Needle Dry Weight Research Articles

The impact of green spruce aphid, Elatobium abietinum (Walker), on the growth of young Sitka spruce in Hafren forest, Wales: delayed effects on needle size limit wood production

Defoliation of 3-year-old Sitka spruce ( Picea sitchensis (Bong.) Carr.) by green spruce aphid ( Elatobium abietinum (Walker)), in a field experiment in Hafren forest, Wales, resulted in significantly shorter shoots being produced in the upper canopy in 1994, the year of infestation, and in 1995. The dry weight (DW) of individual needles produced by defoliated trees was also reduced, by up to 19%, but whereas in 1994 the DW of the new needles was reduced only on the most heavily infested branches, in 1995 needle DW decreased throughout the canopy. In 1996, needles produced by previously defoliated trees were 10.4% heavier, on average, than needles produced by undefoliated trees. The total numbers of new needles produced by defoliated and undefoliated trees in 1994 and 1995 were similar, but defoliated trees produced 10% fewer needles in 1996. Consequently, and as a result of the changes in individual needle DW, the total DW of current-year needles on defoliated trees was 11% less than that on undefoliated trees in 1994, 20% less in 1995, and about the same in 1996. Stem volume increment of individual trees was related to the total DW of current-year needles ( r 2=0.43–0.52, p<0.001), and reductions in increment of 6% in 1994 and 24% in 1995 following E. abietinum infestation could be attributed to the reductions in total and individual needle DW. These results are in accordance with the known dependency of cambial growth in young conifers on the photosynthetic production of the current foliage, and the changes in individual needle DW provide an explanation, therefore, for the delayed effect of E. abietinum on diameter and volume increment of the experimental trees. Annual height growth, in contrast, was weakly related to the total DW of current-year needles in 1994 and 1995 ( r 2=0.16–0.26), and showed no relationship in 1996, indicating further that reductions in leader length following infestation, which were not correlated with reductions in stem diameter and volume increment, were caused by a different mechanism. Mechanisms likely to have caused the changes in individual needle DW are discussed.

Variation in specific needle area of old-growth Douglas-fir in relation to needle age, within-crown position and epicormic shoot production.

Variation in specific needle area (SNA; cm2 projected fresh needle area g-1 oven-dried needle weight) was investigated in relation to needle age, within-crown position and epicormic shoot production in 450-year-old Douglas-fir (Pseudotsuga menziesii Mirb. (Franco) var. menziesii) trees. Specific needle area decreased with increasing needle age. The magnitude and rate of change in SNA with needle age were greatest for lower-crown branches, and decreased toward the middle- and upper-crown branches. For all branches, there was no difference between regular and epicormic shoots in the relationship between SNA and needle age. Specific needle area decreased with increasing distance from branch base, and this relationship was significant for the majority of needle age classes of the upper- and middle-crown branches. In the lowercrown branches, SNA did not vary with distance from branch base for the majority of needle age classes. For all branches, there was no difference between regular and epicormic shoots in the relationship between SNA and distance from branch base for the majority of needle age classes. These results indicate that renewal of foliage by epicormic shoot production maintains needle quality. Branch SNA increased linearly with decreasing height in the crown at a mean rate of 0.951 +/- 0.110 cm2 g-1 per vertical meter. Total needle area of branches was estimated from total needle dry weight taking into account within-branch variation in SNA. Analyses of allometric relationships between branch size and foliage amount (needle area and needle dry weight) showed that branch length was a better predictor of foliage amount than branch diameter for old Douglas-fir trees. Total needle dry weight and needle area of the sample trees, estimated from branch length and branch height and taking into account vertical within-crown variation in branch SNA, ranged from 42.4 to 154.2 kg and from 246.2 to 816.0 m2 per tree, respectively.

Total soluble proteins amount in vegetative buds and needles of norway spruce during the bursting time

The vegetative buds and later on young needles as well as needles formed in spring previous year of Picea abieswere used in the experimental work. Extracted proteins were determined spectrophotometrically and the amount of dry weight was measured. The data revealed that the dry weight of needles formed in spring previous year was about three times higher than in the vegetative buds at the beginning of investigations. During the sampling period the dry weight in those needles was keeping nearly the same level (39-54%). The increase in dry weight was noticed in the young needles 5-6 weeks after vegetative buds burst. The amount of total soluble proteins in the needles formed previous year was about 140 mg/g of dry weight and it was uniformed during the investigation period. In the vegetative buds the amount of proteins was three times higher than in needles. But, the concentration starts to decrease just before bursting of the vegetative buds as well as during next 2 or 3 weeks when young shoot proliferated...

A retrospective early test ofPinus sylvestrisseedlings grown at wide and dense spacing

Stored seeds from 30 open-pollinated families that had been field tested for 28 years provided a retrospective opportunity to assess the efficiency of early testing in Scots pine (Pinus sylvestris L.). Seedlings height at the end of first (HGP1), second (HGP2) and third growth period (HGP3), and in the third growth period, leader length (LEADER3), basal stem diameter (DIA3), number of stem units (NSU3), mean stem unit length (MSUL3), aboveground fresh weight (AGFWT3), stem dry weight (STDWT3), and shoot and needle dry weight (SHNDWT3) were studied under wide and dense spacing. Families differed at the 1 or 0.1% level of probability. Differences between spacing were significant at the 0.01% level of probability for all traits measured in the third growth period. Families interacted significantly with spacing for HGP2, HGP3, LEADER3, AGFWT3, SHNDWT3 and MSUL3. Interactions were due to rank changes and the interaction component of variance varied from 26 to 96% of the family variance. Estimates of hi2over wide and dense spacing ranged between 0.23 ± 0.11 (HGP2) and 0.51 ± 0.14 (NSU3). Spacing did not alter the variance structure, hi2for each trait under wide or dense spacing were similar. However, spacing affected the phytotron-field genetic correlations. The average of 80 genetic correlation estimates was 0.52 under wide spacing and 0.29 under dense spacing. Averaged over eight field traits, the efficiency of indirect juvenile selection for the field traits indirect-direct selection percentage ranged from -15% for NSU3 under dense spacing to 99% for HGP3 under wide spacing.

Soluble proteins and dehydrins in nitrogen‐fertilized Scots pine seedlings during deacclimation and the onset of growth

Deacclimation of Scots pine (Pinus sylvestris) in northern Finland (65°N) was studied from the perspective of protein metabolism, which was related to nitrogen fertilization. Two‐year‐old seedlings were fertilized with calcium ammonium nitrate (0, 442 and 884 kg N ha−1) in the summer prior to the study. Needles were harvested for analyses at 3‐week intervals during the natural deacclimation period from mid‐March to the beginning of June 1998. Deacclimation was followed by monitoring various physiological variables: freezing resistance decreased and osmotic potential increased during the experiment and needle dry weight increased from bud flushing onwards. The concentration of soluble proteins in needles was higher in fertilized seedlings but decreased transiently in the 884 kg N ha−1 fertilized seedlings before budbreak. The abundance of several small polypeptides (17–32 kDa) decreased in the spring. A 60‐kDa protein, identified by immunoblotting as a dehydrin, was detected in all treatments. The quantity of this dehydrin decreased with resumption of growth, along with the appearance of 50‐ and 56‐kDa dehydrins. The concentration of these dehydrins decreased during dehardening more rapidly in fertilized seedlings than in the control plants. The fertilized seedlings started to grow earlier than the unfertilized plants. In conclusion, nitrogen fertilization provided good reserves for new growth but did not affect deacclimation of pine needles.

Estimating the needle area from geometric measurements: application of different calculation methods to Norway spruce

Different calculation methods, based on needle geometry, for estimating both projected area (PLA) and total surface area (TLA) of foliage in Norway spruce [Picea abies (L.) Karst.] were compared. Seventy-eight shoots of four age classes were sampled from both the basal and top thirds of crowns. Three dimensions (the length, minor and major diameters) of needles were taken, and the needle shape was approximated to a parallelepiped or ellipsoid. There was a perfect coincidence of the measured and estimated values of PLA calculated as the width of the needle projection multiplied by needle length, and corrected for needle taper (method III), or when the needle projection was treated as a rectangle joined with half-ellipses at both ends (method IV). The most reliable estimations of TLA resulted from treating the needle sides as faces of the parallelepiped tapering at their ends in the form of half-ellipses. The ratio of TLA to PLA ranged from 2.2 to 4.0 depending on the needle morphology. Needle minor diameter (anatomical width; D1) was found to be a better morphological index of the spruce foliage than needle flatness, i.e. the ratio of major to minor diameter. Expressing the factor for converting PLA to TLA as a function of D1 considerably improved the precision of the estimates. Close relationships were established between specific leaf area, expressed on both a projected area (SLAP) and total surface area basis (SLAT), needle dry weight (R2 was 0.799 and 0.852, respectively) and minor diameter of needles (R2 was 0.701 and 0.554, respectively).

A retrospective early test of &lt;i&gt;Pinus sylvestris&lt;/i&gt; seedlings grown at wide and dense spacing

Stored seeds from 30 open-pollinated families that had been field tested for 28 years provided a retrospective opportunity to assess the efficiency of early testing in Scots pine (Pinus sylvestris L.). Seedlings height at the end of first (HGP1), second (HGP2) and third growth period (HGP3), and in the third growth period, leader length (LEADER3), basal stem diameter (DIA3), number of stem units (NSU3), mean stem unit length (MSUL3), aboveground fresh weight (AGFWT3), stem dry weight (STDWT3), and shoot and needle dry weight (SHNDWT3) were studied under wide and dense spacing. Families differed at the 1 or 0.1% level of probability. Differences between spacing were significant at the 0.01% level of probability for all traits measured in the third growth period. Families interacted significantly with spacing for HGP2, HGP3, LEADER3, AGFWT3, SHNDWT3 and MSUL3. Interactions were due to rank changes and the interaction component of variance varied from 26 to 96% of the family variance. Estimates of hi2 over wide and dense spacing ranged between 0.23 ± 0.11 (HGP2) and 0.51 ± 0.14 (NSU3). Spacing did not alter the variance structure, hi2 for each trait under wide or dense spacing were similar. However, spacing affected the phytotron-field genetic correlations. The average of 80 genetic correlation estimates was 0.52 under wide spacing and 0.29 under dense spacing. Averaged over eight field traits, the efficiency of indirect juvenile selection for the field traits indirect-direct selection percentage ranged from -15% for NSU3 under dense spacing to 99% for HGP3 under wide spacing.

Seasonal growth and needle fall in Pinus sylvestris and P. uncinata

In this work, we study monthly development of tree-ring, elongation of branches, needle fall for Pinus sylvestris L., Pinus uncinata Ram. in the Spanish Central Pyrenees during 1993. Tree-ring formation happens from early June to late September, but most tree-ring growth happens from mid June to mid July. P. sylvestris starts its tree-ring development before P. uncinata. P. uncinata begins its growth of shoots earlier than its tree-ring growth. Needle fall reaches its maximum in autumn. P. uncinata shows a delayed maximum rate of needle fall, a longer period of fall of most of its needles compared to P. sylvestris. This delay, the greater needle dry weight, and the smaller average radial diameter of P. uncinata tracheids compared with P. sylvestris, show P. uncinata adaptations to environments with more stress.

The influence of pH on root morphology and mineral content of Pinus pinaster Ait. seedlings

ABSTRACT Two-week old seedlings of Pinus pinaster Ait. were grown in nutrient solutions at pH values ranging from 3.5 to 6.5. Acidity exerted a different influence on the growth of the main and lateral roots, thus changing the morphology of the whole root system. Roots grown at pH 3.5 had the shortest length, but the highest biomass and were markedly thickened. The total number of 2nd order lateral roots per plant was not significantly influenced by pH, whereas their length and the development of 3rd order roots were the highest at pH 3.5 and the lowest at pH 6.5. Mineral nutrition was affected by the pH of the culture solution. The P and Fe concentrations in roots were higher in the pH 3.5 and 4.5 solutions than in pH 5.5 and 6.5. In contrast, lower K, Ca, Mg and especially Mn contents were found in the roots grown at pH 3.5. However, needle dry weight was unaffected by low pH and neither chlorosis nor critical levels of mineral elements were observed. These results suggest that the compensatory growth of lateral roots allows P. pinaster seedlings to maintain an adequate nutritional status in the shoot even under highly acidic conditions.

Growth and Water Use of Red Spruce (Picea Rubens Sarg.) Exposed to Ozone and Simulated Acidic Precipitation for Four Growing Seasons

Abstract Red spruce (Picea rubens Sarg.) saplings from a pristine site in Maine were transplanted in native soil to 360 liter pots and relocated to Ithaca, New York. After a 1 yr establishment period, 90 saplings were chosen for use, assigned to treatments, placed in large open-top chambers, and exposed to ozone (0.5 to 2.0 x ambient concentration) and simulated acidic precipitation (at pH 3.1, 4.1, or 5.1) for 3 or 4 consecutive growing seasons (total ozone exposures of about 165 ppm · hr to almost 570 ppm · hr). Forty-five trees were grown on weighing lysimeters and were used to develop whole-tree water-use budgets. After 3 yr of exposure, the 45 trees not grown on lysimeters were harvested, and the plant tissues were weighed. After the fourth growing season, the remaining 45 trees were harvested, and the weight of the plant tissues was determined. Significant effects of ozone or simulated acidic precipitation were not detected, with the exception of a trend for increased needle dry weight with increasing ozone and, in 1990 needles only, with decreasing pH. No effects were detected in total dry weight, aboveground dry weight, coarse or fine root weight, stem dry weight, or relative growth rate. No significant interactions of ozone and pH treatment were detected. Neither ozone nor pH treatment affected the rate of water use by red spruce saplings, even when they were subjected to a dry-down period resulting in drought stress. For. Sci. 43(3):355-361.

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 (LWAt) 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 (Nm), 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, Nm behaved in an entirely different manner, decreasing hyperbolically with LWAt. Since non-structural (carbon in non-structural carbohydrates), and structural (total minus non-structural) needle carbon per dry weight also increased with LWAt, Nm was inversely correlated with both non-structural and structural carbon. Total tree height, increasing significantly LWAt, 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.

Responses of loblolly pine to ozone and simulated acidic rain

Acidic rain and ozone (O3) may have serious consequences on the growth and development of loblolly pine (Pinustaeda L.), a tree species of major economic importance in the southeastern United States. In two independent studies, seedlings of open-pollinated families of loblolly pine were exposed to five concentrations of O3 (0, 80, 160, 240, or 320 nL•L−1) and three simulated rain acidities (pH 5.3, 4.3, or 3.3). Following 23 weeks of growth (12 weeks in charcoal-filtered air and 11 weeks of O3 and simulated acidic rain exposures), stem height, secondary needle dry weight, top and total seedling dry weight, and root/shoot dry weight ratio all were related negatively and linearly with O3 concentration. Stem diameter and root dry weight were also suppressed by O3. Suppression of the growth parameters ranged from 14 to 35% for the greatest O3 concentration. Acidity of simulated rain did not affect seedlings, nor did it affect seedling responses to O3. Results indicate that acid rain probably has little effect on growth of loblolly pine seedlings, but O3 can suppress growth to varying degrees depending on family.

Genetic Parameter Estimates for Seedling Dry Weight Traits and Their Relationship with Parental Breeding Values in Slash Pine

Abstract Seedlings from 64 open-pollinated families of slash pine were grown in low and high nitrogen (N) treatments (5 ppm and 50 ppm) in raised outdoor boxes. Destructive harvests were conducted 3, 6, and 10 mo after sowing to measure dry weights of needles, stems, tap roots, and lateral roots. Genetic parameters (i.e., family-mean heritabilities, Type A genetic correlations, and Type B genetic correlations) were estimated for dry weight traits at each destructive harvest. Family-mean heritability estimates were high for traits in all harvests (most exceeded 0.60). Type A genetic correlation estimates, measuring the commonality of gene effects between two traits measured in the same individuals (i.e., in the same N treatment), were not significantly different from + 1 for most dry weight traits at each harvest. Type B genetic correlation estimates, measuring the commonality of gene effects between two traits measured in different individuals of the same families (i.e., across the two N treatments), were also near + 1 for most traits. Genophenotypic correlations (a single-trait prediction index) between family means of seedling dry weight traits and parental additive genetic breeding values for 15-yr field volume growth were relatively high at the 3-mo measurement (mostly higher than 0.40), but the values were lower for the 6- and 10-mo measurements. Because most pairs of dry weight traits from the same harvest were highly genetically correlated with each other, correlations between field breeding values and those predicted from two-trait indices were only slightly higher than single-trait indices. However, when traits were combined across the three harvest dates, correlations between field breeding values and predictions from two-trait indices increased to over 0.50. The best early selection indices were more effective at identifying the bottom-ranked families than the top-ranked families. An early selection technique using these traits would not be efficient enough to supplant long-term field testing, but could be used to reduce the size of field tests via early culling of poor-performing families or to screen infusion candidates for minimal breeding value requirements. For. Sci. 41(3):546-563.

Effects of light availability and tree size on the architecture of assimilative surface in the canopy of Picea abies: variation in needle morphology.

Needle dimensions, needle surface area, needle dry weight per area (LWA) and needle density (ND, needle weight per volume) were measured in terminal current-year shoots in a natural canopy of variably sized Picea abies (L.) Karst. trees growing along a light gradient. Needle shape was described as a rhomboid. Needle width (D(2)) increased with increasing diffuse site factor, a(d) (relative amount of penetrating diffuse solar radiation), whereas needle thickness (D(1)) remained nearly constant, resulting in an inverse relationship between D(1)/D(2) and a(d) and an increase in the ratio of total (TLA) to projected needle surface area (PLA) with increasing a(d). Because of the variations in needle morphology with respect to light availability, the shoot parameters used in present canopy models are also expected to be light-sensitive, and studies involving shoot morphology should also consider the variability in needle geometry. Needle dimensions and total tree height were not correlated. However, LWA increase with both increasing a(d) and total tree height. When LWA was expressed as the product of ND and needle height (NH, height of the rhomboidal transverse section of a needle), LWA appeared to increase with irradiance, because of changing NH, and with total tree height, because of changing needle density.

Exposure of red spruce seedlings to acid mist: importance of droplet composition just prior to drying periods.

Two-year-old red spruce (Picea rubens Sarg.), raised from seed collected at five locations from Maine to North Carolina, were exposed in a greenhouse to either sulphuric or nitric acid mist (median pH 2-85). Exposures were performed three times a day, four days a week over an eleven-week period during the growing season. Each exposure consisted of 4 h of misting followed by a 3.75 h drying period. Immediately before each drying period, acidic droplets were either left to dry directly on the foliage or were removed by a 15 min deionized water (diw) rinse. When sulphuric acid droplets dried directly on the foliage, visible injury developed and to a lesser degree the same was true for nitric acid. When acidic droplets were replaced with dim before each drying period, foliar injury did not develop despite misting for hundreds of hours at pH values well within the range that has caused visible injury in previous experiments. When acidic droplets dried directly on foliage, needle dry weight was reduced, but differences between sulphuric and nitric acid exposure were not found. No treatment effects were found on terminal shoot length. Treatment responses among seedlings from different seed resources were similar, with greater variation found within provenances than between provenances. We conclude that the composition of liquid on foliage at the end of wet deposition events and the processes occurring during drying periods are important factors in determining the response of red spruce to acidic cloudwater.

Effects of acid rain on growth and nutrient concentrations in Scots pine and Norway spruce seedlings grown in a nutrient-rich soil

The effects of artificially applied acid precipitation on growth and nutrient concentrations of Scots pine ( Pinus sylvestris L.) and Norway spruce ( Picea abies [L.] Karst.) seedlings were investigated in a long-term acid irrigation experiment in field conditions. Seedlings of northern and southern origin were planted in boxes containing peat and composted soil rich in nutrients, and sprinkler irrigated with water acidified with nitric and sulphuric acids to pH 3 or pH 4 for periods varying from two to three and a half growing seasons during 1986–1989. Water irrigated (pH 5.4–7.6) and non-irrigated groups of seedlings were also included in the experiment. At the end of the experiment needles, main and lateral shoots and roots were collected from the seedlings for the determination of height growth and biomass partitioning, and for the analysis of S, N, Mg, P, K, Ca, Mn and Fe concentrations. The treatment effects compared to the irrigated control were studied using multivariate analyses of variance and covariance. In the pine seedlings the total dry matter production increased by 25–70% compared with the irrigated controls when the total wet deposition to the seedlings exceeded 67 kg S ha −1 and 36 kg N ha −1 (e.g. after two growing seasons' exposure of the pH 3 treatment). The increase was mainly due to an increase in needle dry weight (54–72% greater at pH 3) and root weight (20–65% greater at pH 3), whereas the height growth or shoot weight growth were less affected. The northern provenance pine seedlings responded more clearly to the pH 3 irrigation than the southern ones. The treatments had no consistent effects on any of the growth variables studied in the spruce seedlings, however. The pines had higher root and foliage Ca concentrations as a result of the acid irrigation, whereas in spruce, acid rain decreased the Ca concentration in needles and shoots. Root Mn and Fe concentrations were higher in both species as a result of the pH 3 treatment. A higher soil conductivity and Ca concentration resulted from the prolonged pH 3 treatment. The results strongly support the hypothesis that the long-term growth and nutrient allocation response of conifers to acid precipitation is dependent both on the tree species and on the nutritional status of the soil.

Apoplastic Peroxidases and Lignification in Needles of Norway Spruce (Picea abies L.).

The objective of the present study was to investigate the correlation of soluble apoplastic peroxidase activity with lignification in needles of field-grown Norway spruce (Picea abies L.) trees. Apoplastic peroxidases (EC 1.11.1.7) were obtained by vacuum infiltration of needles. The lignin content of isolated cell walls was determined by the acetyl bromide method. Accumulation of lignin and seasonal variations of apoplastic peroxidase activities were studied in the first year of needle development. The major phase of lignification started after bud break and was terminated about 4 weeks later. This phase correlated with a transient increase in apoplastic guaiacol and coniferyl alcohol peroxidase activity. NADH oxidase activity, which is thought to sustain peroxidase activity by production of H2O2, peaked sharply after bud break and decreased during the lignification period. Histochemical localization of peroxidase with guaiacol indicated that high activities were present in lignifying cell walls. In mature needles, lignin was localized in walls of most needle tissues including mesophyll cells, and corresponded to 80 to 130 [mu]mol lignin monomers/g needle dry weight. Isoelectric focusing of apoplastic washing fluids and activity staining with guaiacol showed the presence of strongly alkaline peroxidases (isoelectric point [greater than or equal to] 9) in all developmental stages investigated. New isozymes with isoelectric points of 7.1 and 8.1 appeared during the major phase of lignification. These isozymes disappeared after lignification was terminated. A strong increase in peroxidase activity in autumn was associated with the appearance of acidic peroxidases (isoelectric point [less than or equal to] 3). These results suggest that soluble alkaline apoplastic peroxidases participate in lignin formation. Soluble acidic apoplastic peroxidases were apparently unrelated to developmentally regulated lignification in spruce needles.

Elemental sulphur (S8) in higher plants — biogenic or anthropogenic origin

In the course of investigating lipophilic air pollutants in the epicuticular wax ofPinus sylvestris L. needles, elemental sulphur, S8, was found in all samples. An investigation was conducted to determined the origin of this substance. No correlation between the level of S8 in the needles and human activities in the sampling area could be found, contrary to what would have been expected of an anthropogenic compound. The internal lipids ofP. sylvestris as well as the epicuticular wax of historical herbarium material and seedlings grown in clean, filtered air, and the epicuticular wax of several other species, both gymnosperms and angiosperms, also contained S8. Quantitation of S8 inP. sylvestris gave levels of 7.2±2.9 μg/g wax, 3.8±1.9 μg/g internal lipid and 0.43±0.17 μg/g total needle dry weight. Almost 0.1% of the total sulphur in pine needles is S8, and approximately half of the total S8 is found in the wax. The results suggest that S8 is endogenous in many higher plants. A function for S8 as part of an antifungal defence system is possible.

Interaction of ozone exposure and Fusarium subglutinans inoculation on growth and disease development of loblolly pine seedlings

Seedlings from ten half-sib families of loblolly pine ( Pinus taeda) were exposed in open-top chambers to carbon-filtered air (CF), non-filtered air (NF), or air amended with ozone to 1·7 or 2·5 times ambient. After 105 days of exposure, half the seedlings within each family were wounded but not inoculated and half were wounded and inoculated with the pitch canker fungus, Fusarium subglutinans, to which five families were relatively resistant. After an additional 50 days of ozone treatment, seedling growth and canker development were recorded. Cankers were significantly ( σ ≤ 0·05) smaller among resistant compared to susceptible families, and were significantly larger among seedlings receiving the highest (2·5) compared to the ambient (NF) ozone treatment. The wound scars of non-inoculated seedlings were also significantly larger among seedlings receiving the 2·5 compared to the NF treatment, but these dimensions did not differ significantly with seedling family or resistance. The weights of needles and large roots were significantly smaller at the 2·5 compared to the 1·7 ozone treatment for inoculated but not for non-inoculated seedlings; this resulted in a significant interaction for ozone and inoculation effects. Among resistant families, root weights were significantly smaller for inoculated seedlings. Diameter growth and dry weights of needles were significantly smaller among inoculated compared to non-inoculated seedlings, but did not differ between NF and 2·5 ozone treatments.

Nitrogen uptake, partitioning and internal cycling in Picea sitchensis (Bong.) Carr. as influenced by nitrogen supply.

Four-year-old seedlings of Picea sitchensis (Bong.) Carr. were grown in sand culture throughout 1989 and irrigated with nutrient solutions containing either 1.0 mol N m-3 (Low N) or 6.0 mol N m-3 (High N), to precondition their growth and capacity for N storage. During 1990 N enriched with 15 N was supplied, either from 15 March to 27 June, or 28 June to 20 November. Recovery of unlabelled N was used to determine the storage and immobilization of N for foliage growth, and the partitioning of labelled N taken up during the two periods was measured. Initial growth of trees in 1990 was unaffected by the current N supply and determined only by the N supplied the previous year. High N throughout increased the number of needles grown in 1990 compared to low N-treated trees, but had little effect on the dry weight of individual needles. When preconditioned with High N, trees responded to Low N in 1990 by a reduction in needle dry weight, without altering the number of needles produced. Low N trees supplied with High N in 1990 responded by increasing both needle numbers and dry weight, compared with trees supplied with Low N throughout. The amount of unlabelled N remobilized to foliage growth in 1990 was unaffected by the current N supply but reflected the amount of N in store, as determined by the N supply the previous year. The majority of N was remobilized from the 1989 foliage and none from roots. Partitioning of labelled N taken up during 1990 altered during the year, with a greater proportion of N taken up after 28 June recovered in the roots in all treatments, due to root growth as opposed to allocation of N to storage during the autumn, since root N concentrations fell between 17 June and the final harvest on 20 November.