Does far-red light affect growth and mycorrhizas of Scots pine seedlings grown in forest soil?

We studied the response of Scots pine (Pinus sylvestris L.) to supplementary far-red sidelight in seedlings grown in a forest soil substrate without additional nutrient supply. Our aim was to determine possible changes in the accumulation and allocation of dry weight and mineral nutrients and the presence of mycorrhizas. Half of the seedlings were grown in light conditions simulating reflected far-red light (FR) from neighbouring plants and the other half were controls not receiving additional FR. PAR irradiance was kept constant in both treatments. At the first harvest (41 d of treatment), FR+ had no effect on stem height, biomass accumulation or allocation. However, at the end of the experiment (93 d of treatment), an increase in stem extension rate and stem dry weight was observed in FR+ seedlings when compared to controls. Both control and treated plants had several morphological types of ectomycorrhizas, but no effect of FR+ on the frequency of these morphotypes was observed. Nor was the concentration of ergosterol or estimated mycorrhizal fungal biomass affected. Nutrients were more responsive to the light quality treatment: P concentration in roots and N and P contents in stems and roots were higher in FR+ plants than in control seedlings. These results are in contrast to those of a previous study in which the root system of pine seedlings, which were fertilised and had less developed mycorrhizas, was reduced by FR+. This revised version was published online in June 2006 with corrections to the Cover Date.     

Antioxidant mechanisms of Quercetin and Myricetin in the gas phase and in solution – a comparison and validation of semi-empirical methods

Flavonoids have long been recognized for their general health-promoting properties, of which their antioxidant activity may play an important role. In this work we have studied the properties of two flavonols, quercetin and myricetin, using semi-empirical methods in order to validate the application of the recent Parametric Model 6 and to understand the fundamental difference between the two molecules. Their geometries have been optimized and important molecular properties have been calculated. The energetic of the possible antioxidant mechanisms have also been analyzed. The two studied flavonols do not differ significantly in their molecular properties, but the antioxidant mechanisms by which they may act in solution can be rather different. Moreover, we also show that the Parametric Model 6 can produce reliable information for this type of compounds.     

Fertilization in a mature Scots pine (Pinus sylvestris L.) stand—effects on fine roots

The effects of liquid and solid fertilizers on fine-root development were studied in a 130-year-old Scots pine (Pinus sylvestris L.) stand. Ingrowth cores,viz. initially root-free mesh bags with sieved mineral soil taken outside the plots and driven to a depth of 30 cm from the soil surface, were subsequently resampled and the amount of fine roots was estimated. The total accretion of both fine-root length and dry weight was comparatively high in the liquid fertilization plot. The most substantial net accretion, however, during the 1984 period was in the control plot. The results of the study is that the ramification pattern of the fine roots was strongly influenced by fertilization. The average number of root tips per unit length was 9.9 cm⁻¹ in the control plot cm⁻¹, compared with both the solid (A and B) and liquid fertilization plots (2.3, 3.2 and 3.3 cm⁻¹, respectively) due to a greater occurrence of mycorrhizal aggregates (‘ball mycorrhiza’). The effects of fertilization on the mineral nutrient concentrations in the fine roots were limited—the strongest effects were in the liquid-fertilized area. The observed increase in the concentration of most mineral nutrients in the latter experimental area, however, may be due to a change in the growth pattern of the fine roots rather than an effect of the fertilizers themselves.     

Absorptive root area and stem resistivity in whole trees of contrasting structure and size – improvement of methods

Aims

The study was focused on comparing the results of the three instrumental methods applied simultaneously for root studies in several tree species representing contrasting situations: root systems of different structure and stems of a wide range of diameters (especially when considering their resistivity). We want to learn properties of the methods, make some improvements and test their validity, before they will be applied to a large series of trees at the stand level.

Material and methods

Douglas fir (Pseudotsuga menziessii (Mirbel) Franco) with very asymmetric root system and Blue spruce (Picea pungens Engelm.) with homogeneous root system growing in the Mendel University Training Forest Enterprise in K?tiny, were selected as the main sample trees. Three variants of stem impedance measurements needed for absorptive root area estimates were applied to an additional series of over 20 trees. In order to characterize vertical and circumferential (around stem) root distribution we applied (1) the sap flow radial patterns measured by the multi-point sensors based on the heat field deformation (HFD) method, and (2) a modified earth impedance (MEI) method from the group of thermodynamic and electric measuring methods and finally we (3) almost harmlessly excavated the whole root system by supersonic air stream. Three steps of absorptive root area measurements were improved: (a) Impact of stem impedance was almost eliminated, (b) Excessive variation of stem impedance values measured too close to stems (in a place with the most heterogeneous materials) was compensated by extrapolation of several close points, (c) Impact of high curvature of small stems was determined and eliminated by an equation.

Results

All the methods gave similar results when considering differences between individual trees as well as between stem sides. Sap flow density was interesting when expressed per measured absorptive root area and leaf area. Experimental data of main and additional sample trees confirmed validity of relationship, which can be applied to improve stem resistivity especially in small trees.

Conclusions

Results indicated, that all the instrumental methods are field applicable and suitable for quantitative measurements, when specific properties of the methods and stem macrostructure are taken into account. Soil electric parameters characterize the important properties related to presence of cracks, water content, and ion concentration, which are being analyzed now.     

Assessing soil ecosystem processes – biodiversity relationships in a nature reserve in Central Europe

Plant and Soil - Plant diversity – ecosystem processes relationships are essential to our understanding of ecosystem functioning. We aimed at disentangling the nature of such relationships in...     

Exploration type-specific standard values of extramatrical mycelium – a step towards quantifying ectomycorrhizal space occupation and biomass in natural soil

The present study aims at providing standard values for the exploration type (ET)-specific quantification of extramatrical mycelium (EMM) of ectomycorrhizal fungi applicable to ecological field studies. These values were established from mycelial systems of ectomycorrhizae (ECM) synthesized in rhizotrons with near-to-natural peat substrate. Based on image analysis, the “Specific Potential Mycelial Space Occupation” (sPMSO), i.e. the ET-specific complete area that is covered by the EMM systems (mm² cm⁻¹ ECM⁻¹), and the “Specific Actual Mycelial Space Occupation” (sAMSO), i.e. the projection area of mycelial systems (mm² cm⁻¹ ECM⁻¹), were analyzed as an extension of a previously described approach. The “Specific Extramatrical Mycelial Length” (sEML) [m cm⁻¹ ECM⁻¹] and the “Specific Extramatrical Mycelial Biomass” (sEMB) (μg cm⁻¹ ECM⁻¹) were calculated for each of the ET via the proportion of hyphal projected area, hyphal length and biomass, the latter two being derived from previous measurements on Piloderma croceum, a “Medium-Distance” (MD)-ET. Both sPMSO and sAMSO were highest for the “Long-Distance” (LD)-ET, whereas those of the “Short-Distance” (SD)-ET and MD-ET were similar, although showing high variation. In contrast, mycelial density per occupied area of the MD-ET was twice as high as that of the LD-ET. Proportional to the sAMSO, the EMM length and biomass differed considerably between the three ET with values of the MD-ET being 1.9 times higher than those of SD-ET, and those of the LD-ET being 15 times higher than those of the SD-ET. These standards in relation to ECM length may ease quantification of mycelial space occupation and biomass in a relatively simple way. Thereby, the ET-specific contribution of EMM can be distinguished—also of non-cultivable species—and up-scaling to large-scale estimation of cost/benefit relations is possible.     

Mixed leaf litter effects on decomposition rates and soil microarthropod communities in an oak–pine stand in Japan

Rates of decomposition, and soil faunal abundance and diversity associated with single-species and mixed-species litters were studied in a litter bag experiment in an oak–pine forest. We used two canopy species of leaf litter, pine and oak, and one shrub species, Sasa, and compared decomposition rates, and soil microarthropod abundance and community structure of oribatid mites in the litter bags. Mass loss of single species decreased in the order: oak > pine > Sasa. While the total mass loss rates of mixed litter were intermediate between those of the constituent species, enhancement of mass loss from the three-species mixture and from mixed slow-decomposing litters (pine and Sasa) was observed. Faunal abundance in litter bags was higher in mixed-species litter than in those with single-species litter, and species richness of oribatid mites was also higher in the three-species mixed litter. Faunal abundance in single-species litter bags was not correlated with mass loss, although enhancement of mass loss in mixed litter bags corresponded with higher microarthropod abundance. Habitat heterogeneity in mixed litter bags seemed to be responsible for the more abundant soil microarthropod community.     

Structure,ecology and physiology of root clusters – a review

Hairy rootlets, aggregated in longitudinal rows to form distinct clusters, are a major part of the root system in some species. These root clusters are almost universal (1600 species) in the family Proteaceae (proteoid roots), with fewer species in another seven families. There may be 10–1000 rootlets per cm length of parent root in 2–7 rows. Proteoid roots may increase the surface area by over 140× and soil volume explored by 300× that per length of an equivalent non-proteoid root. This greatly enhances exudation of carboxylates, phenolics and water, solubilisation of mineral and organic nutrients and uptake of inorganic nutrients, amino acids and water per unit root mass. Root cluster production peaks at soil nutrient levels (P, N, Fe) suboptimal for growth of the rest of the root system, and may cease when shoot mass peaks. As with other root types, root cluster production is controlled by the interplay between external and internal nutrient levels, and mediated by auxin and other hormones to which the process is particularly sensitive. Proteoid roots are concentrated in the humus-rich surface soil horizons, by 800× in Banksia scrub-heath. Compared with an equal mass of the B horizon, the A₁ horizon has much higher levels of N, P, K and Ca in soils where species with proteoid root clusters are prominent, and the concentration of root clusters in that region ensures that uptake is optimal where supply is maximal. Both proteoid and non-proteoid root growth are promoted wherever the humus-rich layer is located in the soil profile, with 4× more proteoid roots per root length in Hakea laurina. Proteoid root production near the soil surface is favoured among hakeas, even in uniform soil, but to a lesser extent, while addition of dilute N or P solutions in split-root system studies promotes non-proteoid, but inhibits proteoid, root production. Local or seasonal applications of water to hakeas initiate non-proteoid, then proteoid, root production, while waterlogging inhibits non-proteoid, but promotes proteoid, root production near the soil surface. A chemical stimulus, probably of bacterial origin, may be associated with root cluster initiation, but most experiments have alternative interpretations. It is possible that the bacterial component of soil pockets rich in organic matter, rather than their nutrient component, could be responsible for the proliferation of proteoid roots there, but much more research on root cluster microbiology is needed.     

Does timing of boron application affect needle and bud structure in Scots pine and Norway spruce seedlings?

Loss of apical dominance is a well-known boron (B) deficiency symptom in trees. Recent field studies indicate that B deficiency may cause irreversible damage in emerging leader buds leading to bushy growth, and changes in developing needles in mature Norway spruce trees. We experimentally studied if timing of B application affects needles and buds of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) seedlings with low initial B levels. The treatments were: no B (B0); B supply from the beginning of the simulated summer (B1); starting soon after bud burst (B2) and starting at the occurrence of first needle primordia in new spruce buds (B3). At the end of the experiment, B concentration in B1 was 23 mg kg⁻¹ (pine) or 17 mg kg⁻¹ (spruce) and lower in the later applications. In B0 it was at deficiency limit. In B0, B2 and B3, there were fewer sclerenchyma cells, and cavities occurred in vascular cylinders in pine needles, and in spruce buds there were more tanniferous cells in the primordial shoots compared to B1. Furthermore, in all but B1 there was cell collapse in the bud apex of some spruce seedlings. The experimentally induced changes were the same as earlier reported in B deficient conifers in the field, and indicate, similarly as in the field that adequate B is necessary throughout the growing season for healthy growth, particularly for spruce. The differences between spruce and pines are due, at least partly, to the differences in time frame of needle development and in the differences in development of conducting tissues in the buds.     

Biomass of extramatrical ectomycorrhizal mycelium and fine roots in a young Norway spruce stand — a study using ingrowth bags with different substrates

Background and aims

The partitioning of below ground carbon inputs into roots and extramatrical ectomycorrhizal mycelium (ECM) is crucial for the C cycle in forest soils. Here we studied simultaneously the newly grown biomass of ECM and fine roots in a young Norway spruce stand.

Methods

Ingrowth mesh bags of 16 cm diameter and 12 cm height were placed in the upper soil and left for 12 to 16 months. The 2 mm mesh size allowed the ingrowth of fungal hyphae and roots whereas a 45 μm mesh size allowed only the ingrowth of hyphae. The mesh bags were filled with either EA horizon soil, pure quartz sand or crushed granite. Controls without any ingrowth were established for each substrate by solid tubes (2010) and by 1 μm mesh bags (2011). The fungal biomass in the substrates was estimated by the PLFA 18:2ω6,9 and ECM biomass was calculated as difference between fungal biomass in mesh bags and controls.

Results

The maximum ECM biomass was 438 kg ha^?1 in October 2010 in 2 mm mesh bags with EA substrate, and the minimum was close to zero in 2011 in 45 μm mesh bags with quartz sand. The high P content of the crushed granite did not influence the ECM biomass. Fine root biomass reached a maximum of 2,343 kg ha^?1 in October 2010 in mesh bags with quartz sand after 16 months exposure. In quartz sand and crushed granite, ECM biomass correlated positively with fine root biomass and the number of root tips, and negatively with specific root length.

Conclusion

The ratio of ECM biomass/fine root biomass in October ranged from 0.1 to 0.3 in quartz sand and crushed granite, but from 0.7 to 1.8 in the EA substrate. The results for the EA substrate suggest a large C flux to ECM under field conditions.     

Starch determination in Chlorella vulgaris—a comparison between acid and enzymatic methods

Different methods for estimating starch in Chlorella vulgaris were compared with the view of establishing a procedure suitable for rapid and accurate determination of starch content in this microalgal species. A close agreement was observed between methods that use perchloric acid and enzymatic methods that use α-amylase and amyloglucosidase to hydrolyze the starch of microalgae grown under different nitrogen culture conditions. Starch values obtained by these methods were significantly higher than those estimated by using hydrochloric acid as solubilizing and hydrolyzing agent. The enzymatic method (EM1) proved to be the most rapid and precise method for microalgal starch quantification. Furthermore, the evaluation of resistant starch by enzymatic methods assayed in nitrogen-sufficient and nitrogen-starved cells showed that no formation of this type of starch occurred in microalgae, meaning that this should not interfere with starch content determinations.     

Development of needle retention in Scots pine (Pinus sylvestris) in 1957–1991 in northern and southern Finland

The needle trace method was used to study retrospectively the long-term latitudinal variation in needle retention in Scots pine (Pinus sylvestris L.) in Finland. The mean annual summer needle retention (ANR) along the main stem varied from 3.4 to 6.0 needle sets during the period 1957–1991. The lowest values were observed in southern and the highest in northern Finland. The length of the growing season, expressed as the thermal sum (threshold value +5 °C), was negatively correlated with the mean ANR (r=-0.96). The geographical needle retention pattern (NRP) for the period 1957–1991 showed a clearly increasing trend from 1957 to 1969 (southern Finland) and to 1975 (northern Finland); thereafter, the NRP tended to decrease close to its minimum value recorded in 1991. The general level of the NRP was approximately 5.0 needle sets in northern Finland and 3.5–4.0 needle sets in southern Finland. The NRP, with its 6–12 year cycle for southern Finland, was clearly periodical. Differences in the NRP among the ten stands in southern Finland were small, whereas the said periodicity was missing and the differences were high among the stands in northern Finland. The results indicate that variation in the number of needle sets, viz. defoliation of pines, is a normal phenomenon. The role of net carbon assimilation as a regulator of the number of needle sets is discussed.     

Plant hydraulic lift of soil water – implications for crop production and land restoration

Zinc deficiency is a well-documented problem in food crops, causing decreased crop yields and nutritional quality. Generally, the regions in the world with Zn-deficient soils are also characterized by widespread Zn deficiency in humans. Recent estimates indicate that nearly half of world population suffers from Zn deficiency. Cereal crops play an important role in satisfying daily calorie intake in developing world, but they are inherently very low in Zn concentrations in grain, particularly when grown on Zn-deficient soils. The reliance on cereal-based diets may induce Zn deficiency-related health problems in humans, such as impairments in physical development, immune system and brain function. Among the strategies being discussed as major solution to Zn deficiency, plant breeding strategy (e.g., genetic biofortification) appears to be a most sustainable and cost-effective approach useful in improving Zn concentrations in grain. The breeding approach is, however, a long-term process requiring a substantial effort and resources. A successful breeding program for biofortifying food crops with Zn is very much dependent on the size of plant-available Zn pools in soil. In most parts of the cereal-growing areas, soils have, however, a variety of chemical and physical problems that significantly reduce availability of Zn to plant roots. Hence, the genetic capacity of the newly developed (biofortified) cultivars to absorb sufficient amount of Zn from soil and accumulate it in the grain may not be expressed to the full extent. It is, therefore, essential to have a short-term approach to improve Zn concentration in cereal grains. Application of Zn fertilizers or Zn-enriched NPK fertilizers (e.g., agronomic biofortification) offers a rapid solution to the problem, and represents useful complementary approach to on-going breeding programs. There is increasing evidence showing that foliar or combined soil+foliar application of Zn fertilizers under field conditions are highly effective and very practical way to maximize uptake and accumulation of Zn in whole wheat grain, raising concentration up to 60 mg Zn kg⁻¹. Zinc-enriched grains are also of great importance for crop productivity resulting in better seedling vigor, denser stands and higher stress tolerance on potentially Zn-deficient soils. Agronomic biofortification strategy appears to be essential in keeping sufficient amount of available Zn in soil solution and maintaining adequate Zn transport to the seeds during reproductive growth stage. Finally, agronomic biofortification is required for optimizing and ensuring the success of genetic biofortification of cereal grains with Zn. In case of greater bioavailability of the grain Zn derived from foliar applications than from soil, agronomic biofortification would be a very attractive and useful strategy in solving Zn deficiency-related health problems globally and effectively.     

Standardisation of data from real-time quantitative PCR methods – evaluation of outliers and comparison of calibration curves

Background  

As real-time quantitative PCR (RT-QPCR) is increasingly being relied upon for the enforcement of legislation and regulations dependent upon the trace detection of DNA, focus has increased on the quality issues related to the technique. Recent work has focused on the identification of factors that contribute towards significant measurement uncertainty in the real-time quantitative PCR technique, through investigation of the experimental design and operating procedure. However, measurement uncertainty contributions made during the data analysis procedure have not been studied in detail. This paper presents two additional approaches for standardising data analysis through the novel application of statistical methods to RT-QPCR, in order to minimise potential uncertainty in results.     

Impact of soil salinity on the plant-growth – promoting and biological control abilities of root associated bacteria

The effectiveness of plant growth – promoting bacteria is variable under different biotic and abiotic conditions. Abiotic factors may negatively affect the beneficial properties and efficiency of the introduced PGPR inoculants. The aim of this study was to evaluate the effect of plant growth – promoting rhizobacteria on plant growth and on the control of foot and root rot of tomatoes caused by Fusarium solani under different soil salinity conditions. Among the five tested strains, only Pseudomonas chlororaphis TSAU13, and Pseudomonas extremorientalis TSAU20 were able to stimulate plant growth and act as biological controls of foot and root rot disease of tomato. The soil salinity did not negatively affect the beneficial impacts of these strains, as they were able to colonize and survive on the roots of tomato plants under both saline and non-saline soil conditions. The improved plant height and fruit yield of tomato was also observed for plants inoculated with P. extremorientalis TSAU20. Our results indicated that, saline condition is not crucial factor in obtaining good performance with respect to the plant growth stimulating and biocontrol abilities of PGPR strains. The bacterial inoculant also enhanced antioxidant enzymes activities thereby preventing ROS induced oxidative damage in plants, and the proline concentrations in plant tissue that play an important role in plant stress tolerance.     

Growth and hyoscyamine production of ‘hairy root’ cultures of Datura stramonium in a modified stirred tank reactor

Summary The growth and hyoscyamine production of transformed roots of Datura stramonium have been examined in a modified 14-1 stirred tank reactor in both batch and continuous fermentations on media containing half or full strength Gamborg's B5 salts and at three different temperatures. Under a range of conditions, roots grown on half strength B5 salts with 3% w/v sucrose had a higher dry matter content (up to 8.3% w/w) and a higher hyoscyamine content (up to 0.52 mg·g^–1 wet weight) than roots grown on full strength B5 salts with the same level of sucrose (up to 4.6% w/w dry matter and up to 0.33 mg hyoscyamine g^–1 wet weight). Growth at 30°C was initially faster than at either 25°C or 35°C and by day 12, the drained weight of roots in the fermentor at 30°C was about fourfold greater than at 25°C and twice that at 35°C. The ultimate hyoscyamine levels attained (approximately 0.5 mg·g^–1 wet weight) were similar at both 25°C and 30°C but some 40% lower at 35°C. Final packing densities of 70% w/v were achieved for roots after 37 days growth at 25°C and the highest production rate of 8.2 mg hyoscyamine l^–1 per day was obtained for roots grown at 30°C. In continuous fermentation at 25°C, the release of hyoscyamine into the culture medium was low (less than 0.5% w/w of the total) but was up to sevenfold higher in fermentors operated at 30°C or 35°C. Offprint requests to: M. G. Hilton     

Effectiveness and recovery action of a perturbation balance test – a comparison of single-leg and bipedal stances

Abstract

Dynamic balancing abilities can be assessed with perturbation tests. The present study examined the effectiveness of balancing (damping ratio) and the recovery action (directional ratio) in bipedal and dominant single-leg stance in the young population. Twenty-four healthy young adult participants completed unidirectional lateral perturbations successfully using a Posturomed© platform (Haider Bioswing, Germany). Single-leg stances had similar damping scores (p?=?0.551) to and lower directional ratio values (p?=?0.002) than bipedal recoveries. This shows that different recovery actions can achieve similar effectiveness in the two stances. A test evaluation methodology that simultaneously utilises performance and motion characteristic parameters was demonstrated.     

Turnover of “new” and “old” carbon in soil microbial biomass

The contributions of “new” carbon coming from plants with the C4-type of photosynthesis (maize) and “old” carbon from soil organic matter (SOM) formed under C3 vegetation as carbon sources for microorganisms was determined. Soil samples were taken from the plots of field experiments on Chernozem and Phaeozem. The values of δ¹³C were determined in evolved CO₂, SOM, total microbial biomass (C_mic), and phospholipid fatty acids (PLFA), assuming that the PLFA markers for certain taxonomic groups of microorganisms enriched in C4 carbon indicated a more significant role of these microorganisms in the transformation of root exudates and plant residues. Carbon pools were arranged in the following order by the degree of their enrichment with “new” C: SOM < C_mic < CO₂. Consequently, the “new” carbon proved to be a more preferable substrate for microbial growth than the “old” one. The share of C4 in the markers varied from 18 to 60% (on average 38%) in Phaeozem and from 15 to 40% in Chernozem (on average 28%). The groups of microorganisms in Phaeozem were arranged in the following order by the degree of their enrichment with “new” carbon: protozoa < saprotrophic fungi < actinomycetes < gram-positive bacteria < gramnegative bacteria < mycorrhizal fungi. In Chernozem, the contribution of C4 to the carbon composition of PLFA did not differ significantly for various groups of microorganisms. The C4 content within the PLFA markers of fungi and gram-negative bacteria did not demonstrate any crucial contribution of these groups of organisms to the transformation of “new” C. The long-term C3–C4 transition probably results in formation of a broad range of carbon pools similar in their C4 content but different in resistance to mineralization; therefore, gram-positive bacteria could assimilate C4 from resistant C pools. The low content of “new” carbon in the PLFA markers of fungi may be explained by a considerable portion of dormant forms.     

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