EFFECTS OF PREGROWTH AND FREEZING CONDITIONS ON THE RESISTANCE OF MERISTEMS OF DATE PALM (PHOENIX-DACTYLIFERA L VAR BOU STHAMMI NOIR) TO FREEZING IN LIQUID-NITROGEN

Optimal cryoprotection and freezing conditions were studied for date palm meristems. A 1- or 3-day culture period on standard medium, immediately after their dissection, prior to pregrowth on medium containing 0.5 M sucrose, was necessary in order to obtain the survival of meristems after freezing in LN. The maximal survival was reached after cryoprotection with 0.5 M sucrose and 5 to 15 % DMSO, followed by freezing at 1-degree-C.min-1 to -30-degrees-C before immersion in LN.