Development Of Frost Hardiness Research Articles

Frost hardening in white cedar container seedlings exposed to intermittent short days and cold temperatures

Shoot frost hardiness development in white cedar (Thuja occidentalis L.) container seedlings in response to intermittent short days (4 days per week) and warm (not less than 15 °C) or cool (10/5 °C, day/night) temperatures was assessed using the diffusate-electrical conductivity technique. A slight increase in frost hardiness was found within 2 weeks of the start of warm, short days. Frost hardiness increased linearly with time under warm, short days from week 7 to week 14, with seedlings being resistant to damage at −10 °C on week 14. Approximately one-quarter of the seedlings developed brown-green foliage colour after 5 weeks of warm, short day treatment. These seedlings were significantly more frost hardy than the remainder of the seedlings which had dark green foliage. Seedlings exposed to warm, intermittent short days for 13 weeks and then to cool continuous short days for a further 6 weeks became hardy to −20 °C, while seedlings exposed to warm, intermittent short days only for the full 19 week period did not harden to the −20 °C level. Key words: Thuja, day length, photoperiod

Atmospheric CO2 enrichment and the development of frost hardiness in containerized black spruce seedlings

The hypothesis that a relatively brief exposure to elevated atmospheric CO2 could increase the frost resistance of shoots was tested on containerized black spruce seedlings (Piceamariana (Mill.) B.S.P.). Seedlings were exposed to 1000 ppm CO2 toward the end of their second growing season in an unheated production tunnel and in a heated greenhouse. In 1987, continuous 10-week CO2 exposures were applied in conjunction with mineral nutrient fertilization, and freezing tests were conducted each week. In 1988, a series of shorter 2-week CO2 exposures was applied to different groups of seedlings and no mineral nutrients were added. Controlled freezing tests were conducted at −10 °C and were followed by electrolytic conductivity measurements to assess frost injury. Under all experimental conditions, freezing tests on seedlings from both the production tunnel and the greenhouse indicated significantly greater frost damage for the CO2-enriched seedlings than for the controls. Late-growing season CO2 enrichment negatively affected the bud initiation – bud development stage of frost-hardiness development.

Purafil-filtration prevents the development of ozone-induced frost injury: A potential role for nitric oxide

Abstract The relationship between exposure to ozone in the summer and the subsequent development of frost hardiness in the autumn was evaluated in recent experiments with red spruce ( Picea rubens Sarg. Syn. P. rubra ). When O 3 was added to air filtered only through charcoal (contaminated with nitric oxide (NO)), frost sensitivity in late autumn was increased as measured by conductivity from electrocyte leakage. However, when O 3 was added to air filtered through charcoal and Purafil (no NO), no enhancement of frost sensitivity was found. A possible explanation of this difference, involving the chain-propagating property of NO in the O 3 -initiated oxidation of unsaturated hydrocarbons (HCs), is proposed and discussed. N 2 O 5 , which was found to be generated at approximately 0.02 moles per mole of O 3 in the first year's experiment, only marginally modified O 3 toxicity.

Photoperiod control of the initial phase of frost hardiness development in Pinus radiata

Abstract. The development of frost hardiness in Pinus radiata was investigated to establish whether there is quantitative relationship between photoperiod and the hardening process. Three controlled environment experiments were carried out. In the first, seedlings were exposed to a photoperiod that shortened from 13 h at a rate of 3 min d−1 to 9.5 h. At intervals, the photoperiod was either held constant or lengthened. In the second experiment, seedlings were exposed to one of five constant photoperiods between 9 and 12 h for up to 90 d. In the third, seedlings were exposed to photoperiods shortening at rates of 1 or 5 min d−1. Frost hardiness was also measured during the natural photoperiod‐controlled stage of hardening in outdoor‐grown seedlings. Frost hardiness developed at a constant rate in response to a shortening photoperiod once it had declined to about 12 h. This rate was consistent with the hardening rate that occurred in outdoor‐grown seedlings. Hardening stopped when the photoperiod became constant, indicating a tight coupling between changes in photoperiod and hardiness development. When the photoperiod was held constant, the extent of frost hardiness was directly dependent on the photoperiod but the rate of hardening was apparently independent of the length of photoperiod. However, the rate of hardening was dependent on the rate at which the photoperiod shortened, increasing linearly with increases in the rate of change in photoperiod between 0 and 3 min d−1. These results suggest shortening photoperiods control the first stage of the hardening process by regulating the rate of hardening. Frost hardening was inherently unstable once the maximum hardiness was reached since spontaneous dehardening occurred in spite of the controlled conditions. Dehardening also occurred when the photoperiod was lengthened suggesting that the cue for dehardening to commence was the shift from shortening to lengthening photoperiods.

Ultrastructure of cells in the cambial region during winter hardening and spring dehardening in Salix dasyclados Wim. grown at two nutrient levels

The ultrastructure of cells in the cambial region of Salix dasyclados Wim. (clone 78056) was studied during the development of winter hardiness and the onset of cambial activity in spring. Plants were grown at relative growth rates (RG) of 8% and 12% respectively, resulting in different nitrogen content in the stems. Frost hardiness of the plants was estimated by standardized freezing tests. Plants with a higher nitrogen status ceased growth later and started re-growth earlier in spring than plants with lower nitrogen content. Differences in ability to withstand low temperatures during autumn and spring were found between plants grown in the two nutrient treatments. During the development of frost hardiness in the autumn, the number of meristematic cells in the cambial region decreased. The cessation of meristematic activity was accompanied by cell wall thickening and ultrastructural changes in the cells. Frost hardiness increased from the ability to survive -6° C in October to survival of -80° C at the beginning of December. From November to February the cambial region comprised a layer of 2–3 thick-walled cells with conspicuous ultrastructural features. Starch accumulated in plastids in September, decreased during November to March and then increased again in accordance with changes of frost hardiness. Onset of cambial activity began between the end of March and the beginning of April, as shown by increased vacuolization of meristematic cells and mitotic activity. By April, the starch content had increased and lipolysis was observed. Frost hardiness had decreased, and plants with low and high nitrogen content were able to survive -15° C and -10° C, respectively. After budburst, all axillary shoot parts were damaged at temperatures below-3° C.

Effect of photoperiod and temperature on the development of frost hardiness in three Alnus species

The influence of short day and low temperature on cold acclimation of A. crispa (Ait.) Pursh, A. glutinosa (L.) Gaertn. and A. rubra Bong, was investigated. Two clones of each species originating from in vitro propagation were exposed to three daylength/temperature treatments. Periodically plantlets were exposed to controlled freezing temperature in order to evaluate their level of frost hardiness.Short day (SD) and cold temperature (CT) and long day (LD) and cold temperature (CT) were the most effective treatments for the development of frost hardiness in shoots and roots of the three species tested. Short day (SD) and warm temperature (WT) induced a significant increase in hardiness in shoots of all three species. However, this treatment did not trigger root hardening. A. crispa was found to be the hardiest species followed by A. glutinosa and A. rubra. Intraspecific variation was observed between the two A. glutinosa clones. A glutinosa clone AG8, a Russian provenance, showed a greater freezing resistance than A. glutinosa clone AG2, a German provenance.

Frosthardiness development in Pinus sylvestris: The involvement of a K+‐stimulated Mg2+‐dependent ATPase from purified plasma membranes of pine

Purified plasma membranes were prepared from needles of Scots pine (Pinus sylvestris L., Provenance Sodra Ydre), and the behavior of a K+ stimulated Mg2+‐dependent ATPase was studied. The microsomal fraction (1000‐30 000 g) was used for partition in a dextranpolyethylene glycol two‐phase system. Both upper and lower phases were washed twice with new upper and lower phase, respectively, yielding the fractions U3 and L3. After staining with STA (silicotungstic acid) and examining with an electron microscope, an enrichment of the plasma membranes in the U, phase was seen. This fraction was also enriched in K+ stimulated Mg2+‐dependent ATPase. The ATPase was rather specific towards ATP compared to other nucleosides, and had a pH optimum between 6 and 7. The activity of this ATPase was followed during a frost hardening‐dehardening cycle and showed an increased activity towards the end of the hardening period, whereas the activity decreased to normal during the dehardening period.

Involvement of Abscisic Acid in Potato Cold Acclimation

Upon exposure to 2 degrees C day/night (D/N), leaves of Solanum commersonii (Sc) began acclimating on the 4th day from a -5 degrees C (killing temperature) hardy level to -12 degrees C by the 15th day. Leaves of S. tuberosum L. (St) cv ;Red Pontiac' typically failed to acclimate and were always killed at -3 degrees C. Leaves of control (20/15 degrees C, D/N) and treated plants (2 degrees C, D/N) of St showed similar levels of free abscisic acid (ABA) during a 15-day sampling period. In treated Sc plants, however, free ABA contents increased 3-fold on the 4th day and then declined to their initial level thereafter. The increase was not observed in leaves of Sc control plants.Treated St plants showed a slightly higher content of leaf soluble protein than controls. In Sc, leaves of controls maintained relatively constant soluble proteins, but leaves of treated plants showed a distinct increase. This significant increase was initiated on the 4th day, peaked on the 5th day, and remained at a high level throughout the 15-day sampling period.Exogenously applied ABA induced frost hardiness in leaves of Sc plants whether plants were grown under a 20 degrees C or 2 degrees C temperature regime. When cycloheximide was added to the medium of stem-cultured plants at the beginning of 2 degrees C acclimation, or at the beginning of the ABA treatment in the 20 degrees C regime, it completely inhibited the development of frost hardiness. However, when cycloheximide was added to plants on the 5th day during 2 degrees C acclimation, the induction of frost hardiness was not inhibited. The role of ABA in triggering protein synthesis needed to induce frost hardiness is discussed.

Temperature Regulation of the Development of Frost Hardiness in Pinus radiata D. Don

The development of frost hardiness in seedlings of P. radiata was followed using a photoperiod of 9 h and a constant day temperature of 12°C. The seedlings were preconditioned to a night temperature of 6.5°C for 35 days and 4°C for 7 days. The temperature was then reduced to -4°C for 66 days in one hardening treatment (designated 12/-4°C) and to 3°C for 136 days in another (designated 12/3°C). At the end of those periods, the night temperature was increased back to 6.5°C for a further 15 days. Frost hardiness was determined at regular intervals by exposing the seedlings to a series of artificial frosts. During the low temperature regime, frost hardiness developed continuously in seedlings from both treatments, from -5 to -9.5°C in the 12/3°C treatment and to -16.5°C in the 12/-4°C treatment. The rate of development of frost hardiness was constant at constant temperatures. Using a temperature response model, specific rates of hardening were estimated for both this and an earlier experiment, and found to be approximately linear against temperature. The analysis establishes that temperature controls the hardening process of P. radiata by regulating the rate of development of frost hardiness. Frost hardiness was also shown to be related to thermal time. Before this relationship could be useful in predicting frost hardiness of field-grown seedlings, the relative contribution of the photoperiod-induced and temperature-induced hardening in natural environments needs to be more clearly defined.

Accumulation of Free Fatty Acids during Hardening of Chlorella ellipsoidea

Chlorella ellipsoidea Gerneck (IAM C-27) was synchronously grown, and cells at an intermediate stage in the ripening phase of the cell cycle were hardened at 3 degrees C for 48 hours. A nonpolar lipid which increased greatly during hardening was analyzed by gas-liquid chromatography. Palmitic, oleic, linoleic, and linolenic acids were the main components of the lipid. Electron micrographs revealed the appearance of lipid bodies in hardened cells. When formation of free fatty acids and lipid bodies was inhibited with cycloheximide, oligomycin, and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, the development of a high level of hardiness was always inhibited. However, the converse results were not always realized. Cells hardened in the dark in the absence of glucose developed a measurable hardiness in spite of their failure to form free fatty acids. The appearance of lipid bodies was invariably accompanied by the formation of the fatty acids. In pulse-labeling with [(14)C]NaHCO(3) for 4 minutes at zero time and at the 12th hour of hardening, initial incorporation rates of (14)C into total lipids of whole cells and the cellular membrane fraction were significantly higher than that into free fatty acids. These results suggest that, although fatty acids are inserted into membrane lipids during hardening, the accumulation of free fatty acids and the appearance of lipid bodies per se are not involved in the development of frost hardiness.

Vegetative growth and frost hardiness of cloudberry (Rubus chamaemorus) as affected by temperature and photoperiod

The effect of photoperiod and temperature on growth and induction and development of frost hardiness in cloudberry (Rubus chamaemorus L.) was examined in two experiments. The photoperiods were 8, 12 or 24 h and the temperatures were 18, 15, 12, 9, 4, 3, –3 or –4°C depending on the experiment. The level of hardiness was expressed as LT66 or LT50 (the lethal temperature for 66 or 50% of the plant material) for percentage of bud break and for the degree of coloring by triphenyltetrazolium chloride for rhizomes. The vegetative growth was clearly affected by daylength; petiole elongation, leaf growth, shoot dry weight and number of shoots per plant were all reduced under short days compared with long days. However, the photoperiod had no significant effect on hardening of buds or rhizomes. Hardening increased with successively decreasing temperatures. To get the maximum hardiness, plants had to be exposed to freezing temperatures.

Effect of Photoperiod, Night Temperature, and Frost Incidence on Development of Frost Hardiness in Pinus radiata

The role of photoperiod, night temperature, and frequency and severity of frosts on the development of frost hardiness in seedlings of Pinus radiata was studied using controlled environment treatments. In one experiment the specific effects of 9 and 14 h photoperiods and 5 and 15°C night temperatures were examined. In a second experiment, seedlings were sequentially hardened under two simulated early autumn to late winter climates, with the photoperiod and day/night temperatures progressively altered at 11 and 21 day intervals respectively. In addition, half of the seedlings raised in each simulated climate were exposed concurrently to a conditioning frost regime. Frost hardiness of the seedlings in each sequence was determined at regular intervals using a series of evaluation frosts. Frosts of between -3 and -5°C were the most effective factor in controlling the development of frost hardiness. Night temperatures as low as 1°C were also effective but not those above 5°C. A minimum photoperiod requirement of less than 11 h for up to 42 days exposure was required for low-temperature hardening. There appeared to be a response lag in the development of frost hardiness once the critical photoperiod and inductive night temperatures had been imposed. Differences between nursery sites in frost hardiness of seedling stock were attributed to differences in their environments, particularly the incidence of frosts. The final maximum frost hardiness varied between the treatments from - 7.5 to -19°C indicating that Pinus radiata has a greater potential to develop frost hardiness than was previously thought from field observations.

Frost hardiness development in Pinus silvestris seedlings in response to fertilization

The effects of different levels of nitrogen on freezing survival, the amounts of chlorophylls and β‐carotene, the ratios Chl a/Chl b, and (Chl a + Chl b)/β‐carotene in hardened and unhardened seedlings of Scots Pine (Pinus silvestris L.) have been investigated. There was. no correlation between frost hardiness and nitrogen content in the unhardened seedlings. However, the hardy seedlings with the highest nitrogen content, showed a decrease in frost hardiness of 3°C. The amounts of chlorophylls and β‐carotene increased for all the treatments during hardening, except for the seedlings that had the highest nitrogen content; so that the effect of fertilizer was more evident in non‐hardened than in hardened plants. The ratios Chl a/Chl b decreased during hardening in all the treatments. This was an effect of a larger increase of Chl b than Chl a. The ratios of Chl a + Chl b/β‐carotene also decreased during hardening except for the plants that were fertilized with the second lowest amount of nitrogen. Since the amounts of Chl a and Chl b increase during hardening the amount of β‐carotene increases even more.The growth rates of the seedlings were closely related to the nitrogen content for the different treatments. All plants were infected with ectotrophic mycorrhizae, which resulted in an enhancement of ion transportation from the soil to the plants. This is important when the supply of ions is low.

Transition of Lipid Synthesis from Chloroplasts to a Cytoplasmic System during Hardening in Chlorella ellipsoidea

Chlorella ellipsoidea Gerneck (IAM C-27) was synchronously grown and cells at an intermediate stage in the ripening phase of the cell cycle were hardened at 3 C for 48 hours. At various times of hardening, the cells were pulse-labeled for 4 minutes with [(14)C]NaHCO(3) in the light or with [(14)C]glucose in the dark, and the incorporation rate of (14)C into total lipids was determined. A high incorporation rate of [(14)C]NaHCO(3) at zero time of hardening decreased after 6 hours. In the next 15 hours, a distinct increase was noted. This increase occurred prior to the development of frost hardiness. Cycloheximide completely inhibited both the increase and the development, and 3-(3,4-dichlorophenyl)-1,1-dimethylurea remarkably lowered the high incorporation rate at zero time. The incorporation rate of [(14)C]glucose increased along with hardiness in the dark. These results suggest that the major site of lipid synthesis shifts from chloroplasts to a cytoplasmic system during hardening of Chlorella.

Studies on Lipid Changes During the Development of Frost Hardiness in Chlorella ellipsoidea

Studies on Lipid Changes During the Development of Frost Hardiness in Chlorella ellipsoidea

The Influence of Photoperiod and Temperature on the Development of Frost Hardiness in Seedlings of Pinus silvestris and Picea abies

AbstractThe influence of short days and low temperature on the development of frost hardiness in seedlings of Scots pine (Pinus silvestris L.) and Norway spruce [Picea abies (L.) Karst.], grown for 6 months in glasshouses and climate chambers, was investigated. The degree of hardiness was estimated by freezing the shoots of the seedlings to predetermined temperatures. After 8 weeks in a glasshouse the viability of the seedlings was determined by establishing bud flushing.The most effective climate for the development of frost hardiness was short days (SD) and low temperature (2°C); the next most effective was SD and room temperature (20°C). However, long days (LD) and low temperature also had a marked effect on the development of hardiness. A combination of 3 weeks’treatment with SD and 20°C, and 3 weeks with SD and 2°C gave the same results as 6 weeks with SD and 2°C. The results clearly demonstrate the importance of the photoperiod prior to low temperature for the development of frost hardiness.In conclusion both short days and low temperature induce frost hardiness development. Probably this occurs by initiation of different processes in the two cases. The degree of frost hardiness development appears to depend on the sum of these different processes and on the timing between them.

Ultrastructural Differences in Leaf Cells of Some Solanum Species in Relation to Their Frost Resistance

Ultrathin sectioning techniques and morphometric measurements were used to study the ultrastructural differences between Solanum acaule, a frost-resistant potato species, and S. tuberosum `Red Pontiac,' a frost-susceptible cultivar, which had been grown under long-day and warm-temperature conditions and also under cold-acclimating environmental conditions. In general, under long-day and warm-temperature conditions, the cell wall of S. acaule is about twice as thick as that of S. tuberosum `Red Pontiac,' and the number of osmiophilic globuli in the chloroplasts of S. acaule is also much higher than that in S. tuberosum `Red Pontiac.' After cold-acclimating treatments, the chloroplasts of S. acaule, which can be cold acclimated, appeared to change very dramatically while the chloroplasts of S. tuberosum `Red Pontiac,' which cannot be cold acclimated, did not change significantly. The increase in the number of osmiophilic globuli and the disappearance of starch grains in the chloroplasts were associated with the development of frost hardiness in the leaf cells of S. acaule.

Carbohydrate Metabolism and Frost Hardiness in Pine and Spruce Seedlings Grown at Different Photoperiods and Thermoperiods

AbstractLarge changes occur in carbohydrate contents of pine (Pinus silvestris L.) and spruce (Picea abies (L.) Karst.) seedlings cold‐hardened by photoperiod or by combined photo‐ and thermo‐period. The largest change is in sucrose content, which is almost doubled after six weeks short‐day (6/18 h) treatment; and more than doubled (spruce) or more than tripled (pine), when also temperature is lowered (10/5°C). Development of frost hardiness is strongly correlated with the change in carbohydrate contents. At dehardening, the carbohydrate content decreases rapidly, especially in pine, and the raffinose formed during the rest period disappears within 2–4 weeks. Frost hardiness decreases in parallel.The content of soluble carbohydrates may thus play a role in frost hardiness, although it is not the only factor. Bud formation at cold acclimation is not directly correlated with the changes in carbohydrate content and hardiness.

Frost-Hardiness Development in Pinussilvestris L. Seedlings at Different Levels of Potassium and Calcium Fertilization

The influence of potassium and calcium contents on frost-hardiness development of 6-month-old seedlings of Pinussilvestris L. was investigated. The frost hardiness was determined by cooling the shoots of the seedlings at a rate of 1 °C per minute. There was no correlation between frost-hardiness development and potassium content, calcium content, or the ratio of potassium to calcium content.

Frost Hardiness Development in Rapid- and Slow-growing Norway Spruce Seedlings

Frost hardiness development was investigated in rapid-growing and slow-growing 5- to 6-month-old seedlings of Piceaabies (L.) Karst. The different growth rates, resulting from different fertilization without changing the tissue nutrient concentration, had no effect on development of frost hardiness.