Histo-cytological changes in Pelargonium apices during the cryopreservation process: Effect of the osmotic agent chosen for the preculture step

Abstract

International audienceApex cryopreservation studies were undertaken to guarantee the safe, long-term conservation of a Pelargonium collection. Plant regrowth was obtained with a modified encapsulation-dehydration process. Choosing P. x peltatum 'Balcon Lilas' as a model, the main objective was to determine if sucrose is specific in conferring dehydration tolerance to apices. In the preculture medium sucrose was replaced by glucose, glucose with 3% sucrose, or sorbitol at similar osmolarities. None of the osmotic agents tested produced a level of tolerance to desiccation as high as that of sucrose. A high concentration of glucose was toxic and did not induce a dehydration tolerance. A histo-cytological study was performed on apices precultured with the various osmotic agents. Starch accumulation was only observed in most of the apex cells following sucrose preculture, not with the other osmotica. Other important differences concerned nucleus aspect, nucleolus presence, cell plasmolysis and cytoplasm constitutio