Contents of ATP and ADP in needles of Norway spruce in relation to their development,age, and to symptoms of forest decline

Summary Pool sizes of ATP and ADP were analysed in freeze-stopped, lyophilised homogenates of needles from Norway spruce [Picea abies (L.) Karst.]. Control experiments in which possible changes in adenylate pools during sample acquisition were investigated did not reveal significant differences between needles taken from branches in situ or within a 30-min period after cutting off a branch. In addition, pool sizes of ADP and ATP were not affected by changes in light intensity (between 60 and 1500 E^*-m^-2*s^-1), which inevitably occur when samples have to be taken from the upper region of older trees. Levels of ATP and ADP showed considerable seasonal changes (May through October) with the highest ratios of ATP/ADP in developing needles. In general, there was a tendency towards increased ratios of ATP/ADP with increasing needle age. This observation was corroborated by analyses of needles from spruce trees of different age and growing under different conditions. Needles from declining trees or from trees specifically fumigated with low concentrations of ozone and sulphur dioxide had significantly increased ratios of ATP/ADP compared to controls. The results are discussed with respect to physiological responses connected with natural senescence and induced ageing.     

Needle CO2 exchange, structure and defense traits in relation to needle age in Pinus heldreichii Christ – a relict of Tertiary flora

 Pinus heldreichii Christ is a long-lived, slow-growing Tertiary relict from the Balkans. In this study we evaluated the physiological characteristics of eight needle-age classes of P. heldreichii grown at the Arboretum of the Institute of Dendrology in Kórnik, Poland. At the end of the growing season, current-year foliage had the highest rates of mass-based light-saturated net photosynthesis (A_sat) of 33.5 nmol CO₂· g^–1· s^–1. A_sat decreased with needle age, but older needle classes retained from approximately 62 to 26% of the current needles’ rate. The relationship between leaf N and chlorophyll a concentration among all needle-age classes was highly significant (r = 0.96, P = 0.0006). The variation in A_sat of 1- to 7-year-old needles was linearly related to needle N concentration (r = 0.98, P = 0.0001). Needle dark respiration rates among these needle age classes ranged from 0.8 to 2.2 nmol · g^–1· s^–1 and decreased with needle age and nitrogen concentration. Total phenols and glucose concentrations increased linearly with needle age. A similar pattern was observed in acid buffering capacity and the pH of tissue homogenates. The water content ranged from 62% for the current needles to 51% for the 6-year-old needles. Greater investment in leaf structural tissue and increased chemical defense is associated with higher structural cost of older needles and may reduce their photosynthetic activity. Significant declines in water and nitrogen content with needle age and an increase in content of phenolics is most likely a defense adaptation of P. heldreichii related to the species’ long-lived leaves. Received: 8 January 1997 / Accepted: 4 March 1997     

Activities of enzymes of starch metabolism in developing Norway spruce [Picea abies (L.) Karst.] needles

 Development of spruce needles starts with high levels of starch. These are derived from imported sucrose, and, with some fluctuation, largely vanish during sink/source transition (Hampp et al. 1994, Physiol Plant 90: 299 – 306). In order to get more information about starch metabolism during this period, we collected current year needles of approximately 25-year-old Norway spruce trees [Picea abies (L.) Karst.] for up to 100 days starting from bud break. Levels of extractable activities of α-amylase (EC 3.2.1.1), ADP-glucose pyrophosphorylase (AGP, EC 2.7.7.27), D-enzyme (4-α-D-glucotransferase; EC 2.4.1.25), and of starch phosphorylase (STP, EC 2.4.1.1.) exhibited specific development-related responses. Insoluble starch dissolving α-amylase was close to the limit of detection for up to 70 days after bud break. At this stage, which marked the start of sink/source transition, α-amylase showed a rise in activity which could be related to the activity of sucrose phosphate synthase, a key enzyme of sucrose formation (correlation coefficient r = + 0.93). Similarly, the activity of AGP, a key enzyme of starch synthesis, was low during the initial phase of needle development and started to increase from about 60 days onwards. STP and D-enzyme, both involved in starch cycling, differed from each other. While STP activity changed in parallel to that of AGP, it was only the D-enzyme which showed appreciable rates shortly after bud break. We thus assume that in spruce needles D-enzyme is mainly responsible for starch turnover during the early period of development, whereas needle maturation, i. e. the acquisition of the ability to export photoassimilates, is characterized by an increased turnover of transitory starch – both synthesis (AGP) and degradation (α-amylase, STP) – and this is closely connected to the emergence of activity of the key enzyme of sucrose synthesis, sucrose phosphate synthase. Received: 16 October 1995 / Accepted: 20 February 1996     

Assimilation,allocation and utilization of carbon by 3-year-old Scots pine (Pinus sylvestris L .) trees during winter and early spring

 The photosynthetic capacity of frost-hardy and frost-sensitive needles of 3-year-old Scots pines and the allocation and utilization of assimilated carbon was examined during winter and early spring. The photosynthates of the whole trees were labelled by ¹⁴CO₂ fixation and after chase periods of from 7 days to 4 months under natural climatic conditions, the distribution of radiocarbon in the various tissues of the trees was determined. During winter maximal photosynthetic rates of 1-year-old needles were considerably lower than in summer when calculated on a leaf area basis. However, when related to the chlorophyll content these discrepancies disappeared. The decrease of the photosynthetic capacity upon frost-hardening could be attributed to a two- to three-fold reduction in the chlorophyll content of the needles. The pulse-chase experiments showed that photosynthesis during the cold season preferentially provides substrates for respiration. Half of the assimilated ¹⁴C was respired during the first week, and after chase periods of 3 – 4 months the trees contained not more than 10 – 20% of the radiocarbon. The carbon, which was exported by the needles, was translocated basipetally via the twigs and the stem to the roots. Whereas in the axial system incorporation of radiocarbon into storage compounds, like starch, and into cell wall material was almost negligible during the cold season, in the roots one-third of the radiocarbon was recovered from starch 2 months after the ¹⁴C-pulse. In contrast to the above-ground parts of the trees, where starch content was very low during winter, in the roots considerable amounts of starch, up to 450 μmol hexose units · g^– 1 DW, were found even during mid-winter. In early spring the radiocarbon in the cell wall-, lipid-, and starch-fraction accounted for more than 80% of the ¹⁴C recovered at that time from the axial system. Incorporation of minor quantities into the cell wall fraction of the roots during winter and early spring indicate continuous root growth during the cold period as well as in early spring. Whereas during winter the buds did not attract freshly assimilated carbon, in spring just before bud break substantial amounts of carbon were translocated from the needles into the buds. In contrast, remobilization of carbon, which had been assimilated during autumn of the previous year, and import into the sprouting buds could not be demonstrated. Received: 3 November 1995 / Accepted: 1 March 1996     

Distribution patterns of foliar carbon and nitrogen as affected by tree dimensions and relative light conditions in the canopy of Picea abies

 Variations in the partitioning of foliar carbon and nitrogen in combination with changes in needle and shoot structure were studied in trees of Picea abies along a vertical gradient of relative irradiance (RI). RI was the major determinant of needle morphology, causing all needle linear parameters – width, thickness and length – to increase. Due to the different responsiveness of needle thickness and width in respect of RI, the ratio of total to projected needle area increased with RI. Furthermore, shoot structure was also influenced by RI, and the ratio of shoot silhouette area to total needle area, which characterises the packing of needles and needle area within the shoot, was greater at lower values of irradiance. Needle dry weight per total needle area (LWA_t) was also increased by RI. Similarly, irrespective of the measure for surface area, needle nitrogen content per area, as the product of needle dry weight per area and nitrogen content per needle dry weight (N_m), scaled quasi-linearly with needle weight per area. Thus, the changes in needle and shoot morphology made it possible to invest more photosynthesising weight per unit light-intercepting surface there, where the pay-back due to elevated irradiances was the highest. However, N_m behaved in an entirely different manner, decreasing hyperbolically with LWA_t. Since non-structural (carbon in non-structural carbohydrates), and structural (total minus non-structural) needle carbon per dry weight also increased with LWA_t, N_m was inversely correlated with both non-structural and structural carbon. Total tree height, increasing significantly LWA_t, also influenced needle structure. It appeared that total height did not affect needle thickness or width, but larger trees had greater needle density (dry weight per volume). Because needle density was positively correlated with needle carbon content per dry weight, it was assumed that the greater values of needle carbon content can be attributed to increased lignification and thickening of needle cell walls. Thus, it appeared that the proportion of supporting structures was greater in needles of larger trees. Inasmuch as an increased fraction of supporting structures dilutes other leaf substances, including also leaf compounds responsible for CO₂-assimilation, enhanced requirement for supporting structures may be responsible for lower rates of carbon assimilation per foliage dry weight observed in large trees. Increasing water limitation with increasing tree size is discussed as a possible cause for increased needle supporting costs in large trees. Received: 2 April 1995 / Accepted: 16 February 1996     

Seasonal variation in the monoterpenes in needles of Picea abies (L.) Karst.

Summary This investigation was conducted to obtain information about the fluctuations in composition and amount of needle monoterpenes during the development of spruce needles. Studies conducted with two Norway spruce clones clearly revealed the existence of fluctuations. In juvenile needles, the amounts of the oxygenated terpenes increase constantly with age during the first 2 months of needle growth. The hydrocarbon terpenes dominate within the first weeks, some of them even showing a very distinct first maximum within the first 3 weeks after bud burst. All terpenes, including the oxygenated ones, have a maximum in June/July, which favours the hypothesis of a substitution of the hydrocarbons later on. There are significant changes even in mature needles of Norway spruce. The terpene level of 1-year-old needles of the clonal trees increased from spring to early summer and then dropped again towards winter. In addition, fluctuations in mature needles were shown for a set of ten wild trees. Needles of the same age class, which emerged in 1986, were sampled 4 times from 1986 to 1988. The needle terpene concentrations of the 1 -year-old needles were considerably lower in spring at the time of bud burst than in autumn. The terpene level of older needles thus seems to be influenced by biosynthetic and catabolic activities.     

Control of Adventitious Root Production and Hypocotyl Hypertrophy of Sunflower (Helianthus annuus) in Response to Flooding

Needles of 20-year-old Scots pine trees (Pinus silvestris L.) were permitted to photoassimilate ¹⁴CO₂ for 1 h on different dates during the growing season. The loss of radioactivity from current, 1-year-old, and 2-year-old needles was followed, and the translocation of photoassimilated ¹⁴CO₂ from older needle age-classes to the elongating new needles studied. The effects of good mineral and water supply on translocation were also considered. In the spring, 1-year-old and 2-year-old needles accumulated ¹⁴C. These reserves, together with current photosynthate, were utilized when the trees started growing. The 1-year-old needles exported ¹⁴C to the current needles during the first weeks of elongation of the later, while no such translocation occurred from the 2-year-old needles. Removal of the 1-year-old needles resulted in translocation of assimilates from the 2-year-old needles to the current needles. The general pattern of translocation observed in the control trees was not changed when the trees were fertilized and irrigated. The new needles started to export assimilates in the middle of July when the photosynthetic rate per needle was comparable with that of the older age-classes. This occurred about 4 weeks after positive net photosynthesis was first measured for the current shoot. The current needles of trees with good nutrient and water supply seemed to become self-sufficient in photoassimilates earlier than the current needles of the control trees.     

Nitrogen storage and remobilization in ash (Fraxinus excelsior) under field and laboratory conditions

 Storage and remobilization of nitrogen (N) were studied in ash trees (Fraxinus excelsior) under both field and greenhouse conditions. Experiments in the greenhouse providing ¹⁵N labelled fertilizer to the trees showed that the major quantity of N remobilized during subsequent spring was from the roots, and only a small amount from the stem. This corresponded with a loss of soluble N (proteins and low-molecular-weight compounds) from both roots and stem. On the two field sites, which differed in water availability, there was a decrease in bark N content during leaf growth, but on the dry site net N export from the bark was sustained throughout the whole vegetation period. Remobilized N was derived from soluble proteins and low-molecular-weight compounds on the moist site, which was demonstrated by the seasonal dynamics of a 56 kDa polypeptide in bark and wood. On the dry site, lower contents of soluble proteins were associated with smaller amounts of N remobilized compared to the moist site. Uptake studies of ¹⁵N labelled fertilizer indicated a higher contribution of current uptake to leaf N increment during spring at the dry site compared to the moist site. Differential N availability during the season had a decisive effect on the nitrogen storage dynamics at the two sites. Thus the influence of current N supply on N remobilization and storage as found in the greenhouse-grown plants could be verified under field conditions. Received: 28 July 1995 / Accepted: 17 July 1996     

Scots pine needle injuries at subarctic industrial sites

 Injuries to needles of Scots pines (Pinus sylvestris L.) growing in nutrient-poor soils on the Kola Peninsula collected in April 1991 were studied on a gradient of increasing distances (10 – 115 km) from the Monchegorsk nickel smelter, Russia, which emits SO₂, Ni and Cu. The condition of the mesophyll cells was quantified from needles of the two latest age classes using a light and an electron microscope. The damage to the ultrastructure consisted of multistress symptoms caused by excess sulphur, heavy metals, frost, acidic precipitation and ozone. Injuries were most commonly manifested in the form of dark, irregularly shaped chloroplasts with protrusions and light thylakoids and plastoglobuli. These symptoms gradually disappeared with increasing distance and decreasing deposition rate. Concentrations of sulphur, copper and nickel decreased towards more distant sites where normal levels of the latter two elements were reached. Sulphur concentrations remained above background throughout the distance gradient. In the closest plots to the smelter area, cell collapse under the stomata and epidermis related to acute SO₂ and heavy metal effects was found, whereas further away symptoms were more diverse, pointing towards the effects of ozone, acidic deposition and thereby decreased frost tolerance. The additive multistress symptoms were clearly seen in the area up to 40 km from the smelter where needle Cu concentration was above 110 ppm, Ni concentration above 39 ppm and S concentration above 1343 ppm. Received: 22 October 1995 / Accepted: 17 October 1996     

The Influence of the urban environment on the composition of terpenes in the needles of Black Pine (Pinus nigra Arnold)

 The composition of terpenoid substances in needles of Pinus nigra Arnold with respect to air pollution is discussed. Trees grown in the urban environment of the city of Nitra, which is contaminated by immissions, and trees grown in the relatively clean environment of the Mlyňany Arboretum SAS were investigated. The urban environment caused a change in the species composition and the content of terpenes. In the city of Nitra needles of P. nigra contained a smaller number of terpenoid substances (12 terpenes) in comparison with the Arboretum (15 terpenes). At Nitra P. nigra contained four terpenes with a relative portion above 1% and at the Mlyňany Arboretum P. nigra needles contained six terpenes above 1%. At the polluted site citral, eugenol, and bisabolol are completely missing in the terpene pattern of needles and myrcene, carvone and alfa-humulene were notably lower. The decrease of the alfa-pinene content and the increase of the beta-pinene content in needles from Nitra significantly lowered the ratio of alfa-pinene to beta-pinene from 2.80 to 0.86. Received: 27 October 1995 / Accepted: 29 March 1996     

Quantitative analysis of abscisic acid in needles of Abies alba Mill. by electron capture gas chromatography

Summary The amount of abscisic acid (ABA) in needles of silver fir from a natural location was investigated with regard to position in the crown, damage, seasonal variation, and needle age. Because of problems of quantification of ABA in coniferous needles, which contain numerous secondary plant products, a method for reliable determination of both isomers cis-trans-ABA (c-ABA) and transtrans-ABA (t-ABA) was developed. By means of gas chromatography (GC) using an electron capture detector (BCD) and a programmed temperature vaporizer (PTV) injector complete separation of both compounds was achieved. Two different pairs of fir were investigated — in each case a damaged and a healthy tree. Needles from both trees from the first and the second pair collected in September contained 500–1100 ng c-ABA/g fresh weight (FW), and the concentrations of t-ABA varied from 400 to 700 ng/g FW. Investigations from the second pair show highest amounts of 2900 ng/g Fw c-ABA and 1800 ng/g FW of t-ABA in May and June. For the first pair a higher c-ABA content was found in needles from the top of the crown than in those from the middle and the base. This difference could not be confirmed in the analysis of the second pair. Because of the strong natural deviation no statistically significant difference between the healthy and the damaged tree was found. The first pair of firs examined showed a higher t-ABA concentration than the second one. In this case the highest amount was found in the top of the crown. Methodical mistakes during the clean-up procedure and in quantification by gas chromatography could be excluded. The presence of c- and t-ABA in the purified extract was corroborated by mass spectrometry. With regard to the seasonal variation both isomers of ABA show an unequivocal trend. The maximum concentration is achieved in May to June, whereas the content is minimal in August/September. In any case the level of t-ABA is lower than that of c-ABA. No correlation between the amount of ABA and the needle age could be established.     

“Lateral Control”: Phytohormone Relations in the Conifer Treetop and the Short- and Long-Term Effects of Bud Excision in Abies nordmanniana

In a conifer tree, such as Nordmann fir, Abies nordmanniana Spach, the leader bud and its immediate surroundings play a decisive role in crown architecture. As subapical branch buds are segregated from the leader meristem, resource allocation between ortho- and plagiotropic growth is determined. The relationship between treetop buds in young trees was studied in the natural state and after surgical removal in early July of either the leader bud (decapitation) or the subapical whorl branch buds (destipitation). The two bud types showed consistent cytokinin profile differences but similar seasonal dynamics in cytokinins and auxin (IAA). After bud excision, ZRP increased dramatically in the subapical stem within 1 h, followed by ZR within 1 week. Supernormal levels of ZR were maintained through autumn and persisted in spring in the destipitated trees, but had returned to normal in the decapitated trees. The treetop buds remaining after bud excision experienced an immediate decrease in most cytokinins, followed, however, by a large surplus later in the season. The following spring this high level persisted in the leader bud of destipitated trees, but not in whorl buds of decapitated trees. Conspicuous growth pattern changes followed from destipitation, but few from decapitation. Growth reactions suggest that resource allocation to main branch buds inhibits leader growth in normal trees, a kind of “lateral control.” Auxin and ABA content in buds and stems was largely unaffected by treatments. Data suggest that subapical leader tissues beneath the apical bud group are a primary source of cytokinin regulation.     

Seasonal dynamics of chlorophyll and microelement content in developing conifer needles of <Emphasis Type="Italic">Abies sibirica</Emphasis> and <Emphasis Type="Italic">Picea abies</Emphasis>

Composition of microelements and photosynthetic pigment content (chlorophylls (Chl) a and b) were monitored in growing needles of spruce (Picea abies (L.) Karst.) and Siberian fir (Abies sibirica Ledeb.) during spring-autumn vegetation period. The dynamics of fresh weight and needle length for the first-year needles of spruce and fir revealed a number of shared and species-specific features in growth patterns of photosynthetic organs. In the beginning of growth period (in May), the needles elongated rapidly, while June–July were marked by the increase in needle weight. In P. abies the needle weight accumulated rapidly (specific growth rates μ_max up to 0.20 day⁻¹) over a short period (14 days), while in A. sibirica the needle weight increased slower (μ_max ≤ 0.11 day⁻¹) but over a longer period (≥30 days). The dynamics of Chl a and Chl b content and their ratio were identical in needles of both species over the growth period, although changes in Chl a were pronounced stronger than those in Chl b. In spring (May), a relatively high total Chl content per needle dry weight was noted. In summer (June–August), the total Chl content declined appreciably. In autumn (September–November), the total chlorophyll content in first-year needles increased slightly. Microelements were classified into two groups according to seasonal dynamics of their relative content in first-year needles. The first group includes Ba, Mn, Zn, B, Cu, Co, Cr, Pb, and Mo, whose relative content had a distinctive maximum in July, coincident with the peak in Chl content. The second group comprises Ni, V, Ag, Be, Cd, and As, whose relative content was minimal at this period. Seasonal changes in microelement composition were similar for the two conifer species examined, which is likely due to different physiological values of various microelements for photosynthetic organs.     

Energy requirement for foliage construction depends on tree size inyoung Picea abies trees

 The relationship between stand biomass production, and tree age and size is generally a curve with a maximum. To understand why wood production decreases in the final stages of stand development, the influence of increasing tree size on foliage chemical composition and substrate requirement for foliage construction in terms of glucose [CC, g glucose (g dry mass)^{–  1}] was investigated in the evergreen conifer Picea abies (L.) Karst. Because it was already known that irradiance affects both foliage morphology and chemistry in this species, and it was expected that the foliage in large overstory trees would intercept on average more light than that in saplings in understory, irradiance was measured in the sampling locations and included in the statistical models. CC of needles increased with increasing total tree height (TH) and was independent of relative irradiance. A major reason for increasing CC with increasing TH was a greater proportion of carbon-rich lignin in the needles in large trees. However, lignin did not fully account for the observed changes in CC, and it was necessary to assume that certain other carbon-rich secondary metabolites such as terpenes also accumulate in the foliage of large trees. Enhanced requirements for needle mechanical strength as evidenced by greater lignin concentrations in large trees were attributed to increased water limitations with increasing tree height. Because water relations may also control the sink capacities for assimilate usage, apart from the mechanical requirements, they may provide an explanation for the accumulation of other energetically expensive compounds in the needles as well. Biomass partitioning within the shoot was another foliar parameter modified in response to increasing tree size. The proportion of shoot axes, which serve to provide needles with mechanical support and to supply them with water, decreased with increasing TH. This may limit water availability in the needles, and/or manifest a lower water requirement of the needles containing proportionally more supporting and storage substances, and consequently, less physiologically active compounds such as proteins. Probably the same factors which caused CC of the needles to depend on TH, were also responsible for greater CC of the shoot axes in larger trees. These results collectively suggest that increasingly more adverse water relations with increasing tree size may provide a mechanistic explanation for the decline in foliar biomass and its functional activity during stand ageing. Received: 9 April 1996 / Accepted: 14 January 1997     

Effect of defoliation on tracheid production and the level of indole-3-acetic acid in Abies balsamea shoots

To simulate feeding by the spruce budworm ( Choristoneura fumiferana Clem.), the apical current-year shoots on 1-year-old branches in the uppermost whorl of 6-year-old balsam fir [ Abies balsamea (L.) Mill.] trees were either removed completely by debudding before the start of the growing season or defoliated 0, 50, 90 or 100% shortly after budbreak. Debudded branches were treated at the apical end with 0, 0.1 or 1.0 mg of indole-3-acetic acid (IAA) (g lanolin)⁻¹. Ninety % of the 1-year-old needles were also removed from some of the experimental branches. After ca 4 weeks of growth, the radial width of new xylem and the level of IAA were determined in the 1-year-old internode. The IAA content was measured by radioimmunoassay.
The removal or defoliation of current-year shoots inhibited tracheid production and decreased the IAA level. Exogenous IAA stimulated tracheid production and increased the IAA level in debudded branches. Current-year shoot defoliation also inhibited current-year shoot elongation. The inhibitory effect of current-year needle removal on all parameters generally increased with increasing intensity of defoliation. The removal of 1-year-old needles did not affect the IAA level or current-year shoot elongation, nor did it influence tracheid production in branches with current-year shoots. However, removal of 1-year-old needles inhibited tracheid production in debudded branches supplied with exogenous IAA. The results indicate that (1) IAA is involved in the control of tracheid production in the 1-year-old internode, (2) IAA is supplied primarily by current-year shoots, and (3) defoliation by the spruce budworm inhibits tracheid production partly by decreasing the supply of IAA.     

The effect of nutrition on the seasonal course of needle respiration in Norway spruce stands

 Respiration of 1-year-old needles of 30-year-old Norway spruce trees [Picea abies (L.) Karst.] was studied in a nutrient optimisation experiment in northern Sweden. Respiration rates of detached needles, from ten control (C) and ten irrigated-fertilised (IL) trees, were measured on 16 occasions from June 1992 to June 1993. The aim of the study was to determine the influence of temperature on the seasonal course of needle maintenance respiration, and the effect of nitrogen concentration [N] and carbohydrate content on needle respiration in young Norway spruce trees subjected to long-term fertilisation. The IL treatment significantly affected needle size, in terms of dry mass and length, but not specific needle length (SNL). There was, however, a strong tree-specific effect on SNL (P<10^–9, R ² = 0.75). Needle starch content varied markedly with season (0–25% of total dry mass). This, unless accounted for, would cause erroneous estimates of nutrient concentrations, and of rates of needle respiration, within and between treatments. There was considerable seasonal variation in needle respiration, both in terms of maintenance respiration and temperature dependence (Q₁₀). Q₁₀ had its highest value (2.8) during winter and its lowest (2.0) in the middle of summer. In early autumn (August, September), respiration rate and needle [N] were significantly related (C: P = 0.001, IL: P<0.0005). There was no significant difference in the slope between the two regression lines, but a difference in intercept. At the same needle [N], needles from IL-plots always had a lower respiration rate than needles from control plots. No obvious explanation for the observed difference in intercept was found, but some plausible assumptions are put forward and discussed. Received: 24 January 1997 / Accepted: 1 July 1997     

Accumulation and Retranslocation of Mineral Nutrients in Developing Needles in Relation to Seasonal Growth of Young Radiata Pine Trees

The growth, accumulation and movement of mineral nutrients (nitrogen,phosphorus, potassium (calcium) and chlorophyll in needles ofyoung radiata pine trees (Pinus radiata D. Don) were examined,from bud break in spring through the following year. Retranslocationof nutrients from needles was measured and is discussed in relationto nutrient requirements for seasonal growth. During the first 4–5 months after bud break when mostneedle growth occurred, all nutrients and chlorophyll accumulatedprogressively, although the concentrations of nitrogen, phosphorusand potassium decreased. During summer, substantial amounts of phosphorus were withdrawnfrom needles less than 6 months old, regardless of positionon the tree and silvicultural practice. In young needles andunder certain environmental conditions, this led to a markedtemporary decline in concentrations, even in fertilized treeson a fertile site. However, the phosphorus content of needleswas quickly restored following autumn rains. Similar fluctuations,including nutrient withdrawal in summer, occurred for nitrogenand potassium, but these were smaller than those observed forphosphorus. Phosphorus was also withdrawn from relatively olderneedles during summer. It was estimated that on a tree basis 86, 48 and 39 per centof the phosphorus, nitrogen and potassium, respectively, insummer shoots could have come from the retranslocation of nutrientsfrom young needles formed during the preceding spring. These results highlight the importance of nutrients stored inneedles to meet the nutrient requirements for growth when environmentalfactors may not be conducive to nutrient uptake from the soil. Pinus radiata D. Don, mineral nutrition, retranslocation, phosphorus, nitrogen, seasonal effects, pine needle growth     

Monoterpene levels in needles of Douglas fir exposed to elevated CO2 and temperature

Monoterpene levels in current year needles of Douglas fir ( Pseudotsuga menziesii (Mirb.) Franco) seedlings were measured at the end of 4 years of exposure to ambient or elevated CO₂ (+179 µmol mol⁻¹), and ambient or elevated temperature (+0.3.5^C). Eleven monoterpenes were identified and quantified using gas chromatography/flame ionization detector/mass spectroscopy, with eight of these compounds regularly occurring in all trees examined. Elevated CO₂ exposure significantly reduced the levels for four of the eight main compounds in needles. Total monoterpene production was reduced by 52% ( P  < 0.05). Elevated temperature also reduced monoterpene levels ( P  < 0.07). The combination of elevated temperature and elevated CO₂ resulted in a 64% reduction in total monoterpenes compared with needles on ambient temperature trees. Two-way anova showed no significant temperature-CO₂ interaction. It is hypothesized that seasonal reductions in needle monoterpene pools under elevated CO₂ and temperature conditions may be due to a combination of competing carbon sinks, including increased carbon flux through the roots.     

UV-B induction of flavonoid biosynthesis in Scots pine (Pinus sylvestris L . ) seedlings

 Cultivation of Scots pine (Pinus sylvestris L.) seedlings under simulated global radiation including the UV-B band (280 – 320 nm; 220 mW m^–2 UV-B_BE) led to increased formation of the diacylated flavonol glucosides 3″,6″-di-p-coumaroyl-astragalin and 3″,6″-di-p-coumaroyl-isoquercitrin in primary and cotyledonary needles, respectively. 3″,6″-Di-p-coumaroyl-astragalin was also the main constitutive diacylated flavonol glucoside in both needle types. This compound predominantly accumulated in primary needles upon UV-B irradiation, and reached concentrations of 2.4 μmol g^–1 fresh weight (fw). Its concentration was only weakly affected in cotyledonary needles. 3″,6″-Di-p-coumaroyl-isoquercitrin was mainly induced in cotyledonary needles with maximum concentrations of 0.8 to 0.9 μmol g^–1 fw, but was virtually unaffected in primary needles under the same irradiation conditions. Pulse labelling with L-(U-¹⁴C)phenylalanine revealed that these metabolites were formed de novo. Phenylalanine ammonia-lyase (EC 4.3.1.5) and chalcone synthase (EC 2.3.1.74) were only slightly induced by the UV-B treatment. The results described here represent the first report on UV-B-induced flavonoid biosynthesis in a conifer species. Received: 5 December 1995 / Accepted: 20 March 1996     

Conifer decline in the north-east of France: Characteristic changes in chloroplast protein pattern and absence of anti-oxidative defense capability point to an involvement of ozone

A method yielding intact and biologically active chloroplasts from needles of mature spruce ( Picea abies L. cv. Karsten) or fir ( Abies alba Mill.) growing in the field is presented. Using this method, chloroplasts were prepared from yellow and green needles of declining spruce and fir from two forest areas of the Vosges mountains (north-east of France). Both quantitative and qualitative changes could be shown in the two-dimensional chloroplast protein pattern of yellowing needles, as compared to that of apparently healthy needles. We observed that an accumulation of photosystem II D1-protein in the thylakoids was associated with needle decline. Furthermore, a lack of resistance capability against free radical attack was observed in yellow needles. We have attempted to correlate our observations with pollutant levels and we propose that, in the forest areas studied, O₃ is one of the main factors involved in conifer decline. It also appears from our results that decline and senescence are distinct phenomena.