Cold Deacclimation Research Articles

Examination of Cold Deacclimation Sensitivity of Annual Bluegrass and Creeping Bentgrass

ABSTRACTAnnual bluegrass (Poa annua L.) (AB) frequently exhibits increased susceptibility to winter injury compared to other cool‐season turfgrass species such as creeping bentgrass (Agrostis stolonifera L.) (CB). Interspecific differences in winter survival of these two species may be associated with enhanced sensitivity of AB to decreases in freezing tolerance (deacclimation) during winter and early spring months; however, there is limited understanding of the factors associated with cold deacclimation between these two species. Therefore, the objective of this research was to determine the deacclimation sensitivity of one AB ecotype and one CB cultivar in response to varying temperature increases and durations. Total shoot growth and freezing tolerance (lethal temperature resulting in 50% mortality [LT50]) of AB and CB was monitored throughout cold acclimation (20, 2, and –2°C) and following exposure to a combination of 4, 8, or 12°C for 1 or 5 d. Overall, freezing tolerance of AB (LT50 of –17.7°C) was significantly lower than CB (LT50 of –21.2°C) following cold acclimation, and in general CB maintained higher levels of freezing tolerance throughout deacclimation compared to AB (LT50 of –16.2 and –12°C, respectively). Both AB and CB exhibited deacclimation in response to above‐freezing temperatures; however, the threshold temperature required to induce greater losses in freezing tolerance was lower for AB compared to CB. Specifically, a 2.5‐fold greater loss in freezing tolerance was detected in AB compared to CB following exposure to 4°C. Furthermore, total shoot growth and LT50 were correlated during deacclimation in these species.

Changes in the proteome and water state in bark and xylem of Hydrangea paniculata during loss of freezing tolerance

Appropriate timing and rate of cold deacclimation is a critical component of winter-survival of temperate perennials. However, little is known about the physiological and biochemical changes involved in the deacclimation process. In this study differential expression of proteins in bark and xylem and changes in the quantity and biophysical nature of water in stems of Hydrangea paniculata during deacclimation were investigated. Increasing temperature caused a sigmoid deacclimation pattern in H. paniculata, which was characterized by a distinct decrease in the abundance of several stress- or defence-related proteins, most of which are known to be associated with increased freezing tolerance. In addition to quantitative reduction of stress- or defence-related proteins, proteins changing in abundance during deacclimation mainly fell into the functional categories of carbohydrate and energy metabolism, translation regulation and protein metabolism. Several tissue-specific responses in the accumulation patterns of proteins involved in stress, defence, carbohydrate metabolism or regulation/signalling and structural components were observed between bark and xylem. This indicates different stress responses in the two tissue types or is related to their different structure and functions. Deacclimation of bark was associated with rehydration and a decrease in the accumulation of dehydrins. The latter was correlated with changes in the least mobile stem water fraction, indicating that dehydrins may be involved in binding water in freezing tolerant cells. In xylem, no clear seasonal trend in the content and biophysical nature of water was observed and no dehydrins changing in abundance were identified. The results offer insight into tissue-specific responses during deacclimation of a moderately freezing tolerant woody perennial.

Winter survival and deacclimation of perennials under warming climate: physiological perspectives

Appropriate timing and rate of cold deacclimation and the ability to reacclimate are important components of winter survival of perennials in temperate and boreal zones. In association with the progressive increase in atmospheric CO₂, temperate and boreal winters are becoming progressively milder, and temperature patterns are becoming irregular with increasing risk of unseasonable warm spells during the colder periods of plants' annual cycle. Because deacclimation is mainly driven by temperature, these changes pose a risk for untimely/premature deacclimation, thereby rendering plant tissue vulnerable to freeze-injury by a subsequent frost. Research also indicates that elevated CO₂ may directly impact deacclimation. Hence, understanding the underlying cellular mechanisms of how deacclimation and reacclimation capacity are affected by changes in environmental conditions is important to ensure winter survival and the sustainability of plant sources under changing climate. Relative to cold acclimation, deacclimation is a little studied process, but the limited evidence points to specific changes occurring in the transcriptome and proteome during deacclimation. Loss of freezing tolerance is additionally associated with substantial changes in cell/tissue-water relations and carbohydrate metabolism; the latter also impacted by temperature-driven, altered respiratory metabolism. This review summarizes recent progress in understanding the physiological mechanisms of deacclimation and how they may be impacted by climate change.

Quantitative and qualitative changes in carbohydrates associated with spring deacclimation in contrasting Hydrangea species

Cold deacclimation and associated changes in soluble carbohydrates and water status of two Hydrangea species differing in susceptibility to frost injuries was followed under natural conditions. In fully cold hardy plants of H. macrophylla stem freezing tolerance fluctuated in parallel with changes in air temperature, while in a seasonal perspective increased temperatures caused a sigmoid deacclimation pattern in both H. macrophylla and H. paniculata. Timing of deacclimation was approximately synchronized in the two species, but H. paniculata, the hardier species based on mid-winter hardiness, deacclimated faster than H. macrophylla, indicating that deacclimation kinetics were not correlated with mid-winter hardiness. In both species concentrations of soluble sugars decreased during deacclimation and were highly correlated with stem cold hardiness and air temperatures. This suggests that sugar hydrolysis may be an important temperature-driven mechanism of deacclimation in Hydrangea. Accumulation patterns of specific carbohydrates differed between the two species, suggesting that they utilize different strategies to overcome cold. In H. paniculata, deacclimation was associated with an increase in stem water content, which occurred shortly before bud burst and hence may be a prerequisite for leafing out.

Dehydrins expression related to timing of bud burst in Norway spruce

Cold deacclimation and preparation to flushing likely requires rehydration of meristems. Therefore, water stress related genes, such as dehydrins (DHN), might play an important role in providing protection during winter dormancy, deacclimation and bud burst timing processes. Here we report the sequence analysis of several Norway spruce DHN identified in late and early flushing suppressive subtraction hybridization cDNA libraries and in our Norway spruce EST database. We obtained 15 cDNAs, representing eight genes from three distinct types of DHN, and studied differential expression of these genes before and during bud burst in spring, using qRT-PCR. We found the visible reduction in transcript level of most DHN towards the bud burst, supported by a significant down-regulation of the DHN in needles during experimental induction of bud burst applied at three time points during autumn in Norway spruce grafts. For most of the DHN transcripts, their expression levels in late-flushing spruces were significantly higher than in the early flushing ones at the same calendar dates but were remarkably similar at the same bud developmental stage. From our results we may conclude that the difference between the early and the late families is in timing of the molecular processes leading to bud burst due to differences in their response to the increasing temperature in the spring. They are induced much earlier in the early flushing families.

Effects of temperature and nutrient availability on plasma membrane lipid composition in Scots pine roots during growth initiation.

We studied the effects of root zone temperature (RZT) and nutrient availability on free sterols and phospholipids in the plasma membrane (PM) and on PM-ATPase activity in roots of 1-year-old Scots pine (Pinus sylvestris L.) seedlings during growth initiation in the spring. Seedlings were grown for 6 weeks in hydroponic cultures with low (0.5 mM N; LN) or high (3 mM N; HN) nutrient availability. The root zone was subjected to slow warming (SW) and fast warming (FW) treatments while maintaining similar air temperatures in both treatments. Decreases in the amount of phospholipids and in the phospholipid/free sterol ratio, an increase in the degree of saturation of phospholipid fatty acids and changes in free sterol composition were observed during root growth initiation. Changes in lipid composition of the PM associated with the cold deacclimation process were detected at RZTs above 9 degrees C. Nutrient availability affected the lipid composition of the PM only when RZT was increased slowly. When RZT increased from 4 to 6 degrees C in the SW treatment, the degree of saturation of phospholipid fatty acids decreased, especially in HN seedlings. The sitosterol/stigmasterol ratio remained higher in HN seedlings than in LN seedlings. After an RZT of 9 degrees C had been reached in the SW treatment, HN caused increases in the saturation of phospholipid fatty acids and root PM-ATPase activity, and a decrease in the phospholipid/free sterol ratio. Possible effects of changes in PM lipid composition on root growth and PM-ATPase activity are discussed.

ABA and gibberellin-like substances during prehardening, cold acclimation, de- and reacclimation of oilseed rape

Previously published results showed that high relative reduction state of PSII (PSII excitation pressure) during both early seedling growth (prehardening) as well as cold deacclimation caused significant changes in growth pattern. The differences in elongation growth rate were related to the cold acclimation of photosynthetic apparatus and to frost resistance. To study changes in the hormonal balance connected with alterations in elongation growth rate observed during prehardening and deacclimation under different PSII excitation pressure (modulated by day-temperatures), endogenous concentration of ABA, GA3 and GA-like substances (GAs) were analysed. Analyses were also performed during cold acclimation and reacclimation of plants characterized by different elongation growth rate triggered by prehardening or deacclimation under different day-temperatures. Growth under high PSII excitation pressure (prehardening) resulted in a significant increase in ABA and a considerable decrease in GAs contents. On the other hand, different ABA content played almost no role in controlling growth rate during cold deacclimation and subsequent reacclimation, when the induction of elongation growth was connected with the changes in concentration of GAs including GA3. The possible role of ABA and GAs in controlling prehardening, cold acclimation and deacclimation is discussed.

Identification of a Gene for Putative myo-Inositol Oxygenase That Is Specifically Induced by Cold Deacclimation Treatment in Arabidopsis thaliana

Identification of a Gene for Putative myo-Inositol Oxygenase That Is Specifically Induced by Cold Deacclimation Treatment in Arabidopsis thaliana

Regulation of frost resistance during cold de-acclimation and re-acclimation in oilseed rape. A possible role of PSII redox state.

A possible role of photosynthetic apparatus during cold de-acclimation was studied in oilseed rape (Brassica napus var. oleifera). Plants of spring (Star) and winter (Górczañski) cultivars were cold acclimated at + 5 degrees C, and de-acclimated during 4 weeks at combinations of + 12 and + 20 degrees C operating in the light or/and dark, with a 12-h photoperiod. Evidence is presented that the photosynthetic apparatus may be involved in temperature perception during de-acclimation. De-acclimation was faster under a 20/12 degrees C (day/night) treatment than under the reverse 12/20 degrees C (day/night). De-acclimation rate was constant when the day temperature was constant, irrespective of the night temperature both under cold day temperature regimes (12/20, 12/12 degrees C (day/night) and warm-day treatments (20/12, 20/20 degrees C (day/night). The fast decrease in frost resistance observed under warm-day de-acclimation was always accompanied by an acceleration of elongation growth. In the spring cultivar, elongation growth increased starting from the second week of de-acclimation, regardless of temperature conditions. Once elongation growth had commenced during de-acclimation, it continued throughout the period necessary for re-acclimation to low temperature. Re-acclimation to the initial freezing tolerance level was only possible when plant elongation was reduced. In addition re-acclimation of the photosynthetic apparatus to low temperature was impossible in fast growing plants. A possible relationship between PSII, growth rate and frost resistance during cold acclimation and de-acclimation is discussed.

The Pattern of Changes in Photosynthetic Apparatus in Response to Cold Acclimation and De-acclimation in Two Contrasting Cultivars of Oilseed Rape

In spring and winter cultivars of oilseed rape (Brassica napus var. oleifera), acclimation of photosynthetic apparatus to cold was connected with the increase in activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and sucrose-phosphate synthase (SPS). Conversely, cold de-acclimation entailed the decline of RuBPCO and SPS activities. The rate of this photosynthetic de-acclimation might depend on day temperature. On the other hand, temperature rise during de-acclimation (identical during the day and night) resulted in the improvement of photosynthetic activity measured by means of chlorophyll fluorescence. An increase in SPS activity (and even transitory increase in RuBPCO activity) was observed when the elongation growth rate (EGR) accelerated during de-acclimation. Throughout re-acclimation, plants with high EGR were unable to maintain or recover higher photosynthetic capacity, despite the fact that SPS activity remained high or even increased during re-acclimation.

Regulation of energy balance in Zucker fatty rats and lean rats during cold acclimation and deacclimation

Regulation of energy balance in Zucker fatty rats and lean rats during cold acclimation and deacclimation

Variability in the Rate of Cold Acclimation and Deacclimation among Tuber-bearing Solanum (Potato) Species

Two major components of frost resistance are freezing tolerance in the nonacclimated state (growing in normal condition) and capacity to cold acclimate (increase in freezing tolerance upon exposure to chilling temperatures). In addition to these two major components, numerous factors contribute to frost survival. Although the rate of cold acclimation and deacclimation have been recognized as important factors contributing to frost survival, very little information about them is available. Our objective was to determine if there is variability in the rate of cold acclimation and deacclimation among tuber-bearing wild potato species: S. acaule Bitter, S. commersonii Dunal, S. megistacrolobum Bitter, S. multidissectum Hawkes, S. polytrichon Rydb., S. sanctae-rosae Hawkes, and S. megistacrolobum subsp. toralapanum (Cárdenas & Hawkes) Giannattasio&Spooner. Relative freezing tolerance of these species was measured after 0, 3, 6, 9 and 12 days of cold acclimation and after 12 and 24 hours deacclimation. Our results showed there were differences in the rates of cold acclimation and deacclimation among these species. With respect to the rate of acclimation we found these species can be divided into four groups: (i) early; (ii) late acclimators; (iii) progressive acclimators, and (iv) nonacclimators. Likewise, a wide range of cold deacclimation behavior was found. Some species showed as low a loss of 20% of their freezing tolerance, others showed as much as >60% loss after 12 hours of deacclimation. Significant deacclimation was observed in all cold acclimating species after 1 day. These results demonstrate that the rates of cold acclimation and deacclimation were not necessarily related to the cold acclimation capacity of a species. Rapid acclimation in response to low temperatures preceding a frost episode and slow deacclimation in response to unseasonably warm daytime temperatures could be advantageous for plants to survive frost events. Thus, in addition to nonacclimated freezing tolerance and acclimation capacity, it would be very desirable to be able to select for rapid acclimation and slow deacclimation abilities. Results demonstrate that variability for these two traits exists in Solanum L. (potato) species.

In vitro and in vivo induction of brown adipocyte uncoupling protein (thermogenin) by retinoic acid

The effects of retinoic acid (RA) isomers (all-trans-RA and 9-cis-RA) on the appearance of uncoupling protein (UCP; thermogenin), the only unequivocal molecular marker of the brown adipocyte differentiated phenotype, have been investigated in primary cultures of brown adipocytes, in the brown adipocyte cell line HIB 1B and directly in intact mice. The results obtained with cultured cells indicate that retinoids function as inducers of the appearance of UCP and, at the same time, partially inhibit brown adipocyte cell proliferation. The two RA isomers displayed similar effectiveness as UCP inducers, their effect being comparable with that triggered by noradrenaline, so far considered to be the main modulator of UCP gene expression. The effectiveness of retinoids as UCP inducers was dependent on the stage of brown adipocyte differentiation, being maximal in confluent primary cells and in the medium-late differentiation stage of HIB 1B cells. Corroborating the results obtained in vitro, we show that administration of all-trans-RA or 9-cis-RA to mice leads to an increase in their brown adipose tissue specific UCP content. 9-cis-RA treatment also prevented the loss of UCP on cold deacclimation. To our knowledge, this is the first report of a stimulatory effect of retinoid compounds on UCP induction in vivo.

Variability in the Speed of Cold Deacclimation among Tuber-bearing Wild Potato Species

Frost injury limits the cultivation of potatoes in many regions around the world. We are currently studying the factors that contribute to frost survival in potato in an attempt to improve its frost tolerance. Wild potato species have been distinguished for their high degree of non-acclimated frost tolerance (growing under normal conditions) and their high cold acclimation capacity (able to increase frost tolerance upon exposure to cold). Cold acclimation can be reversed upon exposure to warm temperatures (deacclimation). The ability to gain freezing tolerance rapidly in response to low temperatures as well as not being able to deacclimate rapidly in response to warm daytime temperatures would be advantageous for a plant against spring or fall freezes. Last year we presented evidence for the variability in the speed of cold acclimation among 7 wild tuber-bearing potato species (S. acaule, S. commersonii, S. megistacrolobum, S. multidissectum, S. polytrichon, S. sanctae-rosae and S. toralapanum). The same set of species was used for the present study to find out if there is also variability for the speed of deacclimation. Relative freezing tolerance of these species was measured before and after cold acclimation as well as after one day of deacclimation (exposure to warm temperatures). Our results suggest that there are differences in the speed of deacclimation among these species. We found that while some species lost near a half of their hardiness, others lost only a third or less of their hardiness after one day of deacclimation.

Relationships among cold hardiness, root growth potential and bud dormancy in three conifers.

Greenhouse-cultured, container-grown ponderosa pine (Pinus ponderosa var. scopulorum Engelm.), interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and Engelmann spruce (Picea engelmannii (Parry) Engelm.) were cold acclimated and deacclimated in growth chambers over 19 weeks. Stem cold hardiness, total new root length at 14 days and days to bud break were measured weekly. Relationships among cold hardiness, root growth potential (RGP) and bud dormancy suggest that cold hardiness, which can be measured quickly, could provide a useful basis for estimating the two other parameters. During cold acclimation, there was a lag period in which stem cold hardiness remained at -15 degrees C and RGP was at a minimum, in all three species. Douglas-fir and Engelmann spruce buds remained fully dormant during this lag period. Ponderosa pine buds had no chilling requirement for the loss of dormancy, and reached quiescence during the lag period. Immediately following the lag period, as stem cold hardiness progressed to -22 degrees C, RGP increased to a high plateau in all three species, and Douglas-fir and Engelmann spruce buds approached quiescence. Cold deacclimation and bud development began immediately on exposure to warm, long days, but RGP remained high until stem cold hardiness returned to approximately -15 degrees C. At bud break, cold hardiness and RGP were at the minimum.

Shivering and nonshivering thermogenesis in exercised cold-deacclimated rats.

Norepinephrine (NE)-induced increase in oxygen consumption (VO2) and colonic temperature (Tc) was greater in cold-acclimated rats housed at 4 degrees C for 4 weeks (CA) than warm-acclimated controls housed at 24 degrees C for 4 weeks (WA). On the other hand, shivering activity measured at 4 degrees C was less in CA than in WA, while propranolol administration eliminated the difference between these two groups by enhancing shivering in CA. Wet weight and protein content of interscapular brown adipose tissue (IBAT) were greater in CA than in WA. Following cold acclimation, CA were deacclimated at 24 degrees C for 5 weeks. During deacclimation, half of this latter group were forced to run (15 m.min-1 for 1 h) every day (CD-T) while the remaining rats remained sedentary (CD-S). Shivering activity assessed at 4 degrees C 4 weeks after commencing cold deacclimation was significantly less in CD-T than in CD-S and the difference disappeared following propranolol injection. VO2 and Tc responses to NE injection measured 1, 2 and 5 weeks after commencing cold deacclimation did not differ between CD-S and CD-T. Although IBAT weight was lighter in CD-T than in CD-S, its total protein content was not different between the latter two groups of rats. These results suggest that a greater degree of NE-independent nonshivering thermogenesis (NST) is retained in rats that are exercised during the process of deacclimation as compared with animals that are sedentary. This difference in NST would not seem to be directly related to BAT thermogenic capacity.

Effects of Temperature on Cold Acclimation and Deacclimation in Flower Buds of Evergreen Azaleas

Effects of Temperature on Cold Acclimation and Deacclimation in Flower Buds of Evergreen Azaleas

Effect of Cold Deacclimation on Delayed Fluorescence of Spruce Needles

Delayed fluorescence of chlorophyll in the time range of 3–18 ms was studied in intact spruce needles. The temperature dependence of delayed fluorescence was measured during cold deacclimation and after artificial dehardening of the frostresistant P. abies and the frost-susceptible P. schrenkiana. After dehardening of the needles as well as during release of deep rest there is an increase in the intensity of delayed fluorescence emission accompanied by simultaneous lowering of the temperature maximum of delayed fluorescence. Both of the responses are larger in the frost-susceptible P. schrenkiana responds to dehardening more strongly. The relation between cold deacclimation of the spruce needles and photosynthetic electron transport is discussed.

Supercooling Ability, Water Content and Hardiness of Rhododendron Flower Buds during Cold Acclimation and Deacclimation

Supercooling Ability, Water Content and Hardiness of Rhododendron Flower Buds during Cold Acclimation and Deacclimation

Some Postulated Relationships among Autumn Phenomena in Woody Plants

MOST research on winter hardiness (cold acclimation) of plants has been concerned with changes in amounts of organic compounds such as sugars, amino-acids and proteins. These autumnal alterations in organic constituents of the cell can only be brought about by changes in enzymes. The question as to what initial factor causes this change in the metabolism is still not solved. It is tempting to think of a hormone action which could influence a great many enzyme systems1, especially since cold acclimation and de-acclimation are closely associated with the growth-regulator controlled phenomenon of growth cessation in autumn, and growth resumption in spring. Recently, Levitt2 has suggested that protein and glutathione sulphydryls bear a direct relationship to the state of winter hardiness of plants. Sulphydryl groups in cells are essential for the three-dimensional structure of cell proteins3 and for cell growth4. Glutathione is also an essential part of the ascorbic acid oxidase system which is involved in growth processes, that is, ascorbic acid oxidizing capacity is low in growing plants and high in dormant plants. Marre and Arrigoni5 presented evidence that auxins inhibited the ascorbic acid oxidase and thereby increased the ratio of reduced to oxidized glutathione. A postulated relationship between ascorbic acid oxidase and glutathione can be represented as follows: AH2, metabolic substrate; G-S-S-G, oxidized glutathione; GSH, reduced glutathione; AA, ascorbic acid; DH,A dehydroascorbic acid.