Freeze‐substitution of plant tissues with a new medium containing dimethoxypropane*

SUMMARY Meristematic cells from root tips of Dahlia variabilis (L.) and highly vacuolated storage parenchyma cells of Helianthus tuberosus (L.) were fixed by the high‐pressure freezing technique and freeze‐substituted. A new water‐free medium for freeze‐substitution was developed to obtain better preservation of the ultrastructure of plant tissues. Adding dimethoxypropane (DMP) to the substitution medium gave two positive results: (1) water could be withdrawn from the samples without an exchange of the medium and without adding drying agents or working in a nitrogen atmosphere, and (2) the ultrastructural preservation of the substituted tissues was better than in a methanol medium and at least as good as in tissues fixed chemically at room temperature.