Cold Hardiness and Acclimation Intensity in Flower Buds for Fall Bloom and Spring Bloom Clones inRhododendron kiusianum, a Dwarf Evergreen Azalea

摘要

The relationship between the degree of cold hardiness (supercooling ability of florets) and the acclimation intensity in flower buds was investigated in the fall bloom and the spring bloom (typical) clones ofRhododendron kiusianum, a hardy dwarf evergreen azalea. Supercooling ability or exotherm temperature distribution (ETD) in florets was determined by differential thermal analysis (DTA) and the intensity of bud acclimation or the rate of deacclimation was judged by the changes in ETD profiles resulting from the dehardening temperature treatment. Although the two clone types showed no significant differences in ETDs and water contents in florets, they differed in their rates of bud deacclimation. The flower buds of fall bloom clones generally tend to deacclimate more quickly than the spring bloom ones throughout the seasons. It is concluded that the degree of cold hardiness in flower buds ofR. kiusianumdoes not differ between the fall bloom and spring bloom clones but the intensity of bud acclimation does; acclimation intensity is higher in the spring bloom clones and the rate of deacclimation is greater in the fall bloom ones.