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María A. Equiza and David A. Francko

. Therefore, there is a continuous search for suitable species and cultivars ( Broschat and Meerow, 2000 ; Francko, 2003 ). A rapid and accurate quantitative assessment of freezing injury would facilitate the screening of putatively cold-hardy new cultivars

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Julián Miralles-Crespo, Juan Antonio Martínez-López, José Antonio Franco-Leemhuis, and Sebastián Bañón-Arias

freezing injury in leaves. Materials and Methods Plant material and growing conditions. Two experiments were carried out in 2009 and 2010. In both years, plants from rooted cuttings in June of two oleander cultivars ( Nerium oleander L. ‘Yellow’ and ‘Pink

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Edward N. Ashworth

Abstract

Freezing injury is a major limiting factor in the production of horticultural crops. The effects of low temperatures vary and are noted as freezes to the Florida citrus crop; midwinter damage to deciduous fruit crops; frost damage to flowers, vegetables, and developing fruit; and limits to the range of perennial species. It is not the purpose of this paper to review the literature on freezing injury. Several recent books and review articles on the subject already exist (16, 17, 32–35, 50, 65). Instead, the purpose of this paper is to identify basic research areas and opportunities for horticulturists.

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Peter M. Rosen, George L. Good, and Peter L. Steponkus

Abstract

Four cultivars of kurume azalea (Rhododendron sp.), ‘Hersey Red’, ‘Snow’, ‘Coral Bells’ and ‘Hino Crimson’ reported to have different susceptibilities to winter injury in the nursery were compared for their sensitivities to direct freezing injury (both to roots and leaves) and desiccation injury under controlled conditions. Sensitivity to root freezing injury was inversely correlated with winter injury. A positive association between leaf hardiness to freezing injury and resistance to winter injury was found only in ‘Hino Crimson’. Susceptibility to winter injury was most closely associated with desiccation, as indicated by the minimum water potentials under conditions of frozen soil and high evaporative demand.

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Preston K. Andrews, Edward L. Proebsting, and Dennis C. Gross

Abstract

The freezing patterns of flower buds in peach [Prunus persica L.) Batsch ‘Redhaven’] and sweet cherry (Prunus avium L. ‘Bing’) changed significantly during spring deacclimation. Nucleation temperature, measured by differential thermal analysis (DTA), and freezing injury were monitored for reproductive organs as affected by the presence and absence of vegetative tissue, surface moisture, and the ice nucleation-active (INA) bacterium Pseudomonas syringae van Hall. The flower buds retained the capacity to deep supercool until early bud swell, when the low temperature (LT) exotherm distribution widened and fewer LT exotherms were produced. Following the disappearance of the LT exotherms until the petals tips first appeared through the calyx, the nucleation temperature of the flower buds increased 1° to 3°C. During this period the presence of stem tissue had no effect on nucleation temperature, whereas surface moisture increased the nucleation temperature several degrees. After full bloom, flowers attached to the stem froze at higher temperatures than excised flowers whether wet or dry. From the time the flower buds lost the capacity to deep supercool until petal tip emergence, freezing injury was reduced significantly by increasing the ice nucleation temperature, either by wetting peach flower buds or by inoculating sweet cherry flower buds with INA P. syringae bacteria. Following petal tip emergence, the higher nucleation temperatures no longer reduced freezing injury. Apparently, the flower buds of these Prunus species avoid freezing during the winter by deep supercooling of the dormant flowers, yet tolerate freezing during the early stages of flower development in the spring.

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Charles F. Forney, Michael A. Jordan, Kumudini U.K.G. Nicholas, and Jennifer R. DeEll

Use of volatile emissions and chlorophyll fluorescence as indicators of freezing injury were investigated for apple fruit (Malus ×domestica Borkh.). `Northern Spy' and `Delicious' apples were kept at -8.5 °C for 0, 6, or 24 h, and then at 20 °C. After 1, 2, 5, and 7 d at 20 °C, fruit were analyzed for firmness, skin and flesh browning, soluble solid content, titratable acidity, ethanol, ethyl acetate, ethylene, respiration rate, and chlorophyll fluorescence. Freezing caused skin and flesh browning and a loss of fruit firmness, which was greater in `Northern Spy' than in `Delicious'. In `Northern Spy' fruit subjected to the freezing treatments, ethanol and ethyl acetate concentrations were as much as 37- and 300-fold greater, respectively, than in control fruit. `Delicious' fruit showed similar patterns of ethanol and ethyl acetate increase, but of lower magnitude, as a result of freezing. Higher fruit respiratory quotients were associated with increased ethanol and ethyl acetate concentrations. Ethylene production and chlorophyll fluorescence of fruit were reduced by freezing.

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Michele R. Warmund and James T. English

In 1993, ice-nucleation-active (INA) bacteria were isolated from `Redwing' red raspberries (Rubus idaeus L. var. idaeus) at five pigmentation stages. Fruit were also subjected to thermal analysis to determine the ice nucleation temperatures. INA bacteria were recovered from nearly all fruit samples, and the bacterial populations tended to decrease with greater red color development (i.e., fruit maturation). However, the ice nucleation temperature was not affected by the stage of fruit pigmentation. In 1994, INA bacterial densities were similar among fruit at the three pigmentation stages sampled. INA bacteria were recovered more often from the calyx rather than the drupe surface of these fruit. INA bacteria also were detected on pistils of some fruit. Red and pink fruit, which were nucleated with ice, had greater receptacle injury than mottled, yellow, or green fruit, but INA bacterial densities apparently were not related to injury. Thus, the injury response of fruit at different pigmentation (or development) stages indicated that nonbacterial ice nuclei may be involved in freezing injury of developing raspberries.

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M. R. Warmund, M. F. George, M. R. Ellersieck, and J. V. Slater

Abstract

Experiments were performed on ‘Cherokee’ blackberry (Rubus sp.) floral buds and cane tissue collected from field plantings on 12 Jan. and 18 Feb. 1987 to determine the susceptibility of floral primordia, phloem, and xylem to freezing injury after exposure to 16C for 0, 4, 12, 24, or 48 hr. Before rest completion in January, floral primordia, phloem, and xylem subjected to 16C were hardier than those tissues tested in February when rest was completed. Floral primordia and cane tissues dehardened slowly with time at 16C before rest completion. After rest was completed, the rate of deacclimation of floral primordia and xylem increased. Some blackberry canes were subjected to two thawing episodes at 16C for 4 hr. In January, phloem and xylem of canes thawed twice were as hardy or hardier than those tissues in samples thawed once. Conversely, two thawing episodes in February resulted in greater xylem injury than a single episode, but two episodes did not affect the hardiness of the phloem. The number of thawing episodes did not affect floral bud hardiness at either sampling date.

Open access

H. A. Quamme, P. M. Chen, and L. V. Gusta

Abstract

Low temperatures (LT) exotherms were found by differential thermal analysis (DTA) at −30°C in ‘Siberian C’ peach (Prunus persica [L.] Batsch) and −39° in ‘Starkrimson Delicious’ apple (Malus domestica Borkh. Nuclear magnetic resonance (NMR) spectrometry of intact stems and isolated bark and wood revealed that the LT exotherm was produced by freezing of deep supercooled water which was detected in the wood but not the bark. Freezing processes of the wood and bark appeared to be independent. In both species, xylem injury occurred at the same temperature as the LT exotherm and was closely, if not causally related to freezing of the supercooled water. Bark injury also occurred at the same temperature as the LT exotherm and may have been caused by dehydration stress or freezing of a small amount of supercooled water which remained undetected by NMR spectrometry. The dehydration resistance of apple wood on desiccation at 70 to 90% relative humidity was greater than that of the peach wood which in turn was greater than that of the bark of both species. The dehydration resistance of apple and peach wood may involve both nonliving and living elements of the wood because pulverizing the tissue destroyed the effect, whereas heat killing only lowered it. Both supercooling and dehydration resistance may be related to microcapillary pore structure which restricts heterogeneous nucleation and sublimation of supercooled water from the ray parenchyma cells.

Open access

E. N. Ashworth, D. J. Rowse, and L. A. Billmyer

Abstract

The freezing of water within the woody tissues of apricot (Prunus armeniaca L.) and peach [Prunus persica (L.) Batsch] was characterized and the relationship to freezing injury established. Bark and xylem tissues exhibited contrasting freezing patterns and mechanisms of freezing resistance. Water in xylem parenchyma cells deep-supercooled. Tissue injury appeared to result from the freezing of this supercooled water. In contrast, water within bark tissues underwent equilibrium freezing. Bark injury resulted from the stresses which accompany extracellular ice formation and cellular dehydration.