Tropical seed species' responses to liquid nitrogen exposure

Abstract

The ability to tolerate ultra-low temperature (-196°C) exposure was evaluated in 66 tropical orthodox seed species of 21 botanical families from the Cerrado (Brazilian Savannah) and Atlantic Forest Brazilian biomes. Liquid nitrogen had no effect on the germinability of 51 seed species. The stimulatory effect of cryogenic temperature on germinability, with or without subsequent chemical scarification, was observed in nine seed species with deep physical dormancy, or heterogeneous levels of seed hardness, or with no dormancy. Significant reduction in germinability occurred in six seed species, presumably because of factors acting individually or in combination on these seeds, such as inappropriate moisture content, or the potentially detrimental effect of rapid cooling (263°C.min-1) or fungal contamination. The results obtained suggest that cryopreservation may be a promising alternative for storing most of the seed species tested.