Effects of Temperature on the Deep Supercooling Characteristics of Dormant and Deacclimating Sweet Cherry Flower Buds

Abstract

Seasonal changes in the temperature of the median low-temperature exotherm (LTE50) of dormant sweet cherry (Prunus avium L. cv. Bing) flower buds were significantly correlated with the preceding minimum air temperature in the orchard and the water content of the flower primordia. When buds were exposed to temperatures just below the high temperature exotherms, water migrated from the primordia to the bud scales. Under these conditions, the LTE50 decreased almost 5°C during the first day, but only 1°/day thereafter. The minimum LTE50 was near −32° after the buds were frozen for 10 days. Thawing buds at 0° or above increased the LTE50 about 1°/hr, to −20° to −21°. The LTE50 did not increase above these temperatures until the buds were exposed to 20° for 1-2 days following the completion of rest. During deacclimation, both the LTE50 and temperature range of the low temperature exotherms (LTEs) increased. These changes were accompanied by fluctuations in the capacity of the flower buds to exhibit deep supercooling, expressed as the fraction of an LTE produced per flower primordium (LTE/primordium). Even on days when the LTE/primordium was low, the temperature required to injure 50% of the flower primordia was similar to the LTE50.

Susceptibility of Blackberry Tissues to Freezing Injury after Exposure to 16C

“…Deacclimation at warm temperatures following rest has been studied extensively in 'Elberta' peach [Prunuspersica (L.) Batsch] and 'Bing' cherry (P. avium L.) (Andrews and Proebsting, 1987;Edgerton, 1954;Proebsting, 1963;Proebsting and Mills, 1972). In peach, a maximum temperature at which 50% of the buds are killed (LT50) is attained early in the dormant period (Proebsting, 1963).…”

“…Even when exposed to air temperatures above freezing, the LT50 does not rise above the " minimum hardiness level" (MHL) until after rest completion. Andrews and Proebsting (1987) reported that floral primordia in cherry buds had a median low temperature exotherm (LTE50) when subjected to differential thermal analysis that was correlated with the LT50. The LT50 varied only slightly from the MHL when buds collected in December were held at 20C for 10 days.…”

Metabolomic changes in crown of alfalfa (Medicago sativa L.) during de-acclimation

“…There is some controversy regarding the relationship between the water content and cold hardiness. For example, the water content of winter wheat and rye ( Secale cereale L.) crowns increases throughout the de-acclimation period 24 , 25 , whereas the opposite change has been reported for Rhododendron japonicum and Prunus avium 26 , 27 . Soluble sugar levels decrease during de-acclimation as carbon losses exceed carbon gains at slightly elevated winter temperatures 5 .…”

Effect of Thawing Time, Cooling Rate and Boron Nutrition on Freezing Point of the Primordial Shoot in Norway Spruce Buds

“…The rate of response depends on the species, organ and physiological stage of the tree. Frost hardiness of wintering buds has been observed to vary according to the ambient air temperature in Norway spruce (Picea abies; Beuker et al, 1997), peach (Prunus persica 'Elberta'; Proebsting, 1963) and sweet cherry (Prunus avium; Andrews and Proebsting, 1987). However, the time constant for hardening and dehardening of forest tree species has not been studied.…”

“…If the time constant for dehardening during thawing is short, as compared with the time constant of hardening during consequent cooling, then the duration of thawing may affect the results of frost hardiness tests. Water flow through the collenchymatic plate is the driving force for rapid dehardening during thawing (Andrews and Proebsting, 1987) and rehardening during recooling. Since cell-wall porosity is one of the factors affecting the water resistance of cell walls (Wisnievski, 1995), B deficiency could also have an effect on rates of dehardening and hardening of dormant buds.…”