Temperature dependence of longitudinal relaxation times (T1) of water protons in flower buds of six azalea species differing in cold hardiness and ecological distribution was investigated by pulse nuclear magnetic resonance spectroscopy. Thermal hysteresis was observed for T1 following a slow freeze-thaw cycle. The T1 ratio (the ratio obtained from the difference between the original T1 value in an unfrozen sample and the final T1 after a freeze-thaw treatment, both at 20°C, divided by the original T1) was closely correlated with the viability of florets in non-acclimated buds of R. kiusianum. If the buds were frozen to a lethal temperature and then thawed to 20°C, the T1 ratio increased. The T1 ratios of acclimated winter buds for the six species used were correlated with the level of cold hardiness (supercooling ability of florets determined by differential thermal analysis). The T1 ratio of deacclimated spring buds, especially those from hardier species, markedly increased upon cooling to a lethal temperature. Species differences observed in acclimated winter buds disappeared upon deacclimation. The T1 ratio appears to be related to the viability of florets and the degree of freezing damage (membrane disruption) in florets.
|Number of pages||7|
|Journal||Plant and Cell Physiology|
|Publication status||Published - Sep 1985|
All Science Journal Classification (ASJC) codes
- Plant Science
- Cell Biology