Regulation of frost resistance during cold de-acclimation and re-acclimation in oilseed rape. A possible role of PSII redox state

Regulation of frost resistance during cold de-acclimation and re-acclimation in oilseed rape. A possible role of PSII redox state

2002

A:PS

A possible role of photosynthetic apparatus during cold deacclimation was studied in oilseed rape (Brassica napus var. oleifera). Plants of spring (Star) and winter (Gorczanski) cultivars were cold acclimated at +5?, and de-acclimated during 4 weeks at combinations of +12 and +20? operating in the light or/and dark, with a 12-h photoperiod. Evidence is presented that the photosynthetic apparatus may be involved in temperature perception during de-acclimation. De-acclimation was faster under a 20/12? (day/night) treatment than under the reverse 12/20? (day/night). De-acclimation rate was constant when the day temperature was constant, irrespective of the night temperature both under cold day temperature regimes (12/20, 12/12? (day/night)) and warm-day treatments (20/12, 20/20? (day/night)). The fast decrease in frost resistance observed under warm-day de-acclimation was always accompanied by an acceleration of elongation growth. In the spring cultivar, elongation growth increased starting from the second week of de-acclimation, regardless of temperature conditions. Once elongation growth had commenced during de-acclimation, it continued throughout the period necessary for re-acclimation to low temperature. Re-acclimation to the initial freezing tolerance level was only possible when plant elongation was reduced. In addition re-acclimation of the photosynthetic apparatus to low temperature was impossible in fast growing plants. A possible relationship between PSII, growth rate and frost resistance during cold acclimation and de-acclimation is discussed.

v.115(2):236-243, PHYSIOLOGIA PLANTARUM

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