Physiological Study of Freezing Tolerance in Temperature Fruit Trees

다국어 초록 (Multilingual Abstract)

Freeze is one of the important abiotic stresses and it has induced economic losses in temperate fruit crops. For several decades, many studies have reported mechanisms of freezing tolerance (FT). Particularly, in the process of cold acclimation (CA), noticeable changes including dehydration, perturbation of membranes, increase of cryoprotective proteins, accumulation of osmolytes (soluble sugars, proline, polyamines, etc), and enhancement of antioxidant activity have been observed. These changes are controlled mainly by the results of genetic adjustments from the signal perception and transduction, transcriptional regulatory network, to downstream stress-responsive gene expression (ABA-dependent or ABA-independent). More recently, due to abnormal weather caused by global warming, flowering of temperature fruit trees has been gradually accelerated and spring frost damage has consistently increased with cold snap after premature deacclimation (DA). For that reason, many researchers have turned their attention to DA study and have focused on physiological, biochemical, and molecular mechanisms of DA. Strategies allowing plants to survive freezing temperatures have been divided into two categories (Levitt, 1980): 1) FT and 2) freezing avoidance. Ideally, to reduce the risk of frost injury, temperate fruit trees should be deacclimated as slowly or as late as possible during periods of unseasonable warmth in early spring (Rowland et al., 2005). Thus, recent required genotypes or strategies should be not only very hardy to extremely low temperatures, but also adaptable to unexpected changes of temperature or capable of avoiding erratic temperature patterns through deeper and longer dormancy. The presenter has recently performed two different experiments in regard to these two categories and will describe the two experiments with a brief history of FT studies in physiological aspects.