Résumé
The use of temporary immersion in a liquid medium has been shown to improve plant micropropagation both for quality and economical aspects. The efficiency of the system originates in the improvement of nutrionnal and gazeous exchanges. Periods of immersion should be very brief and were easily controlled by a quick displacement of liquid through the application of an overpressure. According to the species and the multiplication process different systems were developped. Meristem proliferation (#Ananas#, #Musa#, #Saccharum#, #Xanthosoma# or microtuberisation (#Solanum#) was performed in large double vessels with an alternative transfer of the medium from one to the other. Rates of multiplication were far better that those obtained on semi-solid medium. For somatic embryogenesis more precise conditions are required and large volumes are not necessary. A specific apparatus was designed allowing for the expression, development and germination of embryos in the same vessel with very simple manipulations. Depending on the species (#Coffea#, #Hevea#, #Musa#) 1000 to 10000 embryos were obtained in a one liter vessel. The quality of the planlets allows a direct transfert to the nursery for growing and hardening. (Résumé d'auteur)