Weeks Of Chilling Research Articles

Stable Isotope Labelling Reveals Water and Carbon Fluxes in Temperate Tree Saplings Before Budbreak.

Despite considerable experimental effort, the physiological mechanisms governing temperate tree species' water and carbon dynamics before the onset of the growing period remain poorly understood. We applied 2H-enriched water during winter dormancy to the soil of four potted European tree species. After 8 weeks of chilling, hydrogen isotopes in stem, twig and bud water were measured six times during 2 consecutive weeks of forcing conditions (Experiment 1). Additionally, we pulse-labelled above-ground plant tissues using 2H-enriched water vapour and 13C-enriched CO2 7 days after exposure to forcing conditions to trace atmospheric water and carbon uptake (Experiment 2). Experiment 1 revealed soil water incorporation into the above-ground organs of all species during the chilling phase and significant species-specific differences in water allocation during the forcing conditions, which we attributed to differences in structural traits. Experiment 2 illustrated water vapour incorporation into all above-ground tissue of all species. However, the incorporation of carbon was found for evergreen saplings only. Our results suggest that temperate trees take up and reallocate soil water and absorb atmospheric water to maintain sufficient above-ground tissue hydration during winter. Therefore, our findings provide new insights into the water allocation dynamics of temperate trees during early spring.

Daylength effects on black spruce bud dormancy release change during endo- and ecodormancy

The effects of daylength on bud dormancy release varied throughout the dormant period in black spruce (Picea mariana (Mill.) B.S.P.) seedlings. In phase one of this trial, seedlings exposed to 8 h photoperiods to induce terminal buds were then intermittently transferred to 12, 16, 18 or 24 h photoperiods to determine dormancy status, evaluated by observing rates of terminal budburst. Buds were in a state of endodormancy initially after short-day induction, as indicated by their inability to quickly break bud when placed in longer daylengths. The time required for budburst decreased as time after bud initiation increased. Time to terminal budburst also decreased linearly with longer photoperiods. In phase two of the investigation, beginning 9 weeks after terminal bud initiation, seedlings began receiving chilling at +5°C to promote the transition from endo- to ecodormancy. During chilling, groups of seedlings were periodically removed from the cold and placed into warm temperatures at 8, 12, 16, 18 or 24 h photoperiods to observe the rate of budburst. Time to budburst in an 8 h photoperiod decreased logarithmically with the duration of chilling, decreasing more rapidly over the first four weeks of chilling and thereafter more slowly. Photoperiod always affected the rates of budburst: with eight weeks of chilling, longer photoperiods resulted in faster rates of budburst; in contrast, after 16 weeks of chilling, budburst was faster in shorter photoperiods. These results are of practical significance in tree nurseries where controlling bud dormancy release is important. In addition, this trial provides empirical observations of bud dormancy release that contribute to the understanding of environmental control of this aspect of the tree developmental cycle, which may affect tree phenology as the climate changes.

Average daily temperature controls floral bud formation rate, callose deposition and flower development of Hydrangea macrophylla ‘Early Blue’

ABSTRACT Hydrangea macrophylla ‘Early Blue’ was exposed to six different day (DT) and night (NT) and average daily temperatures (ADT) during flower bud formation (DT/NT°C: 12/12, 17/12, 17/17, 22/12, 22/17, 22/22). The aim was to evaluate the effect of ADT and DT/NT on the rate of bud formation and forcing time after a period of chilling. Furthermore, the role of callose in dormancy induction and release during cold storage was investigated. ADT ≤ 17°C accelerated flower bud formation irrespective of DT and NT compared to an ADT > 17°C. Floral buds developed at ADT 17°C contained significantly lower level of callose compared to buds from the higher ADT regimes (ADT >17°C). After 6 weeks of chilling (10°C) the callose level was decreased to a similar level irrespective of the DT/NT regime during floral bud formation and/or floral stage at the start of the chilling treatment. We conclude that callose may play an important role in the dormancy release of H. macrophylla. However, floral buds do not have to be fully developed to remove the callose in response to chilling and no clear relationship was found between the levels of callose after chilling and forcing time.

Mycosis Fungoides in 2 Pediatric Patients with Atopic Dermatitis

A 16-year-old girl with a lifetime history of atopic dermatitis (AD) and multiple food allergies presented with complaints of worsening dermatitis over several months in the setting of 2 weeks of chills, total body redness with mild pruritus, and hair shedding. Physical examination demonstrated erythroderma, scaly plaques, overlying firm skin-colored papules (Figures 1 and 2), thinning hair of the scalp and eyebrows, and cervical and inguinal lymphadenopathy. Skin biopsy was pursued given unusual presentation, including pruritus that was less than expected for AD.

3009 Importance of Prompt Diagnosing and Treatment of Type 1 Autoimmune Pancreatitis

INTRODUCTION: Type 1 Autoimmune Pancreatitis (AIP) is a rare cause of chronic pancreatitis that accounts for only 2% of chronic pancreatitis cases. Mainly presenting in males between ages of 50-70. This is IgG4 related disease. It commonly presents with abdominal pain, jaundice, and weight loss. AIP is primarily diagnosed clinically and later confirmed through radiological and serological studies. Because pancreatic cancer presents similarly but differentiates in treatment, it is important to distinguish between the two. CASE DESCRIPTION/METHODS: A 72-year-old male with a PMH of chronic pancreatitis presented for evaluation of loss of appetite, fatigue and 100 lb weight loss over the course of 7 weeks. He also admitted to two weeks of chills and diaphoresis, and denied abdominal pain, diarrhea or constipation. On admission, there was no jaundice present and vitals were unremarkable, except for a temperature of 102 F. Patient's labs were within normal limits, except for sodium 129, ESR 85, total bilirubin 1.3, AST 101, ALT 79, and ALP 364. CT showed the pancreas heterogeneous, an ill-defined mass, consistent with pancreatic adenocarcinoma. Furthermore it showed hepatomegaly with numerous low-density lesions consistent with hepatic metastases. Biopsy of the pancreatic mass displayed a storiform fibrosis pattern with an elevated IgG4 of 3.8 g/L, suggesting Type 1 AIP. Liver biopsy was negative for malignant cells. Patient was diagnosed with AIP and was discharged on a steroid regimen. DISCUSSION: Type 1 AIP is defined as a fibro-inflammatory process that often includes elevated IgG4 levels. Imaging can also reveal irregular narrowing of the pancreatic duct with diffuse or focal enlargement of the pancreas. It is important to distinguish between AIP and pancreatic cancer due to the different treatments and prognosis. A study found AIP to account for 27% of Whipple resections performed for suspected pancreatic adenocarcinoma. AIP has a benign clinical course and is highly responsive to steroids. An elevated IgG4 together with imaging studies are the most sensitive and specific finding; an IgG4 value of >2.8 g/L distinguishes AIP from other inflammatory or malignant conditions. Finally, the prompt diagnosis of AIP is important for appropriate follow up. Studies have demonstrated an increased risk of developing cancer of the stomach, prostate, colon and bile duct post diagnosis of AIP. A retrospective study of 108 patients with AIP, 18 cancers were found in 15 patients in the median follow-up period of 3.3 years.

Temporal Aspects of Vernalization and Flowering in Long-day Storage Onion

Vernalization is an important step for floral initiation in onion (Allium cepa), but our understanding of the minimum vernalization time for long-day storage onions to gain floral competence is limited. A series of time course experiments were conducted over 4 years to determine the effects of vernalization time on sprouting, scape emergence, and flowering in ‘Cortland’, ‘Sherman’, and CUDH2107. We found an endodormancy period is present in the bulbs of these cultivars that lasts for 8 to 10 weeks. In addition, these three accessions achieve optimum uniform scape emergence after chilling for 14 weeks at 10 °C. On average, when bulbs were chilled for 14 weeks, it took 96.8 ± 15.6 days from planting to flowering in all accessions evaluated. As storage duration under vernalizing temperatures increases, the time to sprouting, scape emergence, and flowering decrease. Furthermore, the variance in time from sprouting to scape emergence was greatly reduced between 10 and 12 weeks of storage for ‘Cortland’ and CUDH2107, and between 12 and 14 weeks for ‘Sherman’. After 10 weeks of chilling, each additional week of storage resulted in an average decrease in time to flowering of 4.1%. We also observed large percentages of bulbs flowering without receiving any vernalization. This observation supports our finding that the relationship between vernalization and flowering in long-day storage onion is facultative rather than obligate. These findings help define the relationship between dormancy, vernalization, and flowering in long-day storage onion.

Breaking seed dormancy in European rowan seeds and its implications for regeneration

The effects of the presence of a medium, seed moisture content, warm and chilling treatments on the germination response of European rowan (Sorbus aucuparia L.) seeds of Irish origin were investigated with the aim of reducing precocious (or premature) germination and maximising germination after pretreatment. After adjusting seed moisture content, seeds of two lots were subjected to warm treatment for 0–6 weeks followed by 0–50 weeks of chilling. The seeds then were allowed to germinate at a constant 15 °C with 8 h lighting per day or 20 (dark)/30 °C (light). Some seeds were treated in the fully imbibed (FI) state in a medium (standard operational treatment). Seed lot effects were evident, but treatment effects were consistent in each lot. Warm treatment greatly increased germination and reduced precocious germination. The presence of a medium was not required to achieve high germination and seed moisture content close to the FI state was needed to maximise germination. Climate change may reduce the ability of this species to regenerate naturally, favouring other species that require less chilling.

Understanding chilling responses in Arabidopsis seeds and their contribution to life history

Winter chilling is of central importance in the phenology of temperate annual and perennial plants. Chilling accelerates flowering through the process of vernalization and breaks both bud and seed dormancy, permitting the onset of growth in the spring. The quantitative effects of chilling in floral promotion in winter annual Arabidopsis accessions are well-documented, but very little is known about the basic physiology underlying summer annual responses to winter chilling, which acts on seeds within the soil seed bank. Here, we analyse the response of wild accessions to extended chilling in seeds, and explore the interaction between seed-maturation temperature and chilling responses. We show that two weeks of chilling induces secondary dormancy, and that this time period is not dependent on seed-maturation temperature. In addition, we found that seeds for most accessions set under simulated summer conditions in the laboratory are unable to overwinter in the soil seed bank, as they germinate without light during extended chilling treatments. This shows that these seeds are committed to re-establishment in the same growing season. Understanding how winter chilling affects the timing of Arabidopsis phenology will enable us to explore the genetics behind adaptation to changing climates, and inform rational approaches to breeding crops with improved performance under new climate scenarios and develop a systems ecology of Arabidopsis.

Effect of long-phase stratification treatments on seed germination in ash

Ash (Fraxinus excelsior L.) seeds require warm treatment followed by cold treatment to release dormancy and this is most effective if carried out in a medium. The objective of this study was to determine if long periods of warm treatment would enhance germination at 15 (8-h light)/5°C (dark) and 15°C (same lighting conditions) in ash seeds of north-western European origin. Ash seeds were fully imbibed (57% moisture content (MC)) or adjusted to 45% MC either in a medium or without a medium for 10–30 weeks of warm treatment, followed by 10, 20 or 30 weeks of chilling. Germination increased at both germination temperature regimes as the duration of warm treatment increased up to 18 (with medium) or 20–30 (without medium) weeks, well after the embryo had completed development (14 weeks). The response to 20 or 30 weeks of chilling was better than that of 10 weeks of chilling, but the impact of chilling was smaller than that of warm treatment. Seed MC did not significantly affect germination, but it reduced mould growth. A long warm treatment (followed by cold treatment) without a medium is the recommended treatment for ash seeds.

Contents of polyamines during vernalization in wheat and the effect of zearalenone

The contents of endogenous free and conjugated polyamines, putrescine (Put) and spermidine (Spd), were determined during 9 week of vernalization (at 5 °C) in winter wheat seedlings cultivated on Murashige and Skoog media without (MS0) and with 2 mg dm−3 zearalenone (MSZEN). At the 4th week of chilling treatment, which is sufficient to induce generative development in 30 % of plants, the marked increase in free and conjugated forms of Put and free Spd were observed. The presence of ZEN in medium significantly accelerated the vernalization. About 20 % of plants treated with ZEN flowered already after 2 weeks and 40 % after 3 weeks of chilling. Significantly higher content of free Put was determined in roots grown on MSZEN compared with MS0 during the first 5 weeks of vernalization with maximum at the 4th week. After germination, a marked decrease in free Spd content was observed both in plants grown on MS0 and MSZEN. Application of ZEN significantly slowed down the Spd decline in leaves and roots during the first and second week of vernalization. The content of Spd and its conjugates decreased in vernalized plants after 1 week of cultivation at 20 °C.

Recovery of maize ( Zea mays L.) inbreds and hybrids from chilling stress of various duration: Photosynthesis and antioxidant enzymes

The differences between two maize (Zea mays L.) inbred lines and their F1 hybrids in their response to chilling periods of various duration (1, 2, 3 or 4 weeks) and subsequent return to optimum temperatures were analysed by the measurement of the photosystem (PS) 1 and 2 activity, the photosynthetic pigments' content and the activity of antioxidant enzymes. The PS2 activity and the chlorophyll content decreased in plants subjected to 3 or 4 weeks of chilling, but not in those subjected to 1 or 2 weeks of chilling. This decrease was more pronounced in inbreds compared to their hybrids. The activity of superoxide dismutase did not much change with the increasing length of chilling period in the inbreds but decreased in the hybrids, the glutathione reductase activity increased in both types of genotypes but more in the inbred lines, while for ascorbate peroxidase and catalase the changes in parents-hybrids relationship did not show any specific trend. The PS1 activity and the carotenoids' content was not much affected.

Phytic acid mobilization is an early response to chilling of the embryonic axes from dormant oilseed of hazel (Corylus avellana)

Dormancy of hazel (Corylus avellana L.) seeds is alleviated by a chilling treatment during which cytological, hormonal, and biochemical changes occur. Phytic acid and phosphate mobilization have been examined during this treatment. Phytic acid accounted for 0.7% and up to 3.2% of dry weight in axiferous and cotyledonary tissue, respectively. Phytic acid levels in embryonic axes were reduced by 60% within the first 3 weeks of chilling, with little subsequent change, in contrast to warm-imbibed tissue where levels did not change significantly. In cotyledons, phytic acid was mobilized to a lesser extent. Phosphate levels expressed on a fresh weight basis remained almost unaltered suggesting either the operation of a homeostatic mechanism for intracellular concentration or rapid utilization due to active metabolism. Phytase activity increased during stratification in both axiferous and cotyledonary tissue. The initial rise observed was associated with dormancy alleviation, since it occurred before the realization of full germination potential by the seeds and not in warm-imbibed tissue. Protein bodies were isolated from hazel seeds by non-aqueous density gradients. Phytase activity was closely associated with the purified organelles, where phytic acid was located by light microscopy. Overall, these findings suggest that phytic acid mobilization by phytase and previously described processes associated with protein bodies, such as considerable proteolysis, are early participants in the plethora of events leading to seed dormancy relief and germination in hazel.

Chilling Duration, Container Size and Photoperiod Influence Flowering of Aruncus `Misty Lace'

Aruncus `Misty Lace is a new hybrid selection between Aruncus dioicus and A. aethusifolius. The plants outstanding characteristics include heat tolerance, dwarf stature, and delicate, plume-like flowers. The objectives of this study were to evaluate the effect of different production parameters (chilling duration, container size, and photoperiod) on flowering in this new genotype Tissue cultured plantlets of Aruncus `Misty Lace' were transplanted to 72- or 36-cell trays and to 10-cm pots. Transplanted materials remained on the greenhouse bench until roots were visible in the soil plug, then placed in a cooler at 2-4 °C for 0 (control), 4, 6, 8, 10 and 12 weeks of chilling. Upon removal, plants were placed in a greenhouse in 10-cm containers under long or short day photoperiods until flowering, or until the experiment was terminated. Plants required less time on the bench to flower as cooling time increased, regardless of container size. Plants flowered earlier under long days than short days, but photoperiod was less of a factor in the control of flowering than cooling duration. Death of plants was greatest in the 72-plug cells and least in 10-cm pots. Plants without well established root growth sustained significant losses, regardless of container size.

Effect of Chilling Duration on Growth of Hosta plantaginea and 11 Related Cultivars

Abstract Hosta plantaginea and 11 selections with H. plantaginea parentage were chilled at 4C (39F) for 0, 1, 2, 3, or 4 weeks to determine the effect of chilling duration on subsequent plant growth. At 6 and 12 weeks after chilling treatment (WAT), response to chilling duration was selection dependent with three trends evident. At 6 WAT, eight of the 12 selections showed a decrease in new leaf formation with one or two weeks of chilling, but an increase in new leaf formation with additional chilling. In three of the 12 selections, new leaf formation increased linearly with increased chilling. New leaf formation of H. plantaginea ‘Grandiflora’ was not affected by chilling duration at 6 or 12 WAT. At 12 WAT, growth response of four of the 12 selections changed quadratically with increased chilling, similar to the response at 6 WAT, while leaf formation in seven of the 12 selections increased linearly with increasing chilling duration. At 18 WAT, leaf counts increased linearly in all H. plantaginea selections with increasing chilling duration, demonstrating increased vigor. All selections showed increases in new leaf formation over the 18-week period following chilling, demonstrating that chilling, though beneficial, was not required, and in the short-term, the response to chilling was selection dependent.

Effects of Chilling Duration on Time to Shoot Emergence and Subsequent Growth of Hosta

Abstract Eight hosta species or cultivars, Hosta plantaginea, H. ventricosa ‘Aureo Marginata’, H. ‘Tokudama’, H. ‘Francee’, H. ‘Sum and Substance’, H. ‘Fragrant Bouquet’, H. ‘Frances Williams’, and H. sieboldiana ‘Elegans’, were chilled in a walk-in cooler in two-week increments from 2 to 10 weeks at 4C (39F), prior to forcing in a heated greenhouse. More than 80% of all cultivars in all treatments emerged, except for H. ‘Tokudama’. For all cultivars tested, days to shoot emergence and days to first leaf unfurled decreased quadratically as chilling duration increased. Most rapid decreases occurred between 0 and 6 weeks of chilling. In the absence of chilling, H. plantaginea was the first cultivar to emerge, between 34 and 79 days before other cultivars. H. plantaginea was followed by H. ventricosa ‘Aureo Marginata’, H. ‘Sum and Substance’, and H. ‘Fragrant Bouquet’, all of which emerged before H. ‘Frances Williams’. Leaf area index, an indicator of plant vigor, increased linearly as chilling duration increased. Shoot dry weight increased in H. ‘Fragrant Bouquet’, H. ‘ Frances Williams’ and H. ‘Francee’, decreased slightly in H. plantaginea, and did not change in H. ventricosa ‘Aureo Marginata’, H. ‘Tokudama’, H. ‘Sum and Substance’, or H. sieboldiana ‘Elegans’ as chilling duration increased. This study indicates that there is no absolute chilling requirement for shoot emergence or subsequent growth of hosta tested. All cultivars benefited from chilling with quicker shoot emergence and fewer days to first leaf unfurled, with the greatest benefits occurring between 0 and 6 weeks. However, the benefits of chilling, as exemplified by growth and vigor, varied widely among species and cultivars.

Breakage of Pseudotsuga menziesii seed dormancy by cold treatment as related to changes in seed ABA sensitivity and ABA levels.

The main aims of the present work were to investigate whether a chilling treatment which breaks dormancy of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) seeds induces changes in the sensitivity of seeds to exogenous ABA or in ABA levels in the embryo and the megagametophyte, and whether these changes are related to the breaking of dormancy. Dormant seeds germinated very slowly within a narrow range of temperatures (20-30 degrees C), the thermal optimum being approximately 25 degrees C. The seeds were also very sensitive to oxygen deprivation. Treatment of dormant seeds at 5 degrees C improved further germination, and resulted in a widening of the temperature range within which germination occurred and in better germination in low oxygen concentrations. In dry dormant seeds the embryo contained about one-third of the ABA in the megagametophyte. ABA content of both organs increased during the first 4 weeks of chilling. It then decreased sharply in the megagametophyte to the level in the embryo after 7-15 weeks of chilling. At 15 degrees C, a temperature at which dormancy was expressed, the ABA level increased in the embryo and the megagametophyte of dormant unchilled seeds whereas it decreased in the organs of chilled seeds. The longer the chilling treatment, the faster the decrease in ABA after the transfer of seeds from 5 degrees C to higher temperatures, and the decrease was faster at 25 than at 15 degrees C. These results suggest that the breaking of dormancy by cold was associated with a lower capacity of ABA biosynthesis and/or a higher ABA catabolism in the seeds subsequently placed at 15 or 25 degrees C. Moreover, the chilling treatment resulted in a progressive decrease in the sensitivity of seeds to exogenous ABA. However, seeds remained more sensitive to ABA at 15 than at 25 degrees C. The possible involvement of ABA synthesis and of responsiveness of seeds to ABA in the breaking of dormancy by cold treatment is discussed.

苗齢，苗の高温および低温遭遇，並びに低温遭遇後の生育温度がトルコギキョウの抽だいに及ぼす影響

1. 'あすかの桜'と'あすかの朝'を供試し, 播種直後から30/25℃(昼/夜温)で0∿6週間育苗して苗齢を異にした苗を, 11℃で3週間低温処理し, その後30/25℃, 27.5/17.5および22.5/12.5℃で栽培したところ, 苗の抽だい株率は, 生育温度が30/25℃では13∿88%だったのに対し, 22.5/12.5℃では苗齢に関わらず100%抽だいした.3週間低温遭遇した苗に対し, 高温は抽だいを促進しなかったことから, 高温下におかれること(低温に遭遇しないこと)は直接, 形態的なロゼット化を誘導する要因と考えられる.2. 'あすかの粧'と'都桃'を供試し, 播種直後から35/25℃で0∿6週間育苗した苗を, 11℃で5週間低温処理し, その後35/25℃∿25/15℃で栽培したところ, 低温処理終了時の苗齢が'あすかの粧'では1.1節, '都桃'では2.3節以上に達していた場合に限ってすべての株が抽だいし, それ以下の苗齢では高温下で栽培するほどロゼット株率が高くなった.3. 'あずまの桜', 'あすかの桜'および'あすかの朝'を供試し, 播種直後から35/25℃で0∿14日間育苗した苗を, 11℃で1∿5週間低温処理し, その後35/25℃で栽培したところ, 3∿5週間の低温処理により, 苗齢に関わらずほとんどの株が抽だいした.同様に, 播種直後から4∿8週間高温下で育苗し, その後, 3∿6週間の低温処理を行ったところ, 5週間以上の低温処理により, すべての株が抽だいした.このことから, ロゼット性の弱いこれらの品種では, 一定の低温量を充足することが抽だいの条件であると考えられる.

Coinfection With Babesia microti and Borrelia burgdorferi in a Western Wisconsin Resident

A 68-year-old woman, who had not traveled outside of western Wisconsin, was hospitalized after 4 weeks of chills, fevers, myalgias, neuralgias in her right arm, and pain in the right upper quadrant of her abdomen. Physical examination revealed hepatosplenomegaly, and laboratory studies showed anemia, thrombocytopenia, increased aspartate transaminase level, and microscopic hematuria. Wright's stain of a blood smear revealed intraerythrocytic organisms consistent with Babesia species. A polymerase chain reaction of whole blood specimens along with an increased serologic titer confirmed the diagnosis of Babesia microti. Indirect immunofluorescent antibody serology and Western blot analysis revealed a simultaneous infection with Borrelia burgdorferi. Coinfection with B. microti and B. burgdorferi may occur in endemic areas where both organisms are carried by the same tick vector, Ixodes scapularis. The intensity and duration of illness seem to be greatest in patients with concurrent infection.

Dormancy-breakage in seeds of Douglas fir ( Pseudotsuga menziesii (Mirb.) Franco). Support for the hypothesis that LEA gene expression is essential for this process

Summary In Douglas fir seeds ( Pseudotsuga menziesii (Mirb.) Franco), dormancy-breakage is associated with quantitative and qualitative changes in gene expression. Specific examples of genes that are up-regulated during dormancy-breakage include those encoding LEA proteins (DF6, DF65 and DF77) (Jarvis et al., J. Plant Physiol. 147: 559–566, 1996). In particular, DF65, a dehydrin, was specifically expressed during stratification and DF6 and DF77 were significantly up-regulated. On examination of the tissue distribution of the LEA gene transcripts during chilling (which breaks dormancy) and warm-incubation, LEA transcripts were detected in both embryo and megagametophyte tissues. Expression of DF65 was lower, and the transcript appeared later, in the embryo than in the megagametophyte. With DF6 and DF77, transcripts reached maximal levels in the megagametophyte earlier than in the embryo. While de novo synthesis of ABA was important for the expression of dormancy, four weeks of chilling, only led to a 36% reduction in endogenous ABA and did not change its distribution between the embryo and megagametophyte, compared with warm-incubated seeds. However, following chilling, seeds showed a reduced sensitivity to applied ABA. To determine if there was a link between the expression pattern of LEA genes and the dormancy status of the seeds and/or abiotic stresses, seeds were treated with the plant growth regulators ABA and Me-JA, or subjected to osmotic, salt, and heat stresses. ABA treatment prevented germination of non dormant seeds, and did not induce expression of LEA genes. Me-JA stimulated dormant seeds to germinate and induced low level expression of all three LEA genes after 24 hours, but not after one week. Expression of all three LEA genes was detected in seeds which had been subjected to osmotic and salt stresses expression. However, under heat stress only DF6 and DF77 were expressed. The degree of induction by these treatments was much less than that induced by chilling. We conclude that the primary role of these gene products is connected with changes that occur during the cold, moist treatment that leads to dormancy-breakage in seeds.

Effect of Cold Storage on Bud Break, Root Regeneration and Shoot Extension of Douglas Fir, Paper Birch and Green Ash

Abstract Dormancy level, days to bud break, root regrowth and rate of shoot extension were determined for 18-in seedlings of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), paper birch (Betula papyrifera Marsh.) and green ash (Fraxinus pennsylvanica Marsh.) subjected to varying durations of cold storage. Douglas fir seedlings did not break bud unless exposed to at least 4 weeks of cold storage, but bud break was unaffected by further time in cold storage. The number of regenerated roots increased with time in cold storage until 12 weeks of chilling and decreased sharply thereafter. Days to bud break of paper birch and green ash decreased as chilling time accumulated. Full dormancy release and maximum root regeneration of paper birch coincided at 10 weeks of chilling. Green ash achieved full dormancy release after 14 weeks of cold storage. The number of roots regenerated increased with cold storage duration for green ash. Shoot extension rate of all species was little affected by chilling duration. Implications for transplanting are discussed.