|Authors: ||H. Imanishi, T. Suzuki, K. Masuda, T. Harada|
|Keywords: ||Lonicera caerulea L., cold acclimation, freezing tolerance, raffinose family oligosaccharides|
Cold acclimation affected the freezing tolerance and soluble sugar composition of the shoot apices of field-grown plants and of the nodes, internodes and calli derived from in vitro-cultured plantlets in Lonicera caerulea L. var. emphyllocaryx Nakai.
The LT50 of the shoot apices fell from –18°C on 10 October to -40°C on 16 December, indicating an increase in freezing tolerance; it remained below -40°C throughout the winter, and rose again from 16 March to 21 June.
Raffinose and stachyose accumulated rapidly from 23 September to 18 December, whereas total soluble sugars and sucrose levels markedly increased from 24 June to 23 September.
The glucose and fructose levels showed them to be independent of seasonal changes in temperature.
The in vitro-grown plantlets and calli were acclimated to low temperature by incubation at 5°C for 1 week and subsequently at 0°C for 1 week.
The freezing tolerance of nodes, internodes and calli gradually rose through more than 12 days of acclimation, while nonacclimated explants could not survive -7.5°C freezing.
Cold acclimation conspicuously changed composition of soluble sugars.
Raffinose accumulated in the tissues, whereas the levels of sucrose, fructose and glucose went unaffected.
These results suggest that raffinose and/or stachyose might play an important role in the freezing tolerance increase in L. caerulea tissues.
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