Search Results

You are looking at 1 - 10 of 118 items for :

  • artificial freezing test x
Clear All

methodologies will help decide the best course of action and protection strategy before the upcoming freeze. Peach cold hardiness can be measured using the artificial freezing test. The artificial freezing test is commonly accepted as the standard test to

Free access

treatment group. Dehardening and Artificial Freezing Test After 8 weeks, seedlings were moved for conditioning into the greenhouse under spring-like growing conditions to initiate the dehardening process. The average daily maximum and minimum

Free access

Abstract

The relationship between hardiness of flower buds and blossoms, and time of leafing was studied in 25 almond cultivars, species and interspecific hybrids. In artificial freezing tests, genotypes of almond (Prunus amygdalus Batsch) and related species and interspecific hybrids exhibited a wide range of hardiness. A relationship was observed between blossom hardiness and time from leafing to bloom with some exceptions. Results show that genetic sources for blossom hardiness, not necessarily related to time of bloom, exist in these species.

Open Access
Authors: and

Abstract

Dormant twigs of a number of Ericoideae (genera Erica and Calluna) species were collected in midwinter at Gotemba, Shizuoka Prefecture. These twigs were artificially hardened at the temperature from −1 to −3°C for 15 days to increase hardiness and then subjected to controlled test temperatures to assess their hardiness. European ericas were observed to be much hardier than those from South Africa, resisting freezing from −15 to −20°C. South African ericas were hardy only from −5 to −8°C. Calluna cultivars survived freezing down to −30°C.

Open Access

Abstract

Three- to 4-month-old seedlings of an improved selection of Asparagus officinalis L. cv. Mary Washington were artificially hardened and crowns subjected to controlled freezing tests. Two low-temperature acclimation regimes were used. The first was 3C for 0, 1, or 2 weeks before freezing at 0, −5, or − 10C; the second, 3C for 0, 1.5, or 3 weeks, followed by freezing at 0, −2.5, −4.5, −6.5, or −8.5C. Regrowth tests showed that hardiness increased with 2 and 3 weeks of acclimation, with tolerance to −5 and −6.5C, respectively. Water-stressed seedlings (relative water content at 57%) withstood exposure to −5C, but not to −6.5C; rehydrated crowns and well-watered controls were hardy to −3.5C.

Open Access

Hardiness testing of the wood of deciduous fruit trees has been conducted using a variety of techniques. In our studies, the objective was to determine an efficient method of determining freezing injury for apple (Malus × domestica Borkh.) wood. We tested 1-year old wood of two cultivars: Liberty and RedMax. The wood was tested over the course of 2 years (1998 and 1999). Collection began in the late fall and continued throughout the winter (until it was determined full hardiness had been achieved) and then again in the early spring. The wood was cut into 1-cm sections and frozen. The artificial freezing was conducted in an ethanol bath, with the temperature lowered at 5 °C/h. Samples were removed in 3-min intervals. After freezing, the wood was acclimated to 4 °C for 12 h. Three tests were conducted to determine the hardiness/injury to the tissues. The tests used were: discoloration, callus growth and vital staining (with 2,3,5-triphenyltetrazolium chloride). This was a split block design with samples collected randomly from each tree. Four replicates (12 trees) of each cultivar were tested. Results showed that the callus test predicted the same LT50 as the other two tests, discoloration and vital staining. Discoloration was not easy to differentiate and was the most time-consuming. The callus grown by the apple wood was easily formed and distinguished. The callus test does not require the tetrazolium stain; therefore, one less step was needed in comparison to the vital staining test. This reduced testing time by over 6 h.

Free access
Authors: and

Abstract

The croprotectants, polyvinylpyrolidone, glycerol, ethylene glycol and dimethyl sulfoxide were applied individually or in combination with each other in the form of a spray on whole apple (Malus domestica Borkh.) trees in the greenhouse and by terminal feeding apple and pear (Pyrus communis L.) trees in the field. The trees were tested both by artificial and natural freezing. The cryoprotectants increased cold resistance, however, different cultivars showed different effects with the various protective agents. Factors other than the colligative properties appeared to modify the effects of cryoprotectants.

Open Access
Authors: and

Abstract

Cold stress resistance of ‘Redcoat’ strawberries (Fragaria x ananassa Duch.) grown under several fall fertilization nutrient regimes was determined by artificial freezing. Stress resistance was determined at the onset of acclimation, October 15, and in midwinter with fully hardened plants. The least tolerant plants during the onset of acclimation were those with nutrient deficiencies, those with high N and low P and K and those with a high imbalance of K, whereas the most tolerant plants resulted from fertilizer applications of balanced NPK and balanced NPK plus high P (1:2:1). Fully hardened plants, artificially frozen to -9°C, -11° and -13° crown temperature showed similar stress responses to fertilization except that plants given high N plus P and K were more tolerant than in the October freeze test. Tissue analyses showed that plants with the highest ratio of P/K in crown and root tissues were also the most resistant to cold stress.

Open Access

Abstract

Freezing injury of highbush blueberry flower buds (Vaccinium corymbosum L. cv. Rancocas and an experimental hybrid) were investigated after natural freezing and by differential thermal analysis (DTA). Terminal buds were less hardy than median and basal buds on the same twig. Apical, less mature florets were also less hardy than median or basal, more mature florets within each bud. DTA analysis of intact flower buds showed that a rate independent free water exotherm was followed by numerous rate dependent floret exotherms. Floret lethality was associated only with the rate dependent low temperature exotherms. Buds were held over water-glycerol solutions in desiccators so that they came into equilibrium with a relative humidity of 100%, 98% or 96% at 4°C. Artificially hydrated buds were hardy to –10° and artificially dehydrated buds were 15°C hardier. A mean survival temperature of the florets (MSTF) from DTA analysis, derived at slow cooling rates related closely to lowest survival temperature (LST66) from artificial freezing hardiness tests. In mid-winter, under environmental conditions of low temperature and low relative humidity, flower buds of a hardy hybrid lost all DTA exotherms and were hardy to at least –40°. Tissue dehydration and accompanying loss of floret low-temperature exotherms was associated with extreme cold tolerance of blueberry flower buds with the hardy experimental hybrid.

Open Access
Author:

Two-year-old Actinidia vines, grown on their own roots, were subjected to artificial freezing tests in midwinter to determine their relative hardiness. Plant survival, growth recovery, and stem necrosis were used for estimating freezing injury. Actinidia deliciosa (A. Chev.) C.F. Liang & A.R. Ferguson var. deliciosa vines, which included `Abbott', `Bruno', `Greensill', `Hayward', and `Jones' kiwifruit, were all severely damaged by exposure to a temperature of –18C for 4 hours. Actinidia arguta (Sieb. et Zucc.) Planch. ex Miq., A. kolomikta (Maxim. et Rupr.) Maxim., and A. polygama (Sieb. et Zucc.) Maxim. appeared to be more tolerant to winter cold than A. deliciosa, indicating that potential germplasm exists for improvement of cold hardiness through interspecific hybridization.

Free access