Crioconservação em sementes de cebola

Abstract

The present paper aimed at evaluating the effects in the physiological, chemical and cellular quality of cryopreserved seeds through different techniques. Onion seeds of the Baia Periforme culture have been submitted, during 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 have been submitted to three melting methods: (1) room temperature of 25ºC during two hours; (2) bain-marie (double-boiler) at 37ºC during five minutes; (3) microwave the 70W power during five minutes. Before and after the cryopreservation, the following parameters have been assessed: content of water, germination, vigour (accelerated aging, first counting, length of root and of the air parts of the plantules), chemical composition (content of soluble sugar, proteins and starch) and analyse of the cellular 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 do not alter the germination nor the chemical composition of the seeds, being also the treatment that has presented the highest number of cells in cell division upon all of the melting methods. The cryogenic treatment with the use of glycerol 50% as cryoprotector damages the physiological quality and it alters the chemical composition of the onion seeds. The melting of the seeds in the microwave is more adequate than melting under room temperature or bain-marie. However the last one presented higher mitotic rate than the other treatments.