Cold pretreatment amplifies the responses of in vitro Eucalyptus grandis shoots to cryopreparative drying.

BACKGROUND

Eucalyptus grandis is an important commercial forestry species in South Africa. Little is known about its response (which is both drought and cold sensitive) to cold exposure and subsequent drying.

OBJECTIVE

The study was to investigate the responses of E. grandis in vitro shoots to cold pretreatment.

METHODS

E. grandis in vitro shoots were subjected to cold pretreatment (5, 10 and 15 degrees C at different exposure periods of 1 or 3 days), different drying times (20, 40, 60 and 80 min over activated silica gel), and the combination of the selected cold pretreatment regime and subsequent drying.

RESULTS

Cold pretreatment alone did not cause detrimental effects but elicited the accumulation of phenolic acids. Shoots exposed to 5 degrees C for 3 days had significantly higher levels of reactive oxygen species as well. The accumulation of ROS and phenolic acids was also noted in unacclimated, dried shoots, especially after 80 min of drying. In addition, these shoots had significantly higher levels of total soluble sugars, lower levels of starch and elevated proline levels.

CONCLUSIONS

This osmotic adjustment strategy was amplified in cold acclimated, dried shoots (10 degrees C, 3 days; 80 min drying), which also had significantly lower levels of ROS, increased levels of phenolic acid, and higher water content and viability.