Influence of diapause and temperature on cryoprotectant synthesis and cold hardiness in pupae of Pieris brassicae

Abstract

1. 1. Cryoprotectant accumulation in pupae of Pieris brassicae was examined as a response to the diapause state and to low temperature exposure. 2. 2. Sorbitol is the major polyol cryoprotectant and occurs in significantly higher concentrations in diapausing than in non-diapausing pupae. Accumulation of sorbitol is apparently triggered as part of the photoperiodically induced diapause state but may be further enhanced by exposure to low temperature. 3. 3. Glycerol is present in all groups, but its consistently low level suggests that it does not function as a cryoprotectant. 4. 4. Diapause pupae have a mean T c only 2°C lower than non-diapause pupae, 24 hr after pupation and low temperature acclimation of diapause pupae does not significantly lower the T c despite the increase in sorbitol concentration. However, non-diapause pupae suffer pre-freeze mortality after exposure to −5°C for 14 days whereas diapause pupae survive — 15°C for up to 30 days. 5. 5. The significance of these results in the understanding of the interrelationships between diapause and cold tolerance in insects is discussed.