemical fixation of specimens at room temperature and those that have been freeze-substituted. The freeze-substitution technique was applied to intact nodal complexes with the internodal cells on either side intact and showed that most plasmodesmata in the cell walls joining a nodal cell with an internodal cell were free of any occluding substance. We feel that the nonoccluded plasmodesma is the in vivo condition and that previous results using chemical fixation at room temperature where occlusions were reported in Nitella translucens and Chara corallina are artifacts of preparation.