The present paper aimed to evaluate the effects in the physiological, chemical and cellular quality of cryopreserved seeds through different techniques. Onion seeds of the Baia Periforme cultivar were submitted, for one hour, to two cryopreservation techniques. (a) immersion in N2 fluid (-196°C) with cryoprotector (glycerol 50%) and (b) immersion in N2 fluid. After the cryogenization period of time, the seeds were submitted to three thawing methods: (1) room temperature of 25ºC for two hours; (2) water bath (double-boiler) at 37ºC for five minutes; (3) microwave the 70W power for five minutes. Before and after the cryopreservation, the following parameters were assessed: water content, germination, vigour (accelerated aging, first counting, length of root and of the air parts of the plantules), chemical composition (soluble sugar, proteins and starch contents) and analysis of the cell cycle and mitotic index. The immersion in fluid nitrogen, without the use of cryoprotector, is an adequate technique for the cryopreservation of onion seeds that does not alter the germination nor the chemical composition of the seeds, and it was also the treatment that presented the highest number of cells in cell division of all of the melting methods. The cryogenic treatment with the use of glycerol 50% as cryoprotector damaged the physiological quality and altered the chemical composition of the onion seeds. The thawing of the seeds in the microwave is more adequate than thawing at room temperature or in a water bath. However, the last one presented higher mitotic rate than the other treatments.
Allium cepa; storaged; N2 fluid; physiological quality
