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PubMed2000

Genetic basis of climatic adaptation in scots pine by bayesian quantitative trait locus analysis.

We examined the genetic basis of large adaptive differences in timing of bud set and frost hardiness between natural populations of Scots pine. As a mapping population, we considered an "open-pollinated backcross" progeny by collecting seeds of a single F(1) tree (cross between trees from southern and northern Finland) growing in southern Finland. Due to the special features of the design (no marker information available on grandparents or the father), we applied a Bayesian quantitative trait locus (QTL) mapping method developed previously for outcrossed offspring. We found four potential QTL for timing of bud set and seven for frost hardiness. Bayesian analyses detected more QTL than ANOVA for frost hardiness, but the opposite was true for bud set. These QTL included alleles with rather large effects, and additionally smaller QTL were supported. The largest QTL for bud set date accounted for about a fourth of the mean difference between populations. Thus, natural selection during adaptation has resulted in selection of at least some alleles of rather large effect.

Acclimatization↗
PubMed2000

The electrical impedance spectroscopy of Scots pine (Pinus sylvestris L.) shoots in relation to cold acclimation.

Electrical impedance spectroscopy (EIS) was applied to stems of Scots pine (Pinus sylvestris L.) in a provenance field trial during frost hardening to find an EIS parameter for assessing frost hardiness (FH) without a controlled freezing test. The FH of stems and needles assessed by controlled freezing tests was compared with the equivalent circuit EIS parameters of a distributed model of stems (not exposed to controlled freezing treatment) and with dry matter (DM) content of stems. Significant differences in the equivalent circuit parameters, FH and DM content were found between provenances. The relaxation time (tau(1)), describing the peak of the high frequency arc of the impedance spectrum, and the intracellular resistance (r(i)) of stems increased with increasing FH. According to the linear regression, the coefficient of determination (R(2)) between the FH of stems and needles with tau(1) of the stem was 0.87 and 0.89, and with r(i) of the stem 0.74 and 0.85, respectively. The relation between FH and tau(1) changed with the degree of hardiness. The highest coefficient of determination was 0.95 in September when the FH of needles, ranging from -10 degrees C to -25 degrees C, was predicted with an accuracy of +/-2.0 degrees C. The resistance parameter r(2), describing the width of the low frequency arc of the impedance spectrum, decreased prior to and during the initial hardening: significant differences were found between provenances. This indicates that r(2) was not related to frost hardening per se. It is concluded that it is possible to distinguish the hardening patterns of different provenances by tau(1) in the rapid phase of hardening without controlled freezing tests.

Acclimatization↗
PubMed1992

Patterns in aboveground carbon allocation and tree architecture that favor stem growth in young Scots pine from high latitudes.

The production and allocation of aboveground biomass and the characteristics of tree architecture were examined in eight-year-old Scots pine (Pinus sylvestris L.). Considerable among-tree variation existed in tree architecture, total aboveground dry mass production, and dry mass partitioning among tree parts. A linear relationship existed between needle and branch mass. Stem mass was directly proportional to tree height, which in turn was directly proportional to the allocation ratio between stem mass and total needle + branch mass production. The architectural characteristics that were related to a high proportional allocation to stem and high stemwood production were a large mean shoot volume, large mean number of branches per whorl, long needle retention and a high crown length/crown width ratio. Individual trees were found that combined high stemwood production with both high harvest index and high stemwood specific gravity.

Journal Article↗
PubMed1992

Photosynthesis of a Scots pine shoot: a comparison of two models of shoot photosynthesis in direct and diffuse radiation fields.

Two models of shoot photosynthesis, the needle surface element model (SEM) and needle volume element model (VEM), were tested against empirical data obtained from measurements of the photosynthetic response of twelve Scots pine (Pinus sylvestris L.) shoots in direct and diffuse radiation. The models assume that shoot photosynthesis is obtained as the integrated response of either all needle surface area elements (SEM) or all needle volume elements (VEM) of the shoot. The models differ in that needles are treated as optically black in SEM, whereas in VEM radiation penetrates into the needle. The photosynthetic response of a surface/volume element was described as a Blackman-type curve and the distributions of irradiance on the elements were derived by computer simulation, based on a model of shoot geometry. The parameters (initial slope and maximum rate) of the Blackman-curve of an element were estimated iteratively by the method of least squares, i.e., by minimizing the residual sum of squares of simulated and measured rates of shoot photosynthesis. The parameter estimation was done separately for direct and diffuse radiation, and the models were evaluated based on the notion that, for the "ideal" model, the estimated parameter values should be the same in direct and diffuse radiation. Both models produced shoot photosynthesis curves that agreed well with measurements, but there was a discrepancy in the estimated parameter values, indicating that differences in the photosynthetic response of shoots in direct and diffuse radiation could not be explained solely on the basis of the simulated irradiance distributions. The agreement was, however, much better for the volume element model, which accounts for penetration of radiation into the needles.

Journal Article↗
PubMed1993

Effect of ammonium on glutamine synthetase activity in ectomycorrhizal fungi, and in mycorrhizal and non-mycorrhizal Scots pine seedlings.

The influence of ammonium on glutamine synthetase activity (GS, EC 6.3.1.2) was studied in three species of ectomycorrhizal fungi, Paxillus involutus (Batsch:Fr) Fr, Piloderma croceum Erikss. and Hjortst. and Suillus variegatus (Fr) O Kuntze growing in pure culture, as well as in the roots and needles of nursery-grown, non-mycorrhizal and mycorrhizal Scots pine (Pinus sylvestris L.) seedlings inoculated with Paxillus involutus or Piloderma croceum as the symbiont. In response to increasing concentrations of ammonium in the nutrient solution, GS activity (expressed on a dry weight basis) increased slightly in Suillus variegatus but not in the other fungi. Glutamine synthetase activity increased in the roots and decreased in the needles of non-mycorrhizal seedlings as the ammonium concentration in the nutrient solution was increased from 0 to 1 mM, but no response was noted with further increases from 1 to 12 mM. Interspecies differences in GS activity were noted among the fungi growing in pure culture, but no significant interspecies differences were observed among the same fungi in the mycorrhizal state.

Journal Article↗
PubMed1993

Needle polyamine concentrations and potassium nutrition in Scots pine.

The response of free polyamines (putrescine, spermidine and spermine) in needles of Scots pine (Pinus sylvestris L.) to varying needle potassium concentrations was investigated in two potassium fertilization experiments on drained peatlands. A significant negative correlation was observed between putrescine and potassium concentrations in needles. Putrescine responded more sensitively to decreasing needle K concentrations during the growing season than during the winter. Putrescine accumulation started when needle potassium concentrations were above 5.5 mg g(dw) (-1) in summer and above 5.0 mg g(dw) (-1) in winter. A decrease in needle potassium concentrations below 4.3 mg g(dw) (-1) in summer and below 3.5 mg g(dw) (-1) in winter resulted in an exponential increase in putrescine concentrations. Putrescine accumulation was initiated well above the needle potassium concentrations generally considered indicative of deficiency. The exponential increase in putrescine concentrations in winter occurred within the range of needle potassium concentrations that has been identified as indicating severe potassium deficiency.

Journal Article↗
PubMedDate not supplied

Dependence of light interception efficiency of Scots pine shoots on structural parameters.

The ratio of shoot silhouette area to total needle area (STAR) is one means of quantifying the light interception efficiency of a coniferous shoot. The silhouette area (or STAR) of a shoot depends on various structural characteristics of the shoot, and also varies with the direction of the shoot relative to the direction of radiation (sun angle). The mean STAR taken over all directions in space is the mean ratio of shoot silhouette area to total needle area in an isotropic radiation field. It also represents a mean STAR with respect to a spherical shoot orientation. In this study, equations for the relationship between mean STAR and easily measurable shoot characteristics were developed. The STAR values in different directions were determined from photographically measured shoot silhouette areas. Mean STAR varied between 0.079 and 0.308, and averaged 0.146. A clear increase in mean STAR with age was found. The material consisted of 305 Scots pine (Pinus sylvestris L.) shoots from Sweden and Finland, representing shoots of different age and a wide variation in site fertility. The needle area density in the shoot cylinder, together with the diameters of the shoot cylinder and the twig explained 87% of the variation in mean STAR.

Journal Article↗
PubMed1995

Acid phosphatase activity and phosphorus nutrition in Scots pine needles.

From March to October, acid phosphatase activity and phosphorus (P) concentration were measured in four needle age classes of the upper and lower crowns of fertilized and unfertilized Scots pine (Pinus sylvestris L.) trees. Negative correlations between acid phosphatase activity and P concentration were observed in current-year needles and in needles in the upper part of the crown, whereas there was a positive correlation between enzyme activity and P concentration in older needles and in needles in the lower part of the crown. In May and October, needles of all ages showed increased acid phosphatase activity. The most sensitive response of acid phosphatase activity to phosphate supply and phosphorus status of the whole tree was seen in current-year needles on the first whorl where a 300% increase in acid phosphatase activity was observed in response to a decrease in foliar P concentration of 1.7-1.8 mg P g(DW) (-1).

Journal Article↗
PubMed1995

Effects of needle age, long-term temperature and CO(2) treatments on the photosynthesis of Scots pine.

Naturally regenerated 20-25-year-old Scots pine (Pinus sylvestris L.) trees were grown in open-top chambers in the presence of an elevated temperature or CO(2) concentration, or both. The elevated temperature treatment was administered year-round for 3 years. The CO(2) treatment was applied between April 15 and September 15 for 2 years. The photosynthetic responses of 1- and 2-year-old needles to varying photon flux densities (0-1500 micro mol m(-2) s(-1)) and CO(2) concentrations (350, 700 and 1400 micro mol mol(-1)) during measurement were determined. The CO(2) treatment alone increased maximum photosynthetic rate and light-use efficiency, but decreased dark respiration rate, light compensation and light saturation regardless of needle age. In contrast, the temperature treatment decreased maximum photosynthetic rate and photosynthetic efficiency, but increased dark respiration rate, light compensation and light saturation. The aging of needles affected the photosynthetic performance of the shoots; values of all parameters except photosynthetic efficiency were less in 2- than in 1-year-old needles. The CO(2) treatment decreased and the temperature treatment enhanced the reduction in maximum photosynthesis due to needle aging.

Journal Article↗
PubMedDate not supplied

Viability and seasonal distribution patterns of Scots pine pollen in Finland.

Germination ability and airborne counts of Scots pine (Pinus sylvestris L.) pollen were studied during the spring of 1993 at Turku in southern Finland (60 degrees 32' N, 22 degrees 28' E) and at Utsjoki in northern Finland (69 degrees 45' N, 27 degrees 01' E). Pollen waas trapped from the beginning of May to the end of June in a high-volume air sampler. Germination tests were performed to determine the in vitro pollen viability of the trapped pollen. Airborne pine pollen counts were obtained from a continuously operating Burkard trap located near each high-volume sampler. When male flowering began, phenological observations were carried out on pollen grains collected in rotored samplers located in pine and spruce stands and open fields near Turku and Utsjoki. In southern Finland, the peak period of pine pollen production was short, lasting for only 3 days, but it accounted for about 80% of the total germinating pine pollen yield for the year. The peak count was on May 20, with over 2000 germinating pollen grains per cubic meter of air. Pollen germination rates of up to 70% were obtained during the week preceding the local pollen peak, and rates reached almost 90% on the peak day. Pollen viability remained at 45 to 65% for 1 week after the peak. There was no significant difference between the pollen counts for day and night, indicating that during the main pollen season, the pollen source was close to Turku. Before the local pollen peak, the counts of living pine pollen were low, indicating that pine pollen transported over long distances was of little ecological importance in 1993 in the Turku area. In northern Finland, the first pollen grains were caught on July 4, and the peak day was July 13. However, no viable pollen was observed during this period, indicating that there was little gene drift from southern to northern Finland in 1993.

Journal Article↗
PubMed1996

Response of LAI-2000 estimates to changes in plant surface area index in a Scots pine stand.

We assessed the accuracy with which the LAI-2000 plant canopy analyzer measured changes in leaf area index (LAI) and plant area index (PAI) in a 25-year-old Scots pine (Pinus sylvestris L.) stand. Stand density was 2100 stems ha(-1) and mean tree height was 8.7 m. Needle and branch areas of the stand were reduced progressively to zero by the stepwise removal of branches on all trees growing in a circular plot with a radius of 25 m. An LAI-2000 estimate was taken after each step reduction. The needle and branch surface areas removed at each step were estimated from direct measurements and were compared with the changes in the LAI-2000 estimates. Initially (before removal of branches), directly measured PAI was 5.2 (needles = 86%, branches = 8% and stems = 6%). The LAI-2000 estimate of total surface area was 66% of direct PAI and 77% of direct LAI. There was a nonlinear relationship between the LAI-2000 estimate and directly measured PAI, such that their ratio (equivalent to the clumping factor) increased from 0.66 to 1.05 with decreasing PAI. At the last measurement, when only stems were left, the LAI-2000 estimate agreed well with the direct measurement of PAI. The LAI-2000 underestimated the direct measurement of LAI at the first three steps when LAI was > 2 and the proportion of woody area was small (< 20%). However, because the LAI-2000 estimate included stem and branch areas, it overestimated the direct measurement of LAI at the last three measurements when the proportion of woody area was large (> 20%).

Journal Article↗
PubMed1996

Hydraulic conductance, light interception and needle nutrient concentration in Scots pine stands and their relations with net primary productivity.

Aboveground xylem hydraulic conductance was determined in Scots pine (Pinus sylvestris L.) trees and stands from 7 to about 60 years of age. At the stand scale, leaf area index and net primary productivity (NPP, above- plus belowground) increased and reached a plateau at about 25-30 and 15-20 years, respectively; both parameters declined in mature stands. Stand hydraulic conductance followed a similar trend to NPP, with a maximum at about 15-20 years and a pronounced reduction in old stands. At the tree scale, annual biomass growth per unit of leaf area (growth efficiency) declined with tree age, whereas aboveground sapwood volume per unit leaf area, which is linearly related to maintenance respiration costs, steadily increased. Radiation interception per unit leaf area increased significantly with reduced leaf area index of mature stands, despite increased foliage clumping in the canopies of mature trees. Needle nutrient concentration did not change in the chronosequence. Tree hydraulic conductance per unit leaf area was strongly and positively correlated with growth efficiency. We discuss our findings in the context of growth reductions in mature and old trees, and suggest that increased hydraulic resistance and maintenance respiration costs may be the main causes of reduced carbon gain in mature and old trees.

Journal Article↗
PubMed1997

Relationship between temperature, respiratory loss of sugar and premature dehardening in dormant Scots pine seedlings.

Increased intracellular sugar concentration is an important contributor to the increased cold tolerance of conifers in winter. This study examines the extent to which wintertime respiratory loss of sugars leads to premature dehardening. Two-year-old seedlings of Scots pine (Pinus sylvestris L.), grown and cold-hardened in the field, were exposed to different temperature regimes for 16 weeks while dormant. To minimize short-term carry-over effects, after the temperature treatments, all seedlings were conditioned to 5.5 degrees C and watered before the assessment of non-structural carbohydrates and cold tolerance. Needle sugar concentration was decreased by 54, 32, 21 and 9% following treatment at 5.5, 0, -1.5 and -8.5 degrees C, respectively. Sugar concentration did not decrease as much in root tissues as in needles because starch was mobilized in roots. Cold tolerance of needles was analyzed by controlled freezing, and the temperature causing an initial 10% damage (LT(10)) was plotted as a function of needle sugar concentration, revealing a strong, linear relationship. When one-third of the initial sugars had been consumed, LT(10) had increased from -24.5 to -16.5 degrees C, and when one half had been consumed, LT(10) had increased to -10 degrees C. Consequences of these findings for the field performance of conifers are discussed in relation to climatic variation and change.

Journal Article↗
PubMed1997

Effects of foliar potassium concentration on morphology, ultrastructure and polyamine concentrations of Scots pine needles.

We examined the effects of three foliar potassium concentrations (high, intermediate and low) on the morphology, ultrastructure and polyamine concentrations of current-year and 1- and 2-year-old needles of 30-year-old Scots pine (Pinus sylvestris L.) trees. Foliar K concentration had only a slight effect on needle morphology. The sclerenchyma cell walls were thinner, the xylem area was larger, and the resin ducts were smaller in needles with a low K concentration than in needles with a high or intermediate K concentration. In addition, the bundle sheath cells were collapsed in needles having a low K concentration. The secondary growth of phloem tissue and the mesophyll area were greater in needles with a high or intermediate K concentration than in needles with a low K concentration, possibly indicating greater production of photoassimilates in these trees. At the ultrastructural level, mesophyll cells with enlarged central vacuoles and small vacuoles containing electron-dense material were common in needles having a low K concentration. Enlargement of the central vacuole coincided with an exponential increase in putrescine concentration in needles with a low K concentration, suggesting that the central vacuole may function as a storage site for putrescine.

Journal Article↗
PubMed1997

Distribution of elements along the length of Scots pine needles in a heavily polluted and a control environment.

Pollution often causes visible symptoms of foliar injury. The injury is sometimes associated with an increase in the accessibility of toxic elements to plants as a result of acidification of the soil. We investigated the distribution of elements (N, P, K, Ca, Mg, Mn, S, Fe, B, Cu, Zn, Al, F, Pb, Cd, Cr, Ni and Co) in healthy current-year needles of Scots pine (Pinus sylvestris L.) growing at an unpolluted control site and at a site polluted mainly by SO(2), HF and Al(3+) from a fertilizer factory established in 1917. Needles from both sites were sampled before the appearance of visible injury and cut into five sections of equal length (tip, base and three middle parts). The mean concentrations of major nutrients were 20-30% lower in needles at the polluted site than in needles at the control site, whereas the concentrations of aluminum and fluorine were higher in needles at the polluted site. An increase in concentration from needle base to tip was detected for N, Fe, B, and Al at both sites and for Mn only at the polluted site. Fluoride accumulated in the tips of needles only at the polluted site, which could explain the necroses of needle tips at this site. The distribution of elements along the length of the needles was influenced by pollution, element mobility and the distal accumulation of toxic elements.

Journal Article↗
PubMed1997

Biomechanical and hydraulic determinants of tree structure in Scots pine: anatomical characteristics.

The development of anatomical, hydraulic and biomechanical properties in Scots pine (Pinus sylvestris L.) stems aged 7 to 59 years was followed. The hydraulic diameter and length of tracheids increased with age to a maximum at 15 and 35 years, respectively. Number of tracheids per unit of sapwood area decreased with age to a minimum of 500-600 tracheids mm(-2). Variations in specific hydraulic conductivity and Young's modulus of stems were associated with variation in anatomical properties. Over the time sequence considered, hydraulic and mechanical properties were positively related to each other and followed a similar developmental pattern, with no suggestion of a trade-off between the two. For most of the tree's life-cycle, heartwood made only a small contribution to whole-section mechanical stiffness because of its location close to the flexural neutral axis, and because of the presence of juvenile wood.

Journal Article↗
PubMed1997

Photosynthetic responses of Scots pine to elevated CO(2) and nitrogen supply: results of a branch-in-bag experiment.

Naturally seeded Scots pine (Pinus sylvestris L.) trees, age 25-30 years, were subjected to two soil-nitrogen-supply regimes and to elevated atmospheric CO(2) concentrations by the branch-in-bag method from April 15 to September 15 for two or three years. Gas exchange in detached shoots was measured in a diffuse radiation field. Seven parameters associated with photosynthetic performance and two describing stomatal conductance were determined to assess the effects of treatments on photosynthetic components. An elevated concentration of CO(2) did not lead to a significant downward regulation in maximum carboxylation rate (V(cmax)) or maximum electron transport rate (J(max)), but it significantly decreased light-saturated stomatal conductance (g(sat)) and increased minimum stomatal conductance (g(min)). Light-saturated rates of CO(2) assimilation were higher (24-31%) in shoots grown and measured at elevated CO(2) concentration than in shoots grown and measured at ambient CO(2) concentration, regardless of treatment time or nitrogen-supply regime. High soil-nitrogen supply significantly increased photosynthetic capacity, corresponding to significant increases in V(cmax) and J(max). However, the combined elevated CO(2) + high nitrogen-supply treatment did not enhance the photosynthetic response above that observed in the elevated CO(2) treatment alone.

Journal Article↗
PubMed1999

Effects of elevated atmospheric CO(2) on phenology, growth and crown structure of Scots pine (Pinus sylvestris) seedlings after two years of exposure in the field.

Three-year-old Scots pine (Pinus sylvestris L.) seedlings were grown for two years in the ground in open-top chambers supplied with either an ambient or elevated (ambient + 400 &mgr;mol mol(-1)) CO(2) concentration. Phenological observations and measurements of height and stem diameter growth, absolute and relative growth rates, starch and soluble carbohydrate concentrations of the needles, and crown structure and needle properties were made at frequent intervals throughout the two growing seasons. Elevated CO(2) significantly advanced the date of bud burst in both years. The increase in total needle area in response to elevated CO(2) was accounted for by longer shoots and an increase in individual needle area in the first year, and by an increase in the number and length of shoots in the second year. Stem diameter and tree height were enhanced more by the elevated CO(2) treatment in the first year than in the second, indicating a decreased effect of CO(2) on growth over time. This was confirmed by a study of absolute and relative growth rates of leader shoots. During the first growing season of CO(2) enrichment, mean weekly relative growth rates over the growing season (RGR(m)) were significantly enhanced. During the second year, RGR(m) in ambient CO(2) closely matched that in elevated CO(2).

Journal Article↗