Supercooling in Overwintering Azalea Flower Buds

Abstract

ABSTRACT

Relationship of the Low Temperature Exotherm to Apple and Pear Production in North America

“…Vers le milieu de I'hiver, on a pr6lev6 des segments de jeunes rameaux de trois cultivars de pommetiers d6coratifs (Malus sp. ) (George et al 1974b;Graham l97l) and Prunus flower primordia (Quamme 1914); and apple (Quamme et al l912a,b) and blueberry xylem (Quamme et al 1972c) which were associated with injury. Differential thermal analysis (DTA) and thermal analysis of apple xylem (Quamme et al l972a,b) and azalea flower primordia (George et al 1974b;Graham 197l) revealed that the exotherm was produced by the freezing of a water fraction which had all the physical characteristics of being supercooled.…”

“…Differential thermal analysis (DTA) and thermal analysis of apple xylem (Quamme et al l972a,b) and azalea flower primordia (George et al 1974b;Graham 197l) revealed that the exotherm was produced by the freezing of a water fraction which had all the physical characteristics of being supercooled. Nuclear magnetic resonance measurements provided direct evidence that the low temperature exotherm was caused by freezing of water in the supercooled state (George et al 1974b).…”

“…(Quamme etal. 1972b The low temperature exotherm in the xylem appears to be produced by a supercooled water fraction (George et al 1974b;Quamme et al 1972b (Rasmussen and McKenzie 1972; George et al 1974a). The lowest temperature at which supercooling in plant tissue has been observed was -47 C in xylem of Fraxinus nigra Marsh (George et al 1974 …”

Use of Thermal Analysis to Measure Freezing Resistance of Grape Buds

“…The flower buds of Vac-cinium corymbosum L. (Biermann et al 1919), Rhododendron sp. (George et al 1974;Graham and Mullin l9l6), and several Prunus species (Quamme 1974;Raja-shekar and Burke 1978; Quamme et al 1982) avoid freezing injury by deep super-cooling. This mechanism of freezing survival has also been exhibited by dormant buds of several Viris species (Pierquet and Stushnoff 1980;Andrews et al 1984).…”

Physiological responses to low temperature

“…According to Quamme (1985), starch in the tissue may retain water within the cell during freezing until the point of homogeneous nucleation is reached. In floral primordia of azalea (George et al, 1974), in peach flower buds (Ashworth, 1982), and in winter buds of some conifers (Sakai, 1978), certain morphological features of the buds seem to be essential for supercooling.…”