PIMENTEL, L. W.; http://lattes.cnpq.br/0320052379136072; PIMENTEL, Lívia Wanderley.
Resumo:
Cryogenic storage of seeds is a way of preserving genetic diversity of plant species,
however, for efficient storage of the seed, its physiological quality should be maintained
for the longest period, which depends on prior knowledge of the physiological behavior of
the seed during storage. The objectives was to study the physical properties, hygroscopic
equilibrium moisture, kinetic of cryogenic freezing at different temperatures and moisture
contents, the determination of water content limit for the cryopreservation and
cryopreservation for six months of seed Topaz cotton and peanuts Havana. For the physical
properties determined the actual volume and unity density of the seeds by the method of
measuring the mass of water displaced; bulk density was calculated by the relationship
between seed mass and the volume occupied by these seeds; the porosity, as the ratio
between the bulk density and the unity density; specific heat, thermal conductivity and
thermal diffusivity. seeds containing more than 4, 8, 10, 12 and 14% wb water content
were used, at temperatures of -20 °C (freezer), -60 °C (cryogenic counter), -150 °C
(counter Ultrafreezer) and -196 °C (liquid nitrogen) to the kinetics of freezin. To limit
moisture content to cryoconservation of the seeds were dried and / or humidified to obtain
the levels of 4, 6, 8, 10,12, 14% wb then cryopreserved in liquid nitrogen (-196 ° C) in
nitrogen vapor (-150 °C) in cryo counter (-60 °C) at -20 °C and ambient temperature for a
period of 5 days and submitted after slow thawing, the germination and vigor tests. For
cryogenic storage, seeds were cryopreserved for 30, 60, 90, 120, 150 and 180 days at 25, -
20, 60, -150 and -196 °C and at the end of each storage period, seeds were submitted to the
germination and vigor tests. It was found that one of the thousand seed mass, the water
content in the seeds resulted in a high sphericity. With increasing water content, the unity
density, bulk density and porosity decreased. The equilibrium moisture content of cotton
and peanut Havana Topaz water are directly proportional to the relative humidity and
decreases with increasing temperature for the same amount of equilibrium relative
humidity. Henderson's model modified by Cavalcanti-Mata was best represented the
hygroscopicity of cotton seeds and the Sabbah model for peanut seeds. The curves
obtained for the freezing temperatures of -25, -60, -150 °C and -196 resemble the curve for
freezing a material with a low water content where the kinetics of freezing is expressed by
an exponential curve for thermal diffusivity results within the same water content, there is
an oscillation of these values, but are a set pattern of increased or decreased, with a
consequent temperature variation. The cotton seeds have a TALC from 6 to 8% bu -170 °C
and 8% wb to 196 °C. The peanut seeds so if cryoconservated well at temperatures of -170
° C and -196 °C for a range of water content of 10-12% wb cryogenic storage of cotton
seed and peanut Havana Topaz increased the percentage of germination and seed vigor
studied for 6 months.