Laboratory Freezing Research Articles

Effect of Protective Covers on Cold Acclimation and Survival of Hybrid Tea Roses1

Abstract Rosa hybrida L. ‘Peace’ and ‘Garden Party’ plants covered with mulch in October and November for 2 weeks were less cold-hardy, based on laboratory freezing studies, than unmulched plants. Subsequently, field injury of mulched stems was observed in December and January. Plants covered in mid-December were less cold-hardy than unprotected plants but exhibited less field injury in January than October- and November-mulched plants. Plants covered with Styrofoam cones were not injured as early as perlite-covered plants. There was no significant difference in winter injury when stems were covered with perlite, soil, or leaves. Unprotected plants had less winter stem injury than covered plants during the winter of 1978–79, when the plants were covered with snow. The following winter there was little snow cover, and November- and December-covered plants had significantly less winter stem injury in January than plants with no cover.

Effects of applied pressure on freezing soils

Background studies illustrating the effect of externally applied pressure on frost heave are reviewed together with some of the thermodynamic aspects of pressure effects. New experimental data are presented to show how the segregation potential varies with applied pressure. This variation is explained in terms of the influence of applied pressure on the segregation-freezing temperature and the average permeability of the frozen fringe. An explanation is given of the change in mode from expulsion to attraction of water to the freezing front in a loaded soil and it is shown that segregation can be eliminated by externally applied loads. However, these loads are generally too high to be of engineering interest. While it has been concluded that, under laboratory freezing conditions, the segregation potential is dependent upon applied pressure, suction at the frost front, and rate of cooling of the frozen fringe, field conditions are often simpler. A simplified method of predicting frost heave under field conditions is developed that should lead to conservative results.

Comparison of Flower Bud Cold Hardiness of Several Cultivars of Rhododendron spp.12

Abstract Five evergreen rhododendron cultivars were compared for flower bud cold hardiness in laboratory freezing studies on 6 dates. ‘Roseum Elegans’, ‘Catawbiense Boursalt’ and ‘Boule de Neige’ were more cold hardy on most sampling dates than ‘America’ and ‘Lee’s Dark Purple’. The relative cold hardiness of these 5 cultivars was consistent on several winter dates over several years. Injured florets were black and readily separated from uninjured white florets upon dissection of the inflorescence bud after freezing.

凍結融解による岩石の破壊過程破壊サイクルの分布特性

The failure process of rocks by freezing and thawing cycles cannot be fully understood. However, it isvery important to confirm this process for the assessment of durability of material rocks for use as riprap ofrockfill dams. The auther has been conducting laboratory freezing and thawing test on material rocks to confirmthis process. From a series of tests, the following results have been obtained.1) The number of freezing and thawing cycles to failure (The auther defined this cycles as freezing andthawing life) shows wide fluctuation and this phenomenon is an essential properties of the failure process ofrocks by freezing and thawing cycles.2) Exponential, log-normal, Weibull, McCall and gamma distributions are all applicable to describe thedistribution characteristics of freezing and thawing lives of rocks.3) From the distribution characteristics of freezing and thawing lives, and the change of physico-mechanicalproperties, it is concluded that the failure process of rocks by freezing and thawing cycles is serial andcumulative like the fatigue failure process of metal.

AVOIDING SUPERCOOLING OF ROOTS DURING LABORATORY FREEZING STUDIES

Supercooling during laboratory freezing may prevent determination of the freezing temperatures that injure roots. Several freezing procedures were tried to prevent supercooling. Forsythia root sections partially imbedded in ice did not supercool, but sections frozen in air in moist greenhouse soil, or wrapped in moist tissue paper supercooled to −2 to −6 °C before freezing. Rate of the temperature drop and use of cold-hardened and nonhardened roots did not affect occurrence of supercooling.

The Effect of Prefreezing on the Strength and Deformation Properties of Granular Soils

The extraction of reliable undisturbed samples of granular soils from below groundwater table for subsequent laboratory testing, is not possible by routine sampling methods. Consequently, during investigations for major, sensitive structures founded on such profiles, alternative sampling techniques such as in situ freezing and coring or dewatering and block sampling followed by laboratory freezing and coring, have to be considered. In both procedures, the soil is frozen at some stage. This paper presents the results of a study of the effect of freezing and thawing of granular soil on its static and cyclic strength and stress-strain behaviour. It is found that freezing and thawing leads to some degradation in the soil properties, but it is still recommended that these procedures may be used to obtain conservative values of the soil properties which are more relevant than those obtained from reconstituted specimens.

Flower cold hardiness: a potential determinant of the flowering sequence exhibited by bog ericads

In laboratory freezing trials, cold hardiness of six types of bog ericad flowers differed significantly (i.e., Chamaedaphne calyculata > Andromeda glaucophylla > Kalmia polifolia > Vaccinium myrtilloides > Ledum groenlandicum > Vaccinium macrocarpon) at air temperatures between −4 and −10 °C but not at temperatures above −2 °C. At the Luther Marsh bog in southern Ontario, low temperatures (−3 to −7 °C) would select against May flowering by the least cold hardy ericads. Availability of pollinators, on the other hand, would encourage May flowering by the most cold hardy species. Presumably, competition for insect pollinators has promoted the diversification of bog ericad flowering peaks, while air temperature, in conjunction with flower cold hardiness, determined the order in which flowering peaks were reached.

凍結融解試験による岩石の劣化特性と耐久性の評価

The prevision or estimation of rock durability is a very important and complex problem in engineering geology and civil engineering. Especially the durability of rocks for use as riprap of fill dams has a close relationship to their safety. The author has been studying on the durability of various rocks for use as riprap of fill dams by means of laboratory freezing and thawing test. As the first step, obtained results are as follows.(1) The deterioration characteristics of rocks are classified into following three types.A: No deterioration occurs in matrix itself. Sudden break to two or more pieces occurs along cracks after repeating certain freezing and thawing cycles.B: Progressive deterioration occurs in matrix itself. Exfoliation from the surface of test pieces occurs at any freezing and thawing cycles.C: Intermediate type between A and B.Type A rocks seem to be durable and no problem will occur for using as riprap of fill dams unless break will occur within the setting cycles. Durability of type B and C rocks can be estimated by the value of weight loss at the setting cycles.(2) Under freezing and thawing test, changes of saturation moisture content, effective porosity, dry density, coefficient of dynamic elasticity and shore hardness have a close relationship to the deterioration characteristics of rocks and can be classified into several patterns.(3) Freezing and thawing should be repeated at least 100 cycles to estimate rock durability. If it continues extra 100 cycles (i. e. 200 cycles), more precise estimation can be done on many deterioration characteristics of rocks, for example, the rate of deterioration. The rocks that weight loss occur less than 10% at 200 cycles are very durable and seem to cause no problem using for riprap of fill dams.(4) The durability of rocks can be estimated to some degree from initial value of the physico-mechanical properties. But such method is very rough and sometimes even unreliable. In order to estimate the durability of rocks more precisely, it is necessary to make direct accelerated deterioration experiments such as freezing and thawing test and measure various changes of physical properties.

Critical frost temperatures for Douglas-fir cone buds

Forest temperature for 50% kill (LT50) of female buds as determined by laboratory freezing tests in 1973–1975 ranged between −19 and −23 °C for five clones from mid-December to early March. Hardiness then decreased at 1.6 °C per week to an LT50 of −6.5 °C by the time of first bud swelling in late April. Throughout flowering, LTM remained at −4.5 and LTio at −2.7 °C. Male and vegetative buds were respectively about 1.5 and 4 °C hardier. Preliminary frost protection requirements have been defined so as to ensure 90% female bud survival on 80% of the clones.

Cold Hardiness of ‘Montmorency’ Sour Cherry Flower Buds during Spring Development1

Abstract Laboratory and orchard studies were designed to determine the critical temperatures at which injury to flowers of sour cherry (Prunus cerasus L. cv. Montmorency) occurred during spring development. In laboratory freezing tests, the temperature at which 50% of the flowers were killed (LT50) rose rapidly as the buds swelled, reaching −5°C just prior to separation of the bud scales and −3° at full bloom. Comparison of orchard minima with subsequent injury indicated greater sensitivity of unopened buds, but lower sensitivity of expanding flowers, in comparison with laboratory values. Limited comparisons indicated no consistent effect of previous temperatures upon bud hardiness. On the basis of these observations, growers with orchard heating equipment should not permit temperatures to fall below −2° once buds reach the “water bud” stage (40 to 50 mg fresh weight per bud).

Factors Influencing Winter Hardiness of Flower Buds and Stems of Evergreen Azaleas1

Abstract Two evergreen azalea clones, Rhododendron × ‘Maryann’ and R. poukhanense Levl., were studied in outdoor and controlled freezing experiments during 2 winters. Outdoor experiments revealed that 1) flower bud injury occurred in mid-winter, 2) flower buds of R. poukhanense were less hardy than those of R. ‘Maryann’, 3) splitting of apical stems often accompanied injury in R. poukhanense, and 4) a significant difference existed between the 2 clones in apical stem water percentage during December and January. In the laboratory freezing tests, initial injury occurred in the apical stem pith and at a higher temp than that which injured the flower bud. When twig water content of R. poukhanense was reduced prior to freezing, stem splitting was prevented and the twigs survived exposure to lower temp. Large ice masses were observed in the vascular tissue of R. poukhanense when the frozen twigs were sectioned. Water content and ice crystal development were the primary factors affecting survival of both clones.

Studies on frost injury to wheat. I. Laboratory freezing tests in relation to the behaviour of varieties in the field

Factors influencing the reactions of different varieties of wheat to stem and ear frosting were studied under controlled conditions and in the field. Artificial freezing tests were successful in demonstrating varietal differences in resistance, but these were not always in agreement with behaviour under commercial cultivation. Thus, whereas the American winter wheat Cheyenne showed resistance superior to that of the Australian varieties Bencubbin and Gabo, the observed superiority of Bencubbin over Gabo in the field was not maintained under controlled conditions. A possible explanation for this anomaly lies in the unequal distribution of temperature which obtains within a crop. On several frosty nights the ears and stems of Gabo, owing to their more forward development, were observed to be in a colder zone than those of Bencubbin. These conditions were not reproduced in the freezing cabinet, and comparisons between plants at different stages of growth failed to show any marked change in resistance with age up to the time of ear emergence. The relationship between temperature of freezing and degree of injury was established under different sets of conditions. In one case interaction between the effects of temperature and variety showed that this factor may be of some importance in the interpretation of results of freezing trials.

DISINTEGRATING EFFECT OF REPEATED FREEZING AND THAWING ON BUILDING BRICK*

AbstractLaboratory freezing and thawing tests (A.S.T.M. test No. C47–44 and modifications thereof) were correlated with results of outdoor‐exposure tests. This correlation was based on saturation coefficient, absorption, rate of absorption, strength, and method of manufacture. New York building brick of the soft‐mud and stiff‐mud types were investigated. The results show that those brick within a specific absorption range and with the greatest strength and the smallest saturation coefficient will have lower loss in the freezing‐thawing tests.