Comparative physiology of deacclimation in Hydrangea species differing in cold hardiness
(2011) 9th International Plant Cold Hardiness Seminar (9th IPCHS) — Location: Luxembourg, Luxembourg (17.July.2011)
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- Temperate winters are becoming progressively milder due to global warming, and temperature patterns are becoming increasingly irregular with risk of warm spells. Warm spells may cause premature deacclimation, thereby increasing the risk of subsequent freezing injury. To elucidate the mechanisms behind loss of plant cold hardiness we studied deacclimation in two Hydrangea species differing in mid-winter cold hardiness under natural conditions as well as in response to simulated warm spells. In both H. paniculata, the mid-winter hardier genotype, and H. macrophylla small fluctuations in air temperature during late winter and spring had a direct effect on cold hardiness of stems, whereas the long-term effect of increased temperatures caused a sigmoid deacclimation pattern. The timing of deacclimation was approximately synchronized in the two species, while H. paniculata deacclimated faster than H. macrophylla. This implies that greater risk of frost injuries in H. macrophylla than in H. paniculata is not due to earlier or faster deacclimation in the former than the latter species, but is merely a result of the relative lower absolute cold hardiness of H. macrophylla during mid-winter and spring. Temperature alterations drive or, at least, are closely related to carbohydrate catabolism, which is an important component of deacclimation physiology in Hydrangea. Significant differences in accumulation patterns of specific soluble carbohydrates between H macrophylla and H. paniculata indicated contrasting species-specific responses; including the possible involvement of 1-kestose, heretofore not implicated in freezing tolerance of woody perennials. A recent, more detailed study of H. paniculata revealed that, in addition to changes in carbohydrate metabolism, loss of freezing tolerance is also associated with significant changes in the bark proteome and in the biophysical nature (free, bound) of water in stems. Using two-dimensional difference gel electrophoresis (DIGE) ca. 100 spots were identified differing significantly in abundance in the bark of H. paniculata during deacclimation and showing a clear seasonal separation. A large number of these proteins are pathogenesis-related proteins, which may play a role in freezing tolerance.
Citations
Pagter, M., Renaut, J., Hausman, J.-F., Lefèvre, I. S., Sergeant, K., Arora, R., Jensen, C. R., Liu, F., Møller, S. M., Bertram, H. C., & Petersen, K. K. (2011). Comparative physiology of deacclimation in Hydrangea species differing in cold hardiness. 9th International Plant Cold Hardiness Seminar (9th IPCHS), Luxembourg, Luxembourg. https://hdl.handle.net/2078.5/43149