Leaf habit influences nitrogen remobilization in Vaccinium species.

The effect of N supply on plant growth and leaf demography of a deciduous and an evergreen Ericaceae was studied in relation to their internal cycling of N. Mature ramets of Vaccinium myrtillus (deciduous) and Vaccinium vitis-idaea (evergreen) were established in sand culture for 1 year with an adequate supply of a balanced nutrient solution. During one growing season, the plants were given two levels of N supply enriched with 15N and eight sequential destructive harvests were taken. Recovery of unlabelled N in the new shoot was used to determine the remobilization of N from storage. Initially, growth was unaffected by N supply. After May, High N enhanced growth for both species but the nature of their growth response differed. For both species, new shoot biomass and leaf number increased but root biomass production was affected for V. myrtillus only. Whole plant biomass production was similar for both species under High N, but was greater for V. vitis-idaea under Low N. The amount of N remobilized to support new shoot growth was similar for the two species and was independent of N current supply. N was remobilized predominantly from previous year leaves for V. vitis-idaea and from previous year stems and roots for V. myrtillus. The contribution of remobilization to new shoot N was similar for the two species, but depended on N supply. Remobilization was faster in V. myrtillus, but lasted longer in V. vitis-idaea. The results are discussed in relation to species growth in N-poor environments, focusing on the extent to which species-differences in the dynamic of N remobilization and growth may explain their adaptation to constant and/or changeable N supply.     

Contrasting strategies for UV-B screening in sub-Arctic dwarf shrubs

The content and distribution of UV-absorbing phenolic compounds was investigated in leaves of three species of Vaccinium co-existing at a site in north Sweden. Vaccinium myrtillus L., Vaccinium vitis-idaea L., and Vaccinium uliginosum L. exhibit markedly different strategies, in terms of localization and content of leaf phenolics and in their responses to UV-B enhancement. Plants were exposed to either ambient radiation or to enhancement of UV-B corresponding to 15% (clear sky) depletion of stratospheric ozone for approximately 10 years prior to commencement of this study. Vaccinium myrtillus contained the highest concentration of methanol-extractable UV-B-absorbing compounds, which was elevated in plants exposed to enhanced UV-B. Fluorescence and confocal laser scanning microscopy showed that these compounds were distributed throughout the leaf, and were particularly concentrated in chlorophyll-containing cells. In V. vitis-idaea, most phenolic compounds were cell wall-bound and concentrated in the walls of the epidermis; this pool increased in response to UV-B enhancement. It is suggested that these two plants represent extreme forms of two divergent strategies for UV-B screening, the different responses possibly being related to leaf longevity in the two species. The response of V. uliginosum was intermediate between the other two, with high concentrations of cell wall-bound phenolics in the epidermis but with this pool decreasing, and the methanol-soluble pool tending to increase, after exposure to enhanced UV-B. One explanation for this response is that this plant is deciduous, like V. myrtillus, but has leaves that are structurally similar to those of V. vitis-idaea.     

Effects of enhanced UV-B radiation and elevated carbon dioxide concentrations on a sub-arctic forest heath ecosystem

An experiment is described which studies the effects of enhanced UV-B radiation (simulating a 15% reduction in the Ozone layer) and elevated atmospheric concentrations of CO₂ (600 ppm) on the dwarf shrub layer of a sub-arctic forest heath ecosystem at Abisko, North Sweden. The experimental treatments were first applied in 1993, and have covered most of the snow-free season (late May to early September) 1993–1995. Effects of the treatments on the four dwarf shrub species have been recorded largely using non-destructive measures (Vaccinium uliginosum, Vaccinium myrtillus – deciduous species and Vaccinium vitis-idaea and Empetrum hermaphroditum – evergreen species). Effects of the treatments on stem growth and leaf thickness have so far been small, although CO₂ treatments initially stimulated stem extension in Vaccinium myrtillus 1993 and depressed growth in V. vitis idaea in 1994 and E. hermaphroditum during 1995. UV-B treatments stimulated fruit production in V. myrtillus in both 1994 and 1995, but there was no effect on reproductive phenology. There were also marked effects of UV-B treatments on insect herbivory in the deciduous dwarf shrubs; with leaf area loss being greater than the control in the UV-B treatment in V. myrtillus and less in V. uliginosum. The results point to the possibility of important effects of the treatments on physiological and chemical processes within the plants. The ecological results of such effects may not be immediately apparent, but may be far reaching, pointing to the need for long-term in situ experimentation in predicting the effects of these global change variables.     

Effects of water and mineral nutrient supply on a deciduous and an evergreen dwarf shrub: Vaccinium uliginosum L. and V. vitisidaea L.

The effects of irrigation and fertilization on nutrient content, shoot growth and photosynthetic rate of the deciduous Vaccinium uliginosum L. and the evergreen V. vitis-idaea L. were studied in a field experiment at Abisko, Swedish Lapland. V. vitis-idaea responded to fertilization with a greater increase in leaf nitrogen, phosphorus and potassium concentrations, as well as with a relatively greater change in shoot growth than V. uliginosum . Also to irrigation did V. vitis-idaea respond more strongly. Decreased leaf longevity was indicated in both irrigated and fertilized plants of V. vitis-idaea . It is concluded that no general response pattern for evergreen and deciduous plants can be expected to emerge unless one also takes other plant characteristics, and also site characteristics, into consideration.     

Experimental studies on Vaccinium myrtillus and Vaccinium vitis-idaea in relation to air pollution and global change at northern high latitudes: A review

The aim of this paper is to review the experimental studies performed with two important species (i.e. Vaccinium myrtillus and Vaccinium vitis-idaea) of the shrub layer of boreal forests. The focus is on ecophysiology and stress tolerance under conditions of air pollution and global change. Our objective was to make an overview of studies of abiotic stress related to global change on the above species, and discuss the reported effects of these environmental factors. These issues include nitrogen, heavy metals, radionuclides, salt, ozone, carbon dioxide, warming climate, declining snow cover, periodic droughts, fire and elevated UV radiation. The findings suggest that both species are relatively tolerant to many abiotic environmental stresses: increased nitrogen and metal supply have negligible impacts on these species, as the atmospheric gaseous compounds reported. In some cases the effects are even positive, since extra nitrogen may improve the frost hardiness of V. vitis-idaea, and V. myrtillus may even benefit from elevated CO₂. Both species also seem to recover well from fires. However, the reports demonstrated that both have species-specific areas of weakness: (1) V. myrtillus is susceptible to stress caused by warming winter, and (2) frost hardiness of V. vitis-idaea may be reduced under enhanced UV radiation.     

Micro-site performance of evergreen and deciduous dwarf shrubs in a subarctic heath in relation to nitrogen status

The relationship between micro-site nitrogen status (total soil N conc., total vegetation N, and leaf N conc.) and performance (biomass) for two evergreen and two deciduous dwarf shrubs was studied in a subarctic heath. One deciduous species, Vaccinium uliginosum , dominated on sites having the highest vegetation nitrogen content and highest leaf nitrogen concentrations. The evergreen Empetrum hermaphroditum dominated on sites with a low total vegetation nitrogen content and low leaf nitrogen concentrations. Two other species, V. myrtillus (deciduous) and V. vitis-idaea (evergreen), showed intermediate patterns that were not clearly separated from either V. uliginosum or Empetrum . Soil nitrogen content showed no significant differences between micro-sites. Possible physiological reasons for the observed patterns are discussed.     

Differential responses of UK upland plants to nitrogen deposition

Native upland species, Nardus stricta , Eriophorum vaginatum , Erica cinerea and Vaccinium vitis-idaea were given 3 or 60 kg N ha⁻¹ yr⁻¹, over 2 yr, applied as a mist (NH₄NO₃). The high N treatment increased above-ground biomass in all four species, but only significantly in E. cinerea , E. vaginatum and N. stricta . Biomass increases in E. vaginatum and N. stricta resulted from enhanced tiller production rather than shoot elongation. Root growth increased in N. stricta , so that root:shoot ratio in this species was unchanged by N. Root growth in E. vaginatum , E. cinerea and V. vitis-idaea did not respond to N and their root:shoot ratios decreased. Tissue N concentrations increased in both shoots and roots of all species in response to N. The accumulated foliar N did not increase the proportion of N allocated to Rubisco and the photosynthetic capacities of N. stricta , E. vaginatum and V. vitis-idaea were unchanged. Thus growth responses to N were due to altered allocation rather than increased rate of photosynthesis per unit leaf area. The high N treatment increased flower production significantly in E. cinerea but not in the other species. Although in this experiment dwarf shrubs were more responsive than graminoids to N, in the field at current N inputs the enhanced tillering of the graminoids may be more competitively advantageous, especially where gaps develop in the canopy. Thus increasing N deposition may lead to increased grassiness of upland heath, and in particular, a spread of N. stricta .     

Time to chill: effects of simulated global change on leaf ice nucleation temperatures of subarctic vegetation

We investigated the effects of long-term (7-yr) in situ CO(2) enrichment (600 μmol/mol) and increased exposure to UV-B radiation, the latter an important component of global change at high latitudes, on the ice nucleation temperatures of leaves of several evergreen and deciduous woody ericaceous shrubs in the subarctic (68° N). Three (Vaccinium uliginosum, V. vitis-idaea, and Empetrum hermaphroditum) of the four species of shrubs studied showed significantly higher ice nucleation temperatures throughout the 1999 growing season in response to CO(2) enrichment and increased exposure to UV-B radiation relative to the controls. The same species also showed a strong interactive effect when both treatments were applied together. In all cases, leaves cooled to below their ice nucleation temperatures failed to survive the damage resulting from intracellular ice formation. Our results strongly suggest that future global change on a decadal time scale (atmospheric CO(2) increases and polar stratospheric O(3) destruction) will lead to increased foliage damage of subarctic vegetation by severe late spring or early autumnal frosting events. Indeed, in support of our experimental findings, there is now some evidence that increases in atmospheric CO(2) concentration over the past three to four decades may already have acted in this manner on high-elevation arboreal plants in the Swedish Scandes. The implications for vegetation modeling in a future "greenhouse" world and palaeoclimate estimates from high-latitude plant fossils dating to the high-CO(2) environment of the Mesozoic are discussed.     

Warming effects on growth,production, and vegetation structure of alpine shrubs: a five-year experiment in northern Japan

Warming effects on shoot growth, production, reproductive activity, and vegetation structure of alpine shrubs were measured over 5 years in a mid-latitude alpine fellfield in northern Japan. Open-top chambers (OTC) increased the daily mean air-temperature by 1.5-2.3 degrees C throughout the growing season but the effect on soil temperature was small. Two evergreen species, Ledum palustre and Empetrum nigrum, tended to increase their annual shoot production and aboveground-mass accumulation in the OTCs, whereas flower production did not differ. Two deciduous species, Vaccinium uliginosum and Arctous alpinus, increased their flower production in the OTCs, whereas the vegetative growth and mass accumulation did not change. No significant differences in vegetative and flower production were detected in Vaccinium vitis-idaea between the OTCs and control plots. The shoot survival and growth in terms of height of most species increased in the OTCs relative to the control treatment, and the growth rate was significantly different among species. As a result, interspecific competition seemed to be accelerated in the OTCs, and the less competitive V. vitis-idaea was suppressed by other plant species. The response to the warming observed in this study was rather different from that seen in arctic and subarctic plants even within the same species, indicating that the warming effect may cause different responses between arctic and mid-latitude alpine ecosystems. We concluded that the artificial warming over 5 years accelerated the growth of a few restricted species and lead to the change in vegetation structure in the mid-latitude alpine ecosystem.     

Surface morphology, leaf and cuticle thickness of four dwarf shrubs from a sub-Arctic heath following long-term exposure to enhanced levels of UV-B

In 1991 a field experiment was established in subarctic heathland at Abisko (68°35'N, 18°82'E), northern Sweden, to investigate the effects of enhanced UV-B (280–315 nm) radiation, simulating 15% ozone depletion, on plants in their natural environment. Leaves of the four dominant dwarf shrubs, the deciduous Vaccinium myrtillus L. and V. uliginosum L. and the evergreen V. vitis-idaea L. and Empetrum hermaphroditum Hagerup were examined after 7 years of UV-B treatment. SEM and ESEM were used to visualize surface features and to determine trichome density. Multiphoton laser scanning microscopy showed that UV-B absorbing compounds were localized in the trichomes of all species. Trichomes varied in size, number and distribution between the species. Enhanced UV-B reduced adaxial trichome density significantly (by approximately 25%) in only one species, V. uliginosum . This effect could be of importance for the UV-B absorbing potential of the adaxial epidermis of V. uliginosum . Epicuticular wax structures were found only on the abaxial surface of V. uliginosum and were unaffected by enhanced UV-B. The cuticular surfaces of all other species were smooth and featureless. Leaf thickness, adaxial and abaxial cuticle thickness varied between the species although there was no apparent effect of enhanced UV-B. It is concluded that long-term enhancement of UV-B has an effect on adaxial trichome density in V. uliginosum , but that there is no general effect on leaf morphology of the other species.     

Patterns of carbon allocation above ground in a deciduous (Vaccinium uliginosum) and an evergreen (Vaccinium vitis-idaea) dwarf shrub

The carbon allocation to current-year shoots of the deciduous Vaccinium uliginosum L. and the evergreen V. vitis-idaea L. was studied in a field experiment using ¹⁴C. During the first week after labelling, 0–50% and 30–80% of the initially assimilated ¹⁴C was lost in V. vitis-idaea and V. uliginosum respectively. Later on, the losses were smaller. After leaf fall in V. uliginosum , 30, 10 and 8% of the initially assimilated ¹⁴C was recovered in the abscised leaves, in plants labelled 1 July, 1 August and 1 September, respectively. The amounts found in the old V. vitis-idaea leaves the year after labelling were 33, 20 and 10%. Only traces of past-year assimilates were found in the current-year V. vitis-idaea leaves, while it was estimated that the V. uliginosum leaves contained 10–15% of the past-year label. It is concluded that V. vitis-idaea is mainly dependent on early summer assimilates - produced by leaves that have overwintered – for the current year shoot growth, while past-years' assimilates probably make an important contribution to the leaf expansion in V. uliginosum. When fruits occurred, a large fraction of the ¹⁴C assimilates was allocated to them.     

Responses of alpine shrubs to simulated environmental change during three years in the mid-latitude mountain, northern Japan

Effects of artificial warming on phenology, individual leaf traits, vegetative growth, and reproduction of five alpine species (two deciduous and three evergreen shrubs) were investigated during three years in the mid-latitude alpine, northern Japan. Eleven open-top chambers (OTCs) were set up on a fellfield (1680 m a. s. l.) in the Taisetsu Mountains by which air temperature at plant height was increased by ca 2°C. Vaccinium uliginosum (deciduous shrub) showed earlier leaf emergence in every season and earlier flowering only in the first season in the OTCs. By contrast, acceleration of leaf emergence in the OTCs was not clear for other species, i.e. Arctous alpinus (deciduous shrub). Ledum palustre. V. vitis-idaea , and Empetrum nigrum (evergreen shrub). Both deciduous species showed longer leaf life-span in the OTCs every season. All evergreen species had higher leaf survival rates in the OTCs. indicating extension of leaf life-span. Leaf nitrogen concentration and leaf mass per unit leaf area (mg cm ⁻²) generally tended to decrease in the OTCs. Relationships between the individual leaf traits and cumulative air temperature during the leaf developing period were not clear. Total leaf production during the three seasons increased in the OTCs in A. alpinus. L. palustre. V. vitis-idaea , and E. nigrum. All evergreen shrubs showed larger shoot growth in the OTCs but both deciduous shrubs did not show significant changes. In contrast to the vegetative growth, deciduous shrubs produced more flowers in the OTCs. Fruit production was not influenced by the OTCs for all species. The extension of photosynthetic period in the OTCs may contribute to the larger vegetative growth or flower production.     

Leaf mineral nutrition of Arctic plants in response to warming and deeper snow in northern Alaska

Articulating the consequences of global climate change on terrestrial ecosystem biogeochemistry is a critical component of Arctic system studies. Leaf mineral nutrition responses of tundra plants is an important measure of changes in organismic and ecosystem attributes because leaf nitrogen and carbon contents effect photosynthesis, primary production, carbon budgets, leaf litter, and soil organic matter decomposition as well as herbivore forage quality. In this study, we used a longterm experiment where snow depth and summer temperatures were increased independently and together to articulate how a series of climate change scenarios would affect leaf N, leaf C, and leaf C:N for vegetation in dry and moist tussock tundra in northern Alaska, USA. Our findings were: 1) moist tundra vegetation is much more responsive to this suite of climate change scenarios than dry tundra with up to a 25% increase in leaf N; 2) life forms exhibit divergence in leaf C, N, and C:N with deciduous shrubs and graminoids having almost identical leaf N contents; 3) for some species, leaf mineral nutrition responses to these climate change scenarios are tundra type dependent ( Betula ), but for others ( Vaccinium vitis-idaea ), strong responses are exhibited regardless of tundra type; and 4) the seasonal patterns and magnitudes of leaf C and leaf N in deciduous and evergreen shrubs were responsive to conditions of deeper snow in winter. Leaf N is was generally higher immediately after emergence from the deep snow experimental treatments and leaf N was higher during the subsequent summer and fall, and the leaf C:N were lower, especially in deciduous shrubs. These findings indicate that coupled increases in snow depth and warmer summer temperatures will alter the magnitudes and patterns of leaf mineral nutrition and that the long term consequences of these changes may feed-forward and affect ecosystem processes.     

分布尼泊尔至台湾的少齿越桔组(越桔属)

对越桔属Vaccinium中曾经被认为属于越桔组sect.Vitis-idoea的种或与之相关的76个运算上的分类单位进行数值分析,并记录了44个特片,解析如下:Vaccinium sect.Vitis-idoea应是局限于越桔V.vitis-idaca这个种而言;5个喜马拉雅的分类单位:V.nummularia,V.paucicrenatum,V．delavayi,V.retusum,V.moupinense,有2个表面上类似V.vitis-idaea的分类单位,运算上部是聚类在一起都被归入少齿越桔组scet.Aethopus.其余20个操作分类单位(OTU)包含10个分类单位,每个都十分特殊,但没有显著的片段的祥式可分辨。     

Short-term effects of simulated environmental change on phenology, leaf traits, and shoot growth of alpine plants on a temperate mountain, northern Japan

In order to assess the responses of circumpolar and semicircumpolar plants growing around their southern distribution margins to artificial warming, we set up 11 open-top chambers (OTCs) on a fell-field (1680 m a.s.l.) in the Taisetsu Mountains, northern Japan. The OTCs increased mean air temperature by 1.3°C through the growing season (June–September) and extended the length of the growing season. We examined phenology and leaf traits of plants in the OTCs and control plots during the first season under artificial warming treatment using two deciduous and three evergreen species. Ledum palustre (evergreen shrub), Vaccinium uliginosum , and Arctous alpinus (deciduous shrubs) showed earlier leaf emergence and/or flowering in the OTCs. Deciduous shrubs had longer individual leaf longevity and an extended foliage period in the OTCs than in the control plots. There were no significant differences in specific leaf area and leaf size for many species between the OTCs and the control plots. Vaccinium vitis-idaea (evergreen shrub), L. palustre, A. alpinus , and Empetrum nigrum (evergreen shrub) had lower leaf nitrogen concentration in the OTCs than in the control plots, whereas it was higher in V. uliginosum . Only E. nigrum showed larger annual shoot growth in the OTCs. No clear differences in response to the warming effect were detected between evergreen and deciduous species in the first season. Circumpolar plants growing in temperate alpine regions may be more affected by season length rather than temperature itself.     

Photosynthetic and respiratory responses to temperature and light of three Alaskan tundra growth forms

Photosynthetic and respiratory response of four Alaskan tundra species comprising three growth forms were investigated in the laboratory using an infrared gas analysis system. Vaccinium vitis-idaea , a dwarf evergreen shrub, demonstrated a low photosynthetic capacity: P_max= 1 mg CO₂ g dry wt⁻¹ h⁻¹; T_opt < 10°C. Betula nana , a deciduous shrub, had a high relatively photosynthetic capacity: P_max= 14 mg CO₂ g dry wt⁻¹ h⁻¹; T_opt 17°C. Two graminoid (sedge) species, Carex aquatilis and Eriophorum vaginalum , showed different responses. Carex showed a high photosynthetic capacity: P_max= 20 mg CO₂ g dry wt⁻¹ h⁻¹; T_opt 22°C. Eriophorum vaginatum demonstrated an intermediate photosynthetic capacity of 4 mg CO₂ g dry wt⁻¹ h⁻¹ at saturated light levels. Leaf dark respiration, up to 20°C, was approximately the same for all species. The patterns of root respiration among species was opposite to the trend in photosynthesis. Vaccinium vitis-idaea had the highest rate of root respiration and B. nana the lowest ( C aquatilis was not measured). Correlation between leaf nitrogen content (%) and photosynthetic capacity was high. Hypothesized growth form relationships explained differences in photosynthetic capacity between the deciduous shrub and evergreen shrub, but did little to account for differences between the two sedges. Differences in rooting patterns between species may affect tissue nutrient content, carbon flux rates, and carbon balance.     

Ambient ultraviolet radiation in the Arctic reduces root biomass and alters microbial community composition but has no effects on microbial biomass

We assessed the effects of ambient solar ultraviolet (UV) radiation on below‐ground parameters in an arctic heath in north‐eastern Greenland. We hypothesized that the current UV fluxes would reduce root biomass and mycorrhizal colonization and that these changes would lead to lower soil microbial biomass and altered microbial community composition. These hypotheses were tested on cored soil samples from a UV reduction experiment with three filter treatments (Mylar, 60% UV‐B reduction; Lexan, up to 90% UV‐B reduction+UV‐A reduction; UV transparent Teflon, filter control) and an open control treatment in two study sites after 3 years' manipulation. Reduction of both UV‐A and UV‐B radiation caused over 30% increase in the root biomass of Vaccinium uliginosum, which was the dominant plant species. UV reduction had contrasting effects on ericoid mycorrhizal colonization of V. uliginosum roots in the two sites, while it had no clear effects on fungal (ergosterol) or microbial biomass (measured both with fumigation–extraction and quantitative lipid biomarker analysis) in soil. However, principal component analysis of lipid biomarkers (phospholipid and glycolipid fatty acid profiles) showed that microbial community composition was altered by UV reduction. Although the UV responses were slight considering the large dose difference between the treatments (from near‐ambient to up to 90% UV‐B reduction), we cannot rule out the possibility that the recovery of ozone layer would change the below‐ground functioning of arctic ecosystems.     

Effects of nitrogen addition on the stress sensitivity of Calluna vulgaris

The effects of low levels of nitrogen addition (7·7 and 15·4 kg N ha⁻¹ yr⁻¹) on plant sensitivity to biotic and abiotic stress were studied at a lowland heath in the south of England that has received N treatments since 1989. Larval growth rates and adult weights of heather beetles were found to be significantly higher when insects were reared on plants that had received additional N, with implications for insect survival and reproductive success. Electrolyte leakage measurements failed to reveal any significant impact of N addition on plant sensitivity to frost episodes in early winter. In April, however, there was some evidence of slightly decreased frost hardiness in plants receiving additional N. Accelerated spring bud burst also suggested earlier physiological activity in N-treated plots. The rate of water loss from excised shoots of Calluna vulgaris (L.) Hull was significantly faster in plants receiving additional N, although no difference in plant water potential was measured in the field after a prolonged dry spell. Whilst experimental N addition had only a small effect on plant sensitivity to abiotic stress, the relationship between enhanced deposition and increased insect performance was clear, with the potential for substantially increased insect damage at deposition rates around the critical load contributing to the formation of gaps in the Calluna canopy.     

The effects of long-term elevation of air temperature and CO on the frost hardiness of Scots pine

The frost hardiness of 20 to 25-year-old Scots pine (Pinus sylvestris L.) saplings was followed for 2 years in an experiment that attempted to simulate the predicted climatic conditions of the future, i.e. increased atmospheric CO₂ concentration and/or elevated air temperature. Frost hardiness was determined by an electrolyte leakage method and visual damage scoring on needles. Elevated temperatures caused needles to harden later and deharden earlier than the controls. In the first year, elevated CO₂ enhanced hardening at elevated temperatures, but this effect disappeared the next year. Dehardening was hastened by elevating CO₂ in both springs. The frost hardiness was high (相似文献   

Does ice crystal formation in buds explain growth disturbances in boron-deficient Norway spruce?

Loss of apical dominance in boron-deficient trees has been suggested to be due to frost damage of terminal buds and leaders. Excessive nitrogen (N) supply can exacerbate boron (B) deficiency by the dilution-effect. N may also have direct effects on winter hardiness. We studied frost hardening of buds of Norway spruce (Picea abies L. Karst.) in healthy-looking trees and in trees with growth disturbances. The effect of B and N on frost hardiness was studied in a factorial fertilisation experiment during cold acclimation. Frost hardiness was determined by differential temperature analysis (DTA) and scoring of visual damage. In a DTA profile of apical buds with a piece of stem, low-temperature exotherm (LTE) predicted bud injury, while two of the observed high-temperature exotherms and two of the observed intermediate-temperature exotherms were non injurious. Appearance of LTE followed changes in air temperature. The risk of frost damage was not affected by fertilisation treatments or previously observed growth disturbances. However, when the bud structure was deformed by severe B deficiency, the supercooling ability disappeared. Such buds are probably killed by freezing in nature and therefore, frost damage may play a secondary role in the development of growth disturbances.