Antibacterial and Oxidative Stress-Protective Effects of Five Monoterpenes from Softwood

Volatile organic compounds (VOC) affect the quality of indoor air. Terpenes and especially monoterpenes are the main molecules emitted from softwood material (coniferous species), which is widely used in construction. The corneal epithelium is one of the first human membranes to encounter VOCs in the air. Moreover, the industrial use of pleasant-scented monoterpenes in cosmetics, food, and detergents exposes people to monoterpenes in their daily lives. In the present study, the health effective properties of five monoterpenes from softwood were tested; cytotoxicity and oxidative stress-protective effects of α- and β-pinenes, R- and S-limonene, and 3-carene were tested in a human corneal epithelial (HCE) cell model system and with two additional in vitro antioxidant tests: oxygen radical absorbance capacity (ORAC) and hydrogen peroxide (H₂O₂) scavenging. Antibacterial efficacies were tested with two bioluminescent bacterial biosensor strains (Escherichia coli K12+pcGLS11 and Staphylococcus aureus RN4220+pAT19) and with minimum inhibitory concentration (MIC) test against Escherichia coli. Only very high concentrations of monoterpenes (0.3–0.5 mg/mL) demonstrated cytotoxicity against HCE cells. Contrary to the original hypothesis, monoterpenes did not exhibit strong antioxidant properties in tested concentrations. However, biosensors and MIC tests indicated clear antibacterial activities for all tested monoterpenes.

Salix spp. Bark Hot Water Extracts Show Antiviral, Antibacterial, and Antioxidant Activities-The Bioactive Properties of 16 Clones

Earlier studies have shown that the bark of Salix L. species (Salicaceae family) is rich in extractives, such as diverse bioactive phenolic compounds. However, we lack knowledge on the bioactive properties of the bark of willow species and clones adapted to the harsh climate conditions of the cool temperate zone. Therefore, the present study aimed to obtain information on the functional profiles of northern willow clones for the use of value-added bioactive solutions. Of the 16 willow clones studied here, 12 were examples of widely distributed native Finnish willow species, including dark-leaved willow (S. myrsinifolia Salisb.) and tea-leaved willow (S. phylicifolia L.) (3 + 4 clones, respectively) and their natural and artificial hybrids (3 + 2 clones, respectively). The four remaining clones were commercial willow varieties from the Swedish willow breeding program. Hot water extraction of bark under mild conditions was carried out. Bioactivity assays were used to screen antiviral, antibacterial, antifungal, yeasticidal, and antioxidant activities, as well as the total phenolic content of the extracts. Additionally, we introduce a fast and less labor-intensive steam-debarking method for Salix spp. feedstocks. Clonal variation was observed in the antioxidant properties of the bark extracts of the 16 Salix spp. clones. High antiviral activity against a non-enveloped enterovirus, coxsackievirus A9, was found, with no marked differences in efficacy between the native clones. All the clones also showed antibacterial activity against Staphylococcus aureus and Escherichia coli, whereas no antifungal (Aspergillus brasiliensis) or yeasticidal (Candida albicans) efficacy was detected. When grouping the clone extract results into Salix myrsinifolia, Salix phylicifolia, native hybrid, artificial hybrid, and commercial clones, there was a significant difference in the activities between S. phylicifolia clone extracts and commercial clone extracts in the favor of S. phylicifolia in the antibacterial and antioxidant tests. In some antioxidant tests, S. phylicifolia clone extracts were also significantly more active than artificial clone extracts. Additionally, S. myrsinifolia clone extracts showed significantly higher activities in some antioxidant tests than commercial clone extracts and artificial clone extracts. Nevertheless, the bark extracts of native Finnish willow clones showed high bioactivity. The obtained knowledge paves the way towards developing high value-added biochemicals and other functional solutions based on willow biorefinery approaches.

Field-Grown and In Vitro Propagated Round-Leaved Sundew (Drosera rotundifolia L.) Show Differences in Metabolic Profiles and Biological Activities

Drosera rotundifolia L. is a carnivorous plant used in traditional medicine for its therapeutic properties. Because of its small size, its collection in nature is laborious and different cultivation methods have been studied to ensure availability. However, only a few studies exist where the lab-grown sundew tissue and field-grown sundew would have been compared in their functionality or metabolic profiles. In this study, the antioxidant and antiviral activities of lab-grown and field-grown sundew extracts and their metabolic profiles are examined. The effect of drying methods on the chromatographic profile of the extracts is also shown. Antioxidant activity was significantly higher (5–6 times) in field-grown sundew but antiviral activity against enterovirus strains coxsackievirus A9 and B3 was similar in higher extract concentrations (cell viability ca. 90%). Metabolic profiles showed that the majority of the identified compounds were the same but field-grown sundew contained higher numbers and amounts of secondary metabolites. Freeze-drying, herbal dryer, and oven or room temperature drying of the extract significantly decreased the metabolite content from −72% up to −100%. Freezing was the best option to preserve the metabolic composition of the sundew extract. In conclusion, when accurately handled, the lab-grown sundew possesses promising antiviral properties, but the secondary metabolite content needs to be higher for it to be considered as a good alternative for the field-grown sundew.

Toxicological and bioactivity evaluation of blackcurrant press cake, sea buckthorn leaves and bark from Scots pine and Norway spruce extracts under a green integrated approach

Aqueous extracts from blackcurrant press cake (BC), Norway spruce bark (NS), Scots pine bark (SP), and sea buckthorn leaves (SB) were obtained using maceration and pressurized hot water and tested for their bioactivities. Maceration provided the extraction of higher dry matter contents, including total phenolics (TPC), anthocyanins, and condensed tannins, which also impacted higher antioxidant activity. NS and SB extracts presented the highest mean values of TPC and antioxidant activity. Individually, NS extract presented high contents of proanthocyanidins, resveratrol, and some phenolic acids. In contrast, SB contained a high concentration of ellagitannins, ellagic acid, and quercetin, explaining the antioxidant activity and antibacterial effects. SP and BC extracts had the lowest TPC and antioxidant activity. However, BC had strong antiviral efficacy, whereas SP can be considered a potential ingredient to inhibit α-amylase. Except for BC, the other extracts decreased reactive oxygen species (ROS) generation in HCT8 and A549 cells. Extracts did not inhibit the production of TNF-alpha in lipopolysaccharide-stimulated THP-1 macrophages but inhibited the ROS generation during the THP-1 cell respiratory burst. The recovery of antioxidant compounds from these by-products is incentivized for high value-added applications.

Stability and Photoisomerization of Stilbenes Isolated from the Bark of Norway Spruce Roots

Stilbenes or stilbenoids, major polyphenolic compounds of the bark of Norway spruce (Picea abies L. Karst), have potential future applications as drugs, preservatives and other functional ingredients due to their antioxidative, antibacterial and antifungal properties. Stilbenes are photosensitive and UV and fluorescent light induce trans to cis isomerisation via intramolecular cyclization. So far, the characterizations of possible new compounds derived from trans-stilbenes under UV light exposure have been mainly tentative based only on UV or MS spectra without utilizing more detailed structural spectroscopy techniques such as NMR. The objective of this work was to study the stability of biologically interesting and readily available stilbenes such as astringin and isorhapontin and their aglucones piceatannol and isorhapontigenin, which have not been studied previously. The effects of fluorescent and UV light and storage on the stability of trans stilbenes were assessed and the identification and characterisation of new compounds formed during our experiments were carried out by chromatographic (HPLC, GC) and spectroscopic techniques (UV, MS, NMR). The stilbenes undergo a trans to cis isomerisation under extended UV irradiation by intramolecular cyclisation (by the formation of a new C-C bond and the loss of two hydrogens) to phenanthrene structures. The characterised compounds are novel and not described previously.

Site fertility and soil water-table level affect fungal biomass production and community composition in boreal peatland forests

A substantial amount of below-ground carbon (C) is suggested to be associated with fungi, which may significantly affect the soil C balance in forested ecosystems. Ergosterol from in-growth mesh bags and litterbags was used to estimate fungal biomass production and community composition in drained peatland forests with differing fertility. Extramatrical mycelia (EMM) biomass production was generally higher in the nutrient-poor site, increased with deeper water table level and decreased along the length of the recovery time. EMM biomass production was of the same magnitude as in mineral-soil forests. Saprotrophic fungal biomass production was higher in the nutrient-rich site. Both ectomycorrhizal (ECM) and saprotrophic fungal community composition changed according to site fertility and water table level. ECM fungal community composition with different exploration types may explain the differences in fungal biomass production between peatland forests. Melanin-rich Hyaloscypha may indicate decreased turnover of biomass in nutrient-rich young peatland forest. Genera Lactarius and Laccaria may be important in nutrient rich and Piloderma in the nutrient-poor conditions, respectively. Furthermore, Paxillus involutus and Cortinarius sp. may be important generalists in all sites and responsible for EMM biomass production during the first summer months. Saprotrophs showed a functionally more diverse fungal community in the nutrient-rich site.

A panel of bioluminescent whole-cell bacterial biosensors for the screening for new antibacterial substances from natural extracts

Whole-cell bacterial biosensors can be applied for the screening of antibacterial properties of extracts. We constructed a biosensor panel consisting of four different bacterial biosensor strains: Escherichia, Staphylococcus, Acinetobacter and Pseudomonas for expanded screening potential. The functionality of the panel was first evaluated with known antibacterial compounds: ethanol, naphthoquinones (juglone, lawsone, plumbagin) and a flavonoid (quercetin). Natural extracts comprise a vast source of potential new antibacterials for diverse functional purposes. To demonstrate the utilization of the panel for screening of a demanding sample material, round-leaved sundew (Drosera rotundifolia) extracts were used as an example. Differences between field- and laboratory originating sundew extracts could be detected. This demonstrates the efficiency of the developed biosensor panel in the rapid screening of the antibacterial properties of plant extracts.

Clonal Variation in the Bark Chemical Properties of Hybrid Aspen: Potential for Added Value Chemicals

This study aims to promote comprehensive utilization of woody biomass by providing a knowledgebase on the utility of aspen bark as a new alternative source for fossil-based chemicals. The research focused on the analysis of clonal variation in: (1) major chemical components, i.e., hemicelluloses, cellulose, and lignin; (2) extraneous materials, i.e., bark extractives, and suberic acid; (3) condensed tannins content and composition; and (4) screening differences in antioxidative properties and total phenolic content of hot water extracts and ethanol-water extracts of hybrid aspen bark. Results of this study, the discovery of clonal variation in utilizable chemicals, pave the way for further research on added-value potential of under-utilized hybrid aspen and its bark. Clonal variation was found in notable part of chemicals with potential for utilization. Based on the results, an appropriate bark raw material can be selected for tailored processing, thus improving the resource efficiency. The results also indicate that by applying cascade processing concepts, bark chemical substances could be more efficiently utilized with more environmentally friendly methods.

Fate of Antioxidative Compounds within Bark during Storage: A Case of Norway Spruce Logs

Softwood bark is an important by-product of forest industry. Currently, bark is under-utilized and mainly directed for energy production, although it can be extracted with hot water to obtain compounds for value-added use. In Norway spruce (Picea abies [L.] Karst.) bark, condensed tannins and stilbene glycosides are among the compounds that comprise majority of the antioxidative extractives. For developing feasible production chain for softwood bark extractives, knowledge on raw material quality is critical. This study examined the fate of spruce bark tannins and stilbenes during storage treatment with two seasonal replications (i.e., during winter and summer). In the experiment, mature logs were harvested and stored outside. During six-month-storage periods, samples were periodically collected for chemical analysis from both inner and outer bark layers. Additionally, bark extractives were analyzed for antioxidative activities by FRAP, ORAC, and H2O2 scavenging assays. According to the results, stilbenes rapidly degraded during storage, whereas tannins were more stable: only 5-7% of the original stilbene amount and ca. 30-50% of the original amount of condensed tannins were found after 24-week-storage. Summer conditions led to the faster modification of bark chemistry than winter conditions. Changes in antioxidative activity were less pronounced than those of analyzed chemical compounds, indicating that the derivatives of the compounds contribute to the antioxidative activity. The results of the assays showed that, on average, ca. 27% of the original antioxidative capacity remained 24 weeks after the onset of the storage treatment, while a large variation (2-95% of the original capacity remaining) was found between assays, seasons, and bark layers. Inner bark preserved its activities longer than outer bark, and intact bark attached to timber is expected to maintain its activities longer than a debarked one. Thus, to ensure prolonged quality, no debarking before storage is suggested: outer bark protects the inner bark, and debarking enhances the degradation.

Bioactive Properties of the Aqueous Extracts of Endophytic Fungi Associated with Scots Pine (Pinus sylvestris) Roots

Despite the continuing interest in various plant and natural products, only a small portion of the biologically active compounds from nature has been discovered and exploited. In this study, antioxidant and antibacterial properties of aqueous fractions of three endophytic fungi isolated from the roots of 8-year-old Scots pines (Pinus sylvestris) growing on a drained peatland were investigated. The endophytic fungi species were Acephala applanata, Phialocephala fortinii, and Humicolopsis cephalosporioides/Coniochaeta mutabilis. The bioactivities were examined using hydrogen peroxide scavenging and oxygen radical absorbance capacity tests as well as sensitive Escherichia coli-based biosensors, which produce a luminescent signal in the presence of substances with oxidative or genotoxic properties. In addition, cell models for Parkinson's disease, age-related macular degeneration, and osteoarthritis were used to evaluate the potential for pharmaceutical applications. The aqueous extracts of fungi and 19 out of 42 fractions were found to be active in one or more of the tests used. However, no activity was found in the age-related macular degeneration and osteoarthritis cell model tests. Additionally, bioactivity data was connected with metabolites putatively annotated, and out of 330 metabolites, 177 were interesting in view of the bioactivities investigated. A majority of these were peptides and all three fungal species shared a highly similar metabolome. We propose that Scots pine endophytic fungi are a rich source of interesting metabolites, and synergistic effects may cause the bioactivities, as they were found to vary after the fractionation process.

Thermospermine Synthase (ACL5) and Diamine Oxidase (DAO) Expression Is Needed for Zygotic Embryogenesis and Vascular Development in Scots Pine

Unlike in flowering plants, the detailed roles of the enzymes in the polyamine (PA) pathway in conifers are poorly known. We explored the sequence conservation of the PA biosynthetic genes and diamine oxidase (DAO) in conifers and flowering plants to reveal the potential functional diversification of the enzymes between the plant lineages. The expression of the genes showing different selective constraints was studied in Scots pine zygotic embryogenesis and early seedling development. We found that the arginine decarboxylase pathway is strongly preferred in putrescine production in the Scots pine as well as generally in conifers and that the reduced use of ornithine decarboxylase (ODC) has led to relaxed purifying selection in ODC genes. Thermospermine synthase (ACL5) genes evolve under strong purifying selection in conifers and the DAO gene is also highly conserved in pines. In developing Scots pine seeds, the expression of both ACL5 and DAO increased as embryogenesis proceeded. Strong ACL5 expression was present in the procambial cells of the embryo and in the megagametophyte cells destined to die via morphologically necrotic cell death. Thus, the high sequence conservation of ACL5 genes in conifers may indicate the necessity of ACL5 for both embryogenesis and vascular development. Moreover, the result suggests the involvement of ACL5 in morphologically necrotic cell death and supports the view of the genetic regulation of necrosis in Scots pine embryogenesis and in plant development. DAO transcripts were located close to the cell walls and between the walls of adjacent cells in Scots pine zygotic embryos and in the roots of young seedlings. We propose that DAO, in addition to the role in Put oxidation for providing H2O2 during the cell-wall structural processes, may also participate in cell-to-cell communication at the mRNA level. To conclude, our findings indicate that the PA pathway of Scots pines possesses several special functional characteristics which differ from those of flowering plants.

The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids

Suberin fatty acids were extracted from outer bark of Silver birch (Betula pendula Roth.) using an isopropanolic sodium hydroxide solution. Laboratory sheets composed of lignocellulosic fiber networks were prepared from unbleached and unrefined softwood kraft pulp and further impregnated with suberin fatty acid monomers and cured with maleic anhydride in ethanol solution. The treatment resulted in hydrophobic surfaces, in which the contact angles remained over 120 degrees during the entire measurement. The fiber network also retained its water vapor permeability and enhanced fiber–fiber bonding resulted in improved tensile strength of the sheets. Scanning electron microscopy (SEM) images revealed that the curing agent, together with suberin fatty acids, was evenly distributed on the fiber surfaces and smoothing occurred over the wrinkled microfibrillar structure. High concentrations of the curing agent resulted in globular structures containing betulinol derivates as revealed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Also, the larger amount of suberin fatty acid monomers slightly impaired the optical properties of sheets.

Metabolic Profiling of Water-Soluble Compounds from the Extracts of Dark Septate Endophytic Fungi (DSE) Isolated from Scots Pine (Pinus sylvestris L.) Seedlings Using UPLC-Orbitrap-MS

Endophytes are microorganisms living inside plant hosts and are known to be beneficial for the host plant vitality. In this study, we isolated three endophytic fungus species from the roots of Scots pine seedlings growing on Finnish drained peatland setting. The isolated fungi belonged to dark septate endophytes (DSE). The metabolic profiles of the hot water extracts of the fungi were investigated using Ultrahigh Performance Liquid Chromatography with Diode Array Detection and Electron Spray Ionization source Mass Spectrometry with Orbitrap analyzer (UPLC-DAD-ESI-MS-Orbitrap). Out of 318 metabolites, we were able to identify 220, of which a majority was amino acids and peptides. Additionally, opine amino acids, amino acid quinones, Amadori compounds, cholines, nucleobases, nucleosides, nucleotides, siderophores, sugars, sugar alcohols and disaccharides were found, as well as other previously reported metabolites from plants or endophytes. Some differences of the metabolic profiles, regarding the amount and identity of the found metabolites, were observed even though the fungi were isolated from the same host. Many of the discovered metabolites have been described possessing biological activities and properties, which may make a favorable contribution to the host plant nutrient availability or abiotic and biotic stress tolerance.

A Bioscreening Technique for Ultraviolet Irradiation Protective Natural Substances

Ultraviolet radiation (UV-R) causes genotoxic and aging effects on skin, and sunscreens are used to alleviate the damage. However, sunscreens contain synthetic shielding agents that can cause harmful effects in the environment. Nature-derived substances may have potential as replacement materials for the harmful sunscreen chemicals. However, screening of a broad range of samples is tedious, and often requires a separate genotoxicity assessment. We describe a simple microplate technique for the screening of UV protective substances using a recombinant Escherichia coli biosensor. Both absorbance-based and bioactivity-based shields can be detected with simultaneous information about the sample genotoxicity. With this technique, a controversial sunscreen compound, oxybenzone offers physical or absorbance-based shield but appears genotoxic at higher concentrations (3.3 mg/mL). We also demonstrate that pine needle extract (Pi_Ne ) shields the biosensor from UV-R in a dose-dependent manner without showing genotoxicity. The physical shield of 5 mg/mL Pi_Ne was similar to that of one of the most common UV-shielding compound TiO₂ concentration 0.80 mg/mL. The bioactivity-based shield of Pi_Ne also reaches the extent of the physical shield with the highest concentration (3.3 mg/mL). We conclude that our technique is suitable in detecting the UV-shielding potential of natural substances, and gives simultaneous information on genotoxicity.

Scots pine aminopropyltransferases shed new light on evolution of the polyamine biosynthesis pathway in seed plants

Background and Aims

Polyamines are small metabolites present in all living cells and play fundamental roles in numerous physiological events in plants. The aminopropyltransferases (APTs), spermidine synthase (SPDS), spermine synthase (SPMS) and thermospermine synthase (ACL5), are essential enzymes in the polyamine biosynthesis pathway. In angiosperms, SPMS has evolved from SPDS via gene duplication, whereas in gymnosperms APTs are mostly unexplored and no SPMS gene has been reported. The present study aimed to investigate the functional properties of the SPDS and ACL5 proteins of Scots pine (Pinus sylvestris L.) in order to elucidate the role and evolution of APTs in higher plants.

Methods

Germinating Scots pine seeds and seedlings were analysed for polyamines by high-performance liquid chromatography (HPLC) and the expression of PsSPDS and PsACL5 genes by in situ hybridization. Recombinant proteins of PsSPDS and PsACL5 were produced and investigated for functional properties. Also gene structures, promoter regions and phylogenetic relationships of PsSPDS and PsACL5 genes were analysed.

Key Results

Scots pine tissues were found to contain spermidine, spermine and thermospermine. PsSPDS enzyme catalysed synthesis of both spermidine and spermine. PsACL5 was found to produce thermospermine, and PsACL5 gene expression was localized in the developing procambium in embryos and tracheary elements in seedlings.

Conclusions

Contrary to previous views, our results demonstrate that SPMS activity is not a novel feature developed solely in the angiosperm lineage of seed plants but also exists as a secondary property in the Scots pine SPDS enzyme. The discovery of bifunctional SPDS from an evolutionarily old conifer reveals the missing link in the evolution of the polyamine biosynthesis pathway. The finding emphasizes the importance of pre-existing secondary functions in the evolution of new enzyme activities via gene duplication. Our results also associate PsACL5 with the development of vascular structures in Scots pine.

Moderate stress responses and specific changes in polyamine metabolism characterize Scots pine somatic embryogenesis

Somatic embryogenesis (SE) is one of the methods with the highest potential for the vegetative propagation of commercially important coniferous species. However, many conifers, including Scots pine (Pinus sylvestris L.), are recalcitrant to SE and a better understanding of the mechanisms behind the SE process is needed. In Scots pine SE cultures, embryo production is commonly induced by the removal of auxin, addition of abscisic acid (ABA) and the desiccation of cell masses by polyethylene glycol (PEG). In the present study, we focus on the possible link between the induction of somatic embryo formation and cellular stress responses such as hydrogen peroxide protection, DNA repair, changes in polyamine (PA) metabolism and autophagy. Cellular PA contents and the expression of the PA metabolism genes arginine decarboxylase (ADC), spermidine synthase (SPDS), thermospermine synthase (ACL5) and diamine oxidase (DAO) were analyzed, as well as the expression of catalase (CAT), DNA repair genes (RAD51, KU80) and autophagy-related genes (ATG5, ATG8) throughout the induction of somatic embryo formation in Scots pine SE cultures. Among the embryo-producing SE lines, the expression of ADC, SPDS, ACL5, DAO, CAT, RAD51, KU80 and ATG8 showed consistent profiles. Furthermore, the overall low expression of the stress-related genes suggests that cells in those SE lines were not stressed but recognized the ABA+PEG treatment as a signal to trigger the embryogenic pathway. In those SE lines that were unable to produce embryos, cells seemed to experience the ABA+PEG treatment mostly as osmotic stress and activated a wide range of stress defense mechanisms. Altogether, our results suggest that the direction to the embryogenic pathway is connected with cellular stress responses in Scots pine SE cultures. Thus, the manipulation of stress response pathways may provide a way to enhance somatic embryo production in recalcitrant Scots pine SE lines.

Expression of catalase and retinoblastoma-related protein genes associates with cell death processes in Scots pine zygotic embryogenesis

BACKGROUND

The cell cycle and cellular oxidative stress responses are tightly controlled for proper growth and development of Scots pine (Pinus sylvestris L.) seed. Programmed cell death (PCD) is an integral part of the embryogenesis during which megagametophyte cells in the embryo surrounding region (ESR) and cells in the nucellar layers face death. In the present study, we show both the tissue and developmental stage specific expression of the genes encoding the autophagy related ATG5, catalase (CAT), and retinoblastoma related protein (RBR) as well as the connection between the gene expressions and cell death programs.

RESULTS

We found strong CAT expression in the cells of the developing embryo throughout the embryogenesis as well as in the cells of the megagametophyte and the nucellar layers at the early embryogeny. The CAT expression was found to overlap with both the ATG5 expression and hydrogen peroxide localization. At the late embryogeny, CAT expression diminished in the dying cells of the nucellar layers as well as in megagametophyte cells, showing the first signs of incipient cell death. Accumulation of starch and minor RBR expression were characteristic of megagametophyte cells in the ESR, whereas strong RBR expression was found in the cells of the nucellar layers at the late embryogeny.

CONCLUSIONS

Our results suggest that ATG5, CAT, and RBR are involved in the Scots pine embryogenesis and cell death processes. CAT seems to protect cells against hydrogen peroxide accumulation and oxidative stress related cell death especially during active metabolism. The opposite expression of RBR in the ESR and nucellar layers alongside morphological characteristics emphasizes the different type of the cell death processes in these tissues. Furthermore, the changes in ATG5 and RBR expressions specifically in the megagametophyte cells dying by necrotic cell death suggest the genetic regulation of developmental necrosis in Scots pine embryogenesis.

Water availability influences morphology, mycorrhizal associations, PSII efficiency and polyamine metabolism at early growth phase of Scots pine seedlings

Scots pine (Pinus sylvestris L.) is adapted to various soil types with diverse water availabilities. However, Scots pine seedlings are vulnerable to abiotic stress during the early growth, when they may be exposed to both dry and wet conditions. Here, we focused on the above and below ground coping strategies of Scots pine seedlings under controlled wet, optimal and dry soil conditions by investigating morphological traits including seedling biomass, number of root tips, proportion of mycorrhizal root tips and brown needles. In addition, we studied metabolic and physiological responses including gene expression involved in biosynthesis and catabolism of polyamines (PA), PSII efficiency and the expression of the catalase (CAT) late-embryogenesis abundant protein (LEA), pyruvate decarboxylase (PDC), glutamate-cysteine ligase (GCL) and glutathione synthetase (GS) genes. We found that seedlings invested in shoots by maintaining stable shoot water content and high PSII efficiency under drought stress. Free and soluble conjugated putrescine (Put) accumulated in needles under drought stress, suggesting the role of Put in protection of photosynthesizing tissues. However, the expression of the PA biosynthesis genes, arginine decarboxylase (ADC), spermidine synthase (SPDS) and thermospermine synthase (ACL5) was not affected under drought stress whereas catabolizing genes diamino oxidase (DAO) and polyamine oxidase (PAO) were down-regulated in shoots. The morphology of the roots was affected by peat water content. Furthermore, both drought stress and water excess restricted the seedling ability to sustain a symbiotic relationship. The consistent pattern of endogenous PAs seems to be advantageous to the Scots pine seedlings also under stress conditions.

Interaction with ectomycorrhizal fungi and endophytic Methylobacterium affects nutrient uptake and growth of pine seedlings in vitro

Tissues of Scots pine (Pinus sylvestris L.) contain several endophytic microorganisms of which Methylobacterium extorquens DSM13060 is a dominant species throughout the year. Similar to other endophytic bacteria, M. extorquens is able to colonize host plant tissues without causing any symptoms of disease. In addition to endophytic bacteria, plants associate simultaneously with a diverse set of microorganisms. Furthermore, plant-colonizing microorganisms interact with each other in a species- or strain-specific manner. Several studies on beneficial microorganisms interacting with plants have been carried out, but few deal with interactions between different symbiotic organisms and specifically, how these interactions affect the growth and development of the host plant. Our aim was to study how the pine endophyte M. extorquens DSM13060 affects pine seedlings and how the co-inoculation with ectomycorrhizal (ECM) fungi [Suillus variegatus (SV) or Pisolithus tinctorius (PT)] alters the response of Scots pine. We determined the growth, polyamine and nutrient contents of inoculated and non-inoculated Scots pine seedlings in vitro. Our results show that M. extorquens is able to improve the growth of seedlings at the same level as the ECM fungi SV and PT do. The effect of co-inoculation using different symbiotic organisms was seen in terms of changes in growth and nutrient uptake. Inoculation using M. extorquens together with ECM fungi improved the growth of the host plant even more than single ECM inoculation. Symbiotic organisms also had a strong effect on the potassium content of the seedling. The results indicate that interaction between endophyte and ECM fungus is species dependent, leading to increased or decreased nutrient content and growth of pine seedlings.

Promoting human health through forests: overview and major challenges

This review aims to contribute to the ongoing discussion about human health, global change, and biodiversity by concentrating on the relationships between forests and human health. This review gives a short overview of the most important health benefits that forests provide to humans, and the risks that forests may pose to human health. Furthermore, it discusses the future challenges for the research on the links between forests and human health, and for delivering health through forests in practice. Forests provide enormous possibilities to improve human health conditions. The results of a vast amount of research show that forest visits promote both physical and mental health by reducing stress. Forests represent rich natural pharmacies by virtue of being enormous sources of plant and microbial material with known or potential medicinal or nutritional value. Forest food offers a safety net for the most vulnerable population groups in developing countries, and healthy forest ecosystems may also help in regulation of infectious diseases. Utilizing forests effectively in health promotion could reduce public health care budgets and create new sources of income. Main challenges to delivering health through forests are due to ecosystem and biodiversity degradation, deforestation, and climate change. In addition, major implementation of research results into practice is still lacking. Inadequate implementation is partly caused by insufficient evidence base and partly due to the lack of policy-makers' and practitioners' awareness of the potential of forests for improving human health. This calls for strong cooperation among researchers, policy-makers, and practitioners as well as between different sectors, especially between health and environmental professionals.

Polyamine metabolism during exponential growth transition in Scots pine embryogenic cell culture

Polyamine (PA) metabolism was studied in liquid cultures of Scots pine (Pinus sylvestris L.) embryogenic cells. The focus of the study was on the metabolic changes at the interphase between the initial lag phase and the exponential growth phase. PA concentrations fluctuated in the liquid cultures as follows. Putrescine (Put) concentrations increased, whereas spermidine (Spd) concentrations decreased in both free and soluble conjugated PA fractions. The concentrations of free and soluble conjugated spermine (Spm) remained low, and small amounts of excreted PAs were also found in the culture medium. The minor production of secondary metabolites reflected the undifferentiated stage of the embryogenic cell culture. Put was produced via the arginine decarboxylase (ADC) pathway. Futhermore, the gene expression data suggested that the accumulation of Put was caused neither by an increase in Put biosynthesis nor by a decrease in Put catabolism, but resulted mainly from the decrease in the biosynthesis of Spd and Spm. Put seemed to play an important role in cell proliferation in Scots pine embryogenic cells, but the low pH of the culture medium could also, at least partially, be the reason for the accumulation of endogenous Put. High Spd concentrations at the initiation of the culture, when cells were exposed to stress and cell death, suggested that Spd may act not only as a protector against stress but also as a growth suppressor, when proliferative growth is not promoted. All in all, Scots pine embryogenic cell culture was proved to be a favourable experimental platform to study PA metabolism and, furthermore, the developed system may also be beneficial in experiments where, e.g., the effect of specific stressors on PA metabolism is addressed.

Ectomycorrhization of Tricholoma matsutake and two major conifers in Finland-an assessment of in vitro mycorrhiza formation

This study aimed to test the ability of Tricholoma matsutake isolates to form mycorrhizas with aseptic seedlings of Pinus sylvestris L. and Picea abies (L.) Karst. Germinated seedlings of Scots pine and Norway spruce were separately inoculated with either isolates originating from Finland or Japan. Eight months after inoculation, the Finnish isolate had formed a sheath and Hartig net on both host species. Ectomycorrhizal Scots pine seedlings inoculated with the Finnish isolate showed the same shoot height and dry mass as the controls. Ectomycorrhizal Norway spruce seedlings inoculated with the Finnish isolate had similar shoot height but slightly less dry mass than the control seedlings. For both tree species, inoculation with the Finnish isolate resulted in reduced total nitrogen content per seedling, but carbon content was unaffected. Inoculation with the Japanese isolate resulted in an initial Hartig net-like structure in pine but not in spruce. No typical Hartig net was observed on either tree species. Furthermore, seedlings of both species inoculated with the Japanese isolate showed significantly reduced growth, dry mass, nitrogen, and carbon content per seedling and shoot height (in spruce) compared to the controls. This study documents and describes the in vitro ectomycorrhization between T. matsutake and Scots pine or Norway spruce and the variable mycorrhizal structures that matsutake isolates can form.

Mycorrhiza formation is not needed for early growth induction and growth-related changes in polyamines in Scots pine seedlings in vitro

Ectomycorrhizal (ECM) fungi have been shown to improve growth of the host plant before the formation of physical ECM structures, i.e. during the so-called pre-mycorrhizal phase. In the present study, changes in growth and the concentrations of individual polyamines (PAs) were followed during the mycorrhiza formation in Scots pine (Pinus sylvestris) seedlings in the presence of two ECM fungi, Pisolithus tinctorius and Paxillus involutus. The two fungus stains were chosen because they differed in infection characteristics as well as in PA and auxin production. The results were compared to our earlier study with two Suillus variegatus strains forming ECMs with Scots pine seedlings in vitro. Paxillus was not able to form ECMs whereas Pisolithus formed ECM association with Scots pine seedlings within two weeks. However, Paxillus enhanced the growth of the seedlings more than Pisolithus. Paxillus also increased putrescine (Put) concentrations of the seedlings in the pre-mycorrhizal phase much more than Pisolithus. A similar trend was observed in the free spermidine (Spd) in stems, whereas in the needles Paxillus decreased free Spd concentration. Pisolithus caused a threefold greater increase in root free Spd than Paxillus. Effects of Paxillus on the growth and PA fluctuation, excluding root free Spd, of the host plant resembled that observed in our previous in vitro study on S. variegatus-Scots pine interaction. Therefore, changes in specific PA concentrations in the pre-mycorrhizal phase seem to be related to growth induction by the ECM fungus rather than to mycorrhiza formation. Moreover, we suggest that growth induction in host plants is not necessarily followed by ECM formation.

Dealing with the problem of non-specific in situ mRNA hybridization signals associated with plant tissues undergoing programmed cell death

BACKGROUND

In situ hybridization is a general molecular method typically used for the localization of mRNA transcripts in plants. The method provides a valuable tool to unravel the connection between gene expression and anatomy, especially in species such as pines which show large genome size and shortage of sequence information.

RESULTS

In the present study, expression of the catalase gene (CAT) related to the scavenging of reactive oxygen species (ROS) and the polyamine metabolism related genes, diamine oxidase (DAO) and arginine decarboxylase (ADC), were localized in developing Scots pine (Pinus sylvestris L.) seeds. In addition to specific signals from target mRNAs, the probes continually hybridized non-specifically in the embryo surrounding region (ESR) of the megagametophyte tissue, in the remnants of the degenerated suspensors as well as in the cells of the nucellar layers, i.e. tissues exposed to cell death processes and extensive nucleic acid fragmentation during Scots pine seed development.

CONCLUSIONS

In plants, cell death is an integral part of both development and defence, and hence it is a common phenomenon in all stages of the life cycle. Our results suggest that extensive nucleic acid fragmentation during cell death processes can be a considerable source of non-specific signals in traditional in situ mRNA hybridization. Thus, the visualization of potential nucleic acid fragmentation simultaneously with the in situ mRNA hybridization assay may be necessary to ensure the correct interpretation of the signals in the case of non-specific hybridization of probes in plant tissues.

Pine embryogenesis: many licences to kill for a new life

In plants, programmed cell death (PCD) is an important mechanism that controls normal growth and development as well as many defence responses. At present, research on PCD in different plant species is actively carried out due to the possibilities offered by modern methods in molecular biology and the increasing amount of genome data. The pine seed provides a favourable model for PCD because it represents an interesting inheritance of seed tissues as well as an anatomically well-described embryogenesis during which several tissues die via morphologically different PCD processes.

One tissue, two fates: different roles of megagametophyte cells during Scots pine embryogenesis

In the Scots pine (Pinus sylvestris L.) seed, embryos grow and develop within the corrosion cavity of the megagametophyte, a maternally derived haploid tissue, which houses the majority of the storage reserves of the seed. In the present study, histochemical methods and quantification of the expression levels of the programmed cell death (PCD) and DNA repair processes related genes (MCA, TAT-D, RAD51, KU80, and LIG) were used to investigate the physiological events occurring in the megagametophyte tissue during embryo development. It was found that the megagametophyte was viable from the early phases of embryo development until the early germination of mature seeds. However, the megagametophyte cells in the narrow embryo surrounding region (ESR) were destroyed by cell death with morphologically necrotic features. Their cell wall, plasma membrane, and nuclear envelope broke down with the release of cell debris and nucleic acids into the corrosion cavity. The occurrence of necrotic-like cell death in gymnosperm embryogenesis provides a favourable model for the study of developmental cell death with necrotic-like morphology and suggests that the mechanism underlying necrotic cell death is evolutionary conserved.

Spermidine and the ectomycorrhizal fungus Pisolithus tinctorius synergistically induce maturation of Scots pine embryogenic cultures

Exogenous spermidine (Spd) and the ectomycorrhizal (ECM) fungus Pisolithus tinctorius (Pers.) Coker and Couch had a synergistic effect on the maturation of Scots pine (Pinus sylvestris L.) somatic embryos. Induced maturation was expressed as a higher number of cell masses able to form embryos and a greater number of embryos formed per cell mass. In contrast, treatment with P. tinctorius alone on the hormone-free medium resulted in the lowest embryo-forming capacity. Retarded proliferation growth appeared to be required for maturation, but did not explain the synergistic effect of the fungus and exogenous Spd. Simultaneous treatment did not result in lower concentrations of putrescine (Put), Spd or spermine (Spm) in the embryogenic cell masses relative to the separate treatments. Our study is the first report on the use of a specific ECM fungus to induce maturation of somatic embryos, and it indicates that P. tinctorius was able to modify the maturation media in a way that, together with exogenous Spd, positively affected embryogenic cultures of Scots pine. Our study also shows that it is possible to enhance plant development other than root formation by using specific ECM fungi.

Suillus variegatus causes significant changes in the content of individual polyamines and flavonoids in Scots pine seedlings during mycorrhiza formation in vitro

Changes in the concentrations of individual flavonoids and polyamines (PAs) in Scots pine (Pinus sylvestris L.) cotyledonary seedlings were studied during the establishment of an ectomycorrhizal (ECM) symbiosis with two Suillus variegatus strains in vitro. Both flavonoids and PAs were analysed after 3, 7, and 14 d in dual culture, and changes in concentrations were compared with growth of the seedlings. Both S. variegatus strains caused similar responses in Scots pine seedlings. Free putrescine accumulated immediately but only transiently after inoculation. This was followed by continuous accumulation of PA conjugates in needles and stems, and free spermidine and spermine in roots, which was accompanied by mycorrhiza formation and improved growth. The fungi induced lateral root formation and main root and primary needle elongation. Inoculation caused no qualitative changes in flavonoid composition, while quantitative changes in flavonols, catechins, and condensed tannins were observed in shoots during mycorrhiza formation. These results indicate that in this in vitro system conjugated PAs and specific flavonoids, generally related to the plant's defence reactions, did not play a major role in the regulation of the establishment of the ectomycorrhizal (ECM) symbiosis in Scots pine roots. The results also clearly show that positive growth responses in shoots and roots due to S. variegatus were supported by different and highly specific changes in the synthesis of both primary and secondary metabolites in these parts of the seedling.

Consistency of polyamine profiles and expression of arginine decarboxylase in mitosis during zygotic embryogenesis of Scots pine

In this study, we show that both arginine decarboxylase (ADC) protein and mRNA transcript are present at different phases of mitosis in Scots pine (Pinus sylvestris) zygotic embryogenesis. We also examined the consistency of polyamine (PA) profiles with the effective temperature sum, the latter indicating the developmental stage of the embryos. PA metabolism was analyzed by fitting statistical regression models to the data of free and soluble conjugated PAs, to the enzyme activities of ADC and ornithine decarboxylase (ODC), as well as to the gene expression of ADC. According to the fitted models, PAs typically had the tendency to increase at the early stages but decrease at the late stages of embryogenesis. Only the free putrescine fraction remained stable during embryo development. The PA biosynthesis strongly preferred the ADC pathway. Both ADC gene expression and ADC enzyme activity were substantially higher than putative ODC gene expression or ODC enzyme activity, respectively. ADC gene expression and enzyme activity increased during embryogenesis, which suggests the involvement of transcriptional regulation in the expression of ADC. Both ADC mRNA and ADC protein localized in dividing cells of embryo meristems and more specifically within the mitotic spindle apparatus and close to the chromosomes, respectively. The results suggest the essential role of ADC in the mitosis of plant cells.

Changes in polyamine content and localization of Pinus sylvestris ADC and Suillus variegatus ODC mRNA transcripts during the formation of mycorrhizal interaction in an in vitro cultivation system

The involvement of polyamines (PAs) in the interaction between Pinus sylvestris L. seedlings and an ectomycorrhizal fungus Suillus variegatus (Swatz: Fr.) O. Kunze was studied in an in vitro cultivation system. PA concentrations in seedlings were analysed after 1, 3, and 5 weeks in dual culture with S. variegatus, and changes in PA pools were compared with the growth of the seedlings. Pinus sylvestris arginine decarboxylase (ADC) and S. variegatus ornithine decarboxylase (ODC) mRNA transcripts were localized during the formation of mycorrhizas. During mycorrhiza formation, Suillus variegatus ODC transcripts were found in developing hyphal mantle and Hartig net, and P. sylvestris ADC transcripts in specific root parenchyma cells adjacent to tracheids and in mitotic cells of the root apical meristem. However, no unambiguous difference in ADC transcript localization between inoculated and non-inoculated roots was observed. Regardless of the unchanged distribution of ADC transcripts, inoculation with S. variegatus increased free putrescine, spermidine, and spermine concentrations in roots within the first week in dual culture. The concentration of free and conjugated putrescine and conjugated spermidine also increased in the needles due to the fungus. The fungus-induced lateral root formation and main root elongation were greatest between the first and third week in dual culture, coinciding with retarded accumulation or a decrease of free PAs. These results show that accumulation of PAs in the host plant is one of the first indicators of the establishment of ectomycorrhizal interaction between P. sylvestris and S. variegatus in the in vitro system.

Polyamine profiles of healthy and parasite-infected Vaccinium myrtillus plants under nitrogen enrichment

Addition of nitrogen (N) to the field layer of boreal forests has been shown to increase the occurrence of the parasitic fungus Valdensia heterodoxa on Vaccinium myrtillus plants. We investigated whether N addition to soil alters the levels of polyamines in V. myrtillus shoots, and discuss here whether such changes could promote the spread of the parasitic fungus on V myrtillus. Using HPLC, we analyzed the concentrations of free and conjugated polyamines in healthy and naturally V. heterodoxa-infected V. myrtillus plants, which had received a moderate or high dose of N fertilizer, or no additional N. Fertilization with N increased the concentrations of free diamines (putrescine and diaminopropane), but had no significant effect on conjugated amines. Thus, N-induced changes in the constitutive levels of soluble conjugated amines do not seem to explain the increased parasite susceptibility of V. myrtillus under N enrichment. Generally, the concentrations of free diamines and insoluble conjugated putrescine were higher in diseased than in healthy shoots, suggesting parasite-induced accumulation of diamines. Free spermine seemed to accumulate in unfertilized, diseased plants, but in fertilized plants this induction was dampened, suggesting that N-induced alterations in spermine metabolism may promote the spread of parasites on V. myrtillus under N-enrichment.

Does extraction of DNA and RNA by magnetic fishing work for diverse plant species?

An automated nucleic acid extraction procedure with magnetic particles originally designed for isolation of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) from animal tissues was tested for plant material. We isolated genomic DNA and total RNA from taxonomically diverse plant species representing conifers (Scots pine), broad-leaved trees (silver birch and hybrid aspen), dwarf shrubs (bilberry), and both monocotyledonous (regal lily) and dicotyledonous (Saint John's wort, round-leaved sundew, and tobacco) herbaceous plants. Buffers developed for DNA extraction were successfully used in addition to manufacturer's extraction kits. The quality of RNA was appropriate for many applications, but the quality of DNA was not always sufficient for polymerase chain reaction (PCR) amplification. However, we could strikingly improve the quality by eliminating the adherent compounds during the extraction or later in the PCR phase. Our results show that the use of the procedure could be extended to diverse plant species. This procedure is especially suitable for small sample sizes and for simultaneous processing of many samples enabling large-scale plant applications in population genetics, or in the screening of putative transgenic plants.

Ectomycorrhizal fungal species and strains differ in their ability to produce free and conjugated polyamines

Production of free and conjugated polyamines by one strain of Laccaria proxima (Boud.) Maire, three strains (H, O, K) of Paxillus involutus (Batsch) Fr., and one strain of Pisolithus tinctorius was studied in vitro. Spermidine (Spd) was the main polyamine in the 4-week-old mycelium of all the fungi. It was mainly present in the free form, but it also occurred in conjugated forms. Paxillus involutus strain H released large amounts of free putrescine (Put), and the Pisolithus tinctorius released a compound probably related to cadaverine (Cad). On the other hand, these two fungi contained less conjugated polyamines than the other fungi. In addition to the amounts, the forms (perchloric acid soluble and insoluble) of conjugated polyamines in the mycelium varied between species and strains. L. proxima contained nearly as much insoluble conjugated Spd as free Spd, whereas Paxillus involutus strains O and K contained relatively large amounts of soluble conjugated Spd. The results suggest that ectomycorrhizal fungal species and strains differ in their ability and need to produce conjugated polyamines. The small amounts of soluble conjugated polyamines found in the culture filtrates indicate that some specific conjugated polyamines may be involved in polyamine translocation across the plasma membrane.

Defoliation-induced responses in peroxidases, phenolics, and polyamines in scots pine (Pinus sylvestris L.) needles

Effects of artificial defoliation on defensive needle chemistry in Scots pine (Pitus sylvestris L.) were evaluated with particular emphasis on peroxidases, phenolic compounds, soluble sugars, polyamines, and foliar nitrogen levels. The study was carried out on a nutrient-poor Scots pine stand with 8- to 25-year-old trees. Defoliation treatment consisted of repeated defoliation in two successive years with respective control trees. Defoliation was done before needle flushing by removing all mature needles. Guaiacol peroxidase activity increased in the needles after the first defoliation. The difference between treatments diminished towards autumn, and disappeared before the second defoliation in the next summer. After the second defoliation, the activities showed a similar trend. Apparently, peroxidases are involved in inducible chemical changes and recovery reactions that occur in the intact needles shortly after defoliation. After the second defoliation, total nitrogen concentration in the current year needles was about 20% lower, and free putrescine (a polyamine) concentration was 40% lower in the defoliated trees than in control needles. These changes indicate a loss of nitrogen due to defoliation. Specific phenolic compounds such as quercitrin, (+)-catechin, and two catechin derivatives increased in current year needles in response to defoliation. Accumulation of starch and sucrose in the current year needles of repeatedly defoliated trees may imply decreased assimilate transport. The results are indicative that changes in needle phytochemistry in response to defoliation accompany changes in needle nitrogen metabolism.

Effects of exogenous diamines on the interaction between ectomycorrhizal fungi and adventitious root formation in Scots pine in vitro

Production of free and conjugated polyamines by two ectomycorrhizal fungi, Pisolithus tinctorius (Pers.) Coker and Couch and Paxillus involutus (Batsch) Fr., was studied in vitro. Spermidine was the main polyamine in the mycelium of both fungi. Paxillus involutus also produced large amounts of the diamine putrescine, whereas Pisolithus tinctorius contained traces of the diamine cadaverine and released into the culture medium an unknown compound probably related to cadaverine or N-methylputrescine. Both fungi accelerated adventitious root formation and increased subsequent root growth of Scots pine (Pinus sylvestris L.) hypocotyl cuttings in vitro. Exogenous cadaverine enhanced rooting caused by Pisolithus tinctorius and also promoted mycorrhiza formation by the fungus. Putrescine and Paxillus involutus had a synergistic effect on root initiation, but not on subsequent root growth. We conclude that specific diamines may be involved in the interaction between ectomycorrhizal fungi and adventitious root formation in Scots pine, and that the effects of specific exogenous polyamines are dependent on the fungal strain and its ability to produce these compounds. The finding that Paxillus involutus enhanced rooting and root growth without mycorrhiza formation indicates that fungal-induced rooting is not necessarily related to visible mycorrhiza formation.

Ozone-induced free polyamine response in scots pine in northern Finland

The study aimed to assess the ozone-induced response in Scots pine (Pinus sylvestris L.) needles by measuring free polyamine concentrations. An open-top chamber experiment with realistically elevated ozone concentrations was carried out in northern Finland. A carry-over effect was detected: the concentrations of free polyamines, especially putrescine, were decreased at the beginning of the next growing season in the ozone-exposed trees. This indicates that the free polyamine pathway was not activated by ozone stress in Scots pines in northern conditions.

Endogenous polyamine content and metabolism in the ectomycorrhizal fungus Paxillus involutus

Endogenous polyamine content of the ectomycorrhizal fungus Paxillus involutus, as well as the activity of its biosynthetic enzymes in relation to mycelia ageing were investigated in this work. Polyamines in free, PCA-soluble and insoluble conjugated forms, are present in Paxillus involutus mycelia in relatively high amounts and the ratio of putrescine to spermidine is age-dependent. Both arginine- and ornithine-decarboxylases are present, but putrescine biosynthesis proceeds mostly via ornithine decarboxylase and decreases with the age of mycelia. There was a large release of free polyamines from mycelia which showed age-dependent features. Clear polyamine uptake was observed in 2-wk-old mycelia and no competition between putrescine and cadaverine was detected. Putrescine uptake seems to reduce ornithine decarboxylase activity, but does not affect arginine decarboxylase.

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.

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).

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.

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.

Nitrate metabolism in Scots pine seedlings during their first growing season

Fluctuations in nitrate reductase activity (NRA), nitrate, nitrite, protein and total nitrogen content of bare-root Scots pine seedlings (Pinus sylvestris L.) raised outdoors were investigated during the first growing season. Nitrate reductase activity was higher in roots than in needles, whereas NO(3) (-) content was higher in needles than in roots and increased in both from June to October. Nitrate reductase activity in roots correlated more closely with NO(3) (-) N in the soil than did NO(3) (-) in the roots. In autumn, there was a closer correlation between foliar NRA and NO(3) (-) in the needles than with NO(3) (-)-N in the soil. Nitrite was not detected in the seedlings during the growing season. Total nitrogen content decreased toward the autumn, whereas protein content initially decreased but increased again in autumn. Acrylic netting placed above the seedlings increased both air and soil temperatures and apparently accelerated the use of nitrate.