Effects of biochar and compost addition in potting substrates on growth and volatile compounds profile of basil (Ocimum basilicum L.)

BACKGROUND

Despite the optimal characteristics of peat, more environmental-friendly materials are needed in the nursery sector, although these must guarantee specific quantitative and qualitative commercial standards. In the present study, we evaluated the influence of biochar and compost as peat surrogates on yield and essential oil profile of two different varieties of basil (Ocimum basilicum var. Italiano and Ocimum basilicum var. minimum). In two 50-day pot experiments, we checked the performances of biochar from pruning of urban trees and composted kitchen scraps, both mixed in different proportions with commercial peat (first experiment), and under different nitrogen (N) fertilization regimes (second experiment), in terms of plant growth and volatile compounds profile of basil.

RESULTS

Total or high substitution of peat with biochar (100% and 50% v.v.) or compost (100%) resulted in seedling death a few days from transplantation, probably because the pH and electrical conductivity of the growing media were too high. Substrates with lower substitution rates (10-20%) were underperforming in terms of plant growth and color compared to pure commercial peat during the first experiment, whereas better performances were obtained by the nitrogen-fertilized mixed substrates in the second experiment, at least for one variety. We identified a total of 12 and 16 aroma compounds of basil (mainly terpenes) in the two experiments. Partial replacement of peat did not affect basil volatile organic compounds content and composition, whereas N fertilization overall decreased the concentration of these compounds.

CONCLUSION

Our results support a moderate use of charred or composted materials as peat surrogates. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Essential Oils for the Conservation of Paper Items

Archival documents and artworks stored in libraries frequently undergo degradative processes promoted by the so-called "biodeteriogens" that inhabit these places. A renewed interest in plant-derived products has arisen in those research groups focusing on cultural heritage preservation and looking for new and safe disinfection techniques. In this view, essential oils (EOs) and their volatile organic constituents are very appealing thanks to their versatility of action. A literature survey of the scientific publications involving EOs and/or their major constituents related to the conservation of paper items of cultural heritage interest is presented here, aiming to reveal benefits and limitations of such peculiar plant-derived compounds.

Essential oils to contrast biodeterioration of the external marble of Florence Cathedral

The search for more sustainable strategies to contrast biodeterioration of stone cultural heritage has been developing in recent years to find alternatives to synthetic biocides, since their toxicity and potential impact on the environment and health. In this study, the application of the oregano and thyme essential oils (EOs) was tested to control microbial growth on the external marble of Florence Cathedral affected by extended darkening. Before in situ application, preliminary tests were carried out to evaluate the interference of the EOs with marble (colorimetric and water absorption assays on marble specimens) and their efficacy in inhibiting marble microbiota (sensitivity test on nutrient media). EOs inhibited the whole cultivable microbiota sampled from the Cathedral marble at a very low concentration, while they did not interfere with colour and water absorption capability of uncolonised marble samples when applied as a 2 % solution. Then the two EOs and the commercial biocide Biotin T were used in in situ trials on marble in two outdoor study sites of Florence Cathedral. The effectiveness of the treatments was assessed through short- and mid-term evaluation by multidisciplinary in situ non-invasive (colorimetric and ATP assays, microscopy) and ex situ (microbial viable titer) tests. Concerning results, we found a good correspondence between parameters for evaluation of viability (bacterial and fungi viable titer) and activity (ATP determination) and some correspondence among these and microscopy and colorimetry. Considering the whole data, treatments with oregano and thyme EOs were effective against microbial community, in more cases comparably to the commercial biocide. Some differences found, particularly by viable titer, in the two study sites or in bacterial and fungal components of the microbiota can be partly attributed to differences in structure and colonization pattern of the microbial community due to the peculiar climatic conditions of the differently exposed study areas.

In vitro and in vivo copper-treated Myrtus communis L.: terpene profiles and evidence for potential cultivation on metal-contaminated soils

The intensive application of agro-chemicals, and in particular of copper (Cu)-based compounds, causes increasing pollution of agricultural land, with serious risks for human health. Aromatic plants used for purposes other than food, can be considered for the exploitation and/or remediation of metal-polluted substrates, since contamination of the essential oils by these metals was not significant. Myrtle (Myrtus communis L.) is a Mediterranean evergreen shrub whose essential oil has many commercial applications. In this work, the effect of an excess of Cu in respect to control conditions was assessed on M. communis growth and foliar terpene composition. Metal accumulation in roots and shoots was also evaluated for the possible use of this species in phytoremediation. The amount of Cu applied in our experiments minimally affected the terpene profiles of in vitro grown plants, whereas no variations were detected in in vivo plants. The presence of the metal in the soil did not significantly impair plant growth, thus allowing its cultivation on polluted substrates. On the other hand, the amount of Cu in the plant was not enough to result in a significant reduction of Cu levels in the soil. Therefore, myrtle plants proved to be good candidates for the re-vegetation of Cu-contaminated lands.

Genomic and metabolic profiling of two tomato contrasting cultivars for tolerance to Tuta absoluta

Dissimilar patterns of variants affecting genes involved in response to herbivory, including those leading to difference in VOC production, were identified in tomato lines with contrasting response to Tuta absoluta. Tuta absoluta is one of the most destructive insect pest affecting tomato production, causing important yield losses both in open field and greenhouse. The selection of tolerant varieties to T. absoluta is one of the sustainable approaches to control this invasive leafminer. In this study, the genomic diversity of two tomato varieties, one tolerant and the other susceptible to T. absoluta infestation was explored, allowing us to identify chromosome regions with highly dissimilar pattern. Genes affected by potential functional variants were involved in several processes, including response to herbivory and secondary metabolism. A metabolic analysis for volatile organic compounds (VOCs) was also performed, highlighting a difference in several classes of chemicals in the two genotypes. Taken together, these findings can aid tomato breeding programs aiming to develop tolerant plants to T. absoluta.

Terpene Profiles Composition and Micromorphological Analysis on Two Wild Populations of Helichrysum spp. from the Tuscan Archipelago (Central Italy)

Two wild populations of Helichrysum (Mill.) located at Elba Island (Tuscan Archipelago, Central Italy) were morphologically and phytochemically analyzed to taxonomically identify H. litoreum (population A) and H. italicum subsp. italicum (population B). Micromorphological and histochemical analyses were performed on the indumentum using Scanning Electron Microscope (SEM) and Light Microscope (LM). Morphometric analyses on vegetative and reproductive traits were also conducted. Finally, a chemotaxonomic analysis was carried out on the terpene profile of flowers, leaves and bark tissues using gas chromatography (GC-MS). Results suggested that morphological discriminant traits were mainly in leaves and cypselae glandular tissues. Phytochemical analysis indicated that a high relative content of α-pinene and β-caryophyllene were the main markers for population A, while a high relative content of neryl-acetate, α-curcumene, isoitalicene and italicene, especially in the terpene profile of bark tissue, were the main compounds for discriminating population B. The analysis suggested that the wild population A could be mainly ascribed to H. litoreum, whilst population B is defined by H. italicum.

Plant Sampling for Production of Essential Oil and Evaluation of Its Antimicrobial Activity In Vitro

Essential oils (EOs) and oleoresins are complex mixtures mainly made up of terpenes, synthesized by a wide variety of plants. Individual terpenes may show broad-spectrum activity against different plant pathogens, and their combination into EO and oleoresin mixtures enhances plant chemical defense. The interest in EOs has significantly increased due to the trend of using natural products as herbicides, insecticidal and antimicrobial agents. In addition, the use of plant mixtures is an emerging approach to face the problem of antimicrobial resistance in agriculture. This chapter reports guidelines about plant sample collection for the production of EOs and provides protocols to test their activity as antimicrobial agents against bacteria and fungi. It also describes a solvent-free method for the inclusion of EOs into β-cyclodextrins. This type of formulate is prepared to turn liquid EOs into easily manageable water-soluble powders, and to control the release of volatile compounds, aiming to increase EOs' applications in agriculture.

Within-Plant Variation in Rosmarinus officinalis L. Terpenes and Phenols and Their Antimicrobial Activity against the Rosemary Phytopathogens Alternaria alternata and Pseudomonas viridiflava

This study investigated within-plant variability of the main bioactive compounds in rosemary (Rosmarinus officinalis L.). Volatile terpenes, including the enantiomeric distribution of monoterpenes, and phenols were analyzed in young and mature foliar, cortical and xylem tissues. In addition, antimicrobial activity of rosmarinic acid and selected terpenes was evaluated against two rosemary pathogens, Alternaria alternata and Pseudomonas viridiflava. Data showed that total concentration and relative contents of terpenes changed in relation to tissue source and age. Their highest total concentration was observed in the young leaves, followed by mature leaves, cortical and xylem tissues. Rosmarinic acid and carnosic acid contents did not show significant differences between leaf tissues of different ages, while young and mature samples showed variations in the content of four flavonoids. These results are useful for a more targeted harvesting of rosemary plants, in order to produce high-quality essential oils and phenolic extracts. Microbial tests showed that several terpenes and rosmarinic acid significantly inhibited the growth of typical rosemary pathogens. Overall, results on antimicrobial activity suggest the potential application of these natural compounds as biochemical markers in breeding programs aimed to select new chemotypes less susceptible to pathogen attacks, and as eco-friendly chemical alternatives to synthetic pesticides.

Isoprene Emission in Darkness by a Facultative Heterotrophic Green Alga

Isoprene is a highly reactive biogenic volatile hydrocarbon that strongly influences atmospheric oxidation chemistry and secondary organic aerosol budget. Many phytoplanktons emit isoprene like terrestrial pants. Planktonic isoprene emission is stimulated by light and heat and is seemingly dependent on photosynthesis, as in higher plants. However, prominent isoprene-emitting phytoplanktons are known to survive also as mixotrophs and heterotrophs. Chlorella vulgaris strain G-120, a unicellular green alga capable of both photoautotrophic and heterotrophic growth, was examined for isoprene emission using GC-MS and real-time PTR-MS in light (+CO₂) and in darkness (+glucose). Chlorella emitted isoprene at the same rate both as a photoautotroph under light, and as an exclusive heterotroph while feeding on exogenous glucose in complete darkness. By implication, isoprene synthesis in eukaryotic phytoplankton can be fully supported by glycolytic pathways in absence of photosynthesis, which is not the case in higher plants. Isoprene emission by chlorophyll-depleted mixotrophs and heterotrophs in darkness serves unknown functions and may contribute to anomalies in oceanic isoprene estimates.

Diversification of petal monoterpene profiles during floral development and senescence in wild roses: relationships among geraniol content, petal colour, and floral lifespan

Wild roses store and emit a large array of fragrant monoterpenes from their petals. Maximisation of fragrance coincides with floral maturation in many angiosperms, which enhances pollination efficiency, reduces floral predation, and improves plant fitness. We hypothesized that petal monoterpenes serve additional lifelong functions such as limiting metabolic damage from reactive oxygen species (ROS), and altering isoprenoid hormonal abundance to increase floral lifespan. Petal monoterpenes were quantified at three floral life-stages (unopened bud, open mature, and senescent) in 57 rose species and 16 subspecies originating from Asia, America, and Europe, and relationships among monoterpene richness, petal colour, ROS, hormones, and floral lifespan were analysed within a phylogenetic context. Three distinct types of petal monoterpene profiles, revealing significant developmental and functional differences, were identified: Type A, species where monoterpene abundance peaked in open mature flowers depleting thereafter; Type B, where monoterpenes peaked in senescing flowers increasing from bud stage, and a rare Type C (8 species) where monoterpenes depleted from bud stage to senescence. Cyclic monoterpenes peaked during early floral development, whereas acyclic monoterpenes (dominated by geraniol and its derivatives, often 100-fold more abundant than other monoterpenes) peaked during floral maturation in Type A and B roses. Early-diverging roses were geraniol-poor (often Type C) and white-petalled. Lifetime changes in hydrogen peroxide (H₂O₂) revealed a significant negative regression with the levels of petal geraniol at all floral life-stages. Geraniol-poor Type C roses also showed higher cytokinins (in buds) and abscisic acid (in mature petals), and significantly shorter floral lifespan compared with geraniol-rich Type A and B roses. We conclude that geraniol enrichment, intensification of petal colour, and lower potential for H₂O₂-related oxidative damage characterise and likely contribute to longer floral lifespan in monoterpene-rich wild roses.

Effects of Soil Fertilization on Terpenoids and Other Carbon-Based Secondary Metabolites in Rosmarinus officinalis Plants: A Comparative Study

Rosmarinus officinalis is an evergreen aromatic plant with important commercial interest as it contains numerous essential oils (composed of terpenoid compounds) and phenolic constituents (natural antioxidant compounds). This work aims at evaluating the concomitant effects of different inorganic and organic fertilization treatments and the subsequent increases in soil nutrient availability on terpenoids and other carbon-based secondary metabolites, e.g., flavonoids and phenolic compounds, in Rosmarinus officinalis leaves. The results showed that, as expected, the structural carbohydrate content (lignocellulosic compounds) in stems was higher in fertilized plants than in controls. Additionally, positive correlations were observed of the absolute amounts of total terpenoids and some single terpenoid compounds with N or P contents in leaves. On the contrary, the phenolic and flavonoid concentrations in all the rosemary plant parts were lower with the fertilization treatments. Indeed, negative correlations between the phenolic compounds (and flavonoids) and N in rosemary leaves were also found. Overall, the results suggest that the terpenoid production's response to fertilization was due to N, which is essential for protein synthesis and terpene synthase activity, and to P, which is necessary for the synthesis of both terpenoid precursors and ATP and NADPH, also needed for terpenoid synthesis. On the other hand, the basis for the fertilization's effects on the production of phenolic compounds is the direct nitrogen trade-off between growth and the shikimic acid pathway by which phenolics compounds are synthesized.

Drought stress modulates secondary metabolites in Brassica oleracea L. convar. acephala (DC) Alef, var. sabellica L

BACKGROUND

Consumer preference today is for the consumption of functional food and the reduction of chemical preservatives. Moreover, the antimicrobial properties and health-promoting qualities of plant secondary metabolites are well known. Due to forecasted climate changes and increasing human population, agricultural practices for saving water have become a concern. In the present study, the physiological responses of curly kale Brassica oleracea L. convar. Acephala (DC) var. sabellica to drought stress and the impact of water limitation on the concentration of selected secondary metabolites were investigated under laboratory-controlled conditions.

RESULTS

Results indicated that drought stress increased the content of trans-2-hexenal, phytol and δ-tocopherol, and decreased chlorophyll content. Moreover, drought stress increased antioxidant capacity and the expression of AOP2, a gene associated with the biosynthesis of aliphatic alkenyl glucosinolates, and of three genes - TGG1, TGGE and PEN2 - encoding for myrosinases, the enzymes involved in glucosinolate breakdown.

CONCLUSION

The present study shows that water limitation during the growing phase might be exploited as a sustainable practice for producing curly kale with a high concentration of nutritionally important health-promoting bioactive metabolites. © 2019 Society of Chemical Industry.

Leaves of isoprene-emitting tobacco plants maintain PSII stability at high temperatures

At high temperatures, isoprene-emitting plants display a higher photosynthetic rate and a lower nonphotochemical quenching (NPQ) compared with nonemitting plants. The mechanism of this phenomenon, which may be very important under current climate warming, is still elusive. NPQ was dissected into its components, and chlorophyll fluorescence lifetime imaging microscopy (FLIM) was used to analyse the dynamics of excited chlorophyll relaxation in isoprene-emitting and nonemitting plants. Thylakoid membrane stiffness was also measured using atomic force microscope (AFM) to identify a possible mode of action of isoprene in improving photochemical efficiency and photosynthetic stability. We show that, when compared with nonemitters, isoprene-emitting tobacco plants exposed at high temperatures display a reduced increase of the NPQ energy-dependent component (qE) and stable (1) chlorophyll fluorescence lifetime; (2) amplitude of the fluorescence decay components; and (3) thylakoid membrane stiffness. Our study shows for the first time that isoprene maintains PSII stability at high temperatures by preventing the modifications of the surrounding environment, namely providing a more steady and homogeneous distribution of the light-absorbing centres and a stable thylakoid membrane stiffness. Isoprene photoprotects leaves with a mechanism alternative to NPQ, enabling plants to maintain a high photosynthetic rate at rising temperatures.

Comparative transcriptional and metabolic responses of Pinus pinea to a native and a non-native Heterobasidion species

Heterobasidion irregulare is a causal agent of root and butt-rot disease in conifers, and is native to North America. In 1944 it was introduced in central Italy in a Pinus pinea stand, where it shares the same niche with the native species Heterobasidion annosum. The introduction of a non-native pathogen may have significant negative effects on a naïve host tree and the ecosystem in which it resides, requiring a better understanding of the system. We compared the spatio-temporal phenotypic, transcriptional and metabolic host responses to inoculation with the two Heterobasidion species in a large experiment with P. pinea seedlings. Differences in length of lesions at the inoculation site (IS), expression of host genes involved in lignin pathway and in cell rescue and defence, and analysis of terpenes at both IS and 12 cm above the IS (distal site, DS), were assessed at 3, 14 and 35 days post inoculation (dpi). Results clearly showed that both species elicit similar physiological and biochemical responses in P. pinea seedlings. The analysis of host transcripts and total terpenes showed differences between inoculation sites and between pathogen and mock inoculated plants. Both pathogen and mock inoculations induced antimicrobial peptide and phenylalanine ammonia-lyase overexpression at IS beginning at 3 dpi; while at DS all the analysed genes, except for peroxidase, were overexpressed at 14 dpi. A significantly higher accumulation of terpenoids was observed at 14 dpi at IS, and at 35 dpi at DS. The terpene blend at IS showed significant variation among treatments and sampling times, while no significant differences were ever observed in DS tissues. Based on our results, H. irregulare does not seem to have competitive advantages over the native species H. annosum in terms of pathogenicity towards P. pinea trees; this may explain why the non-native species has not widely spread over the 73 years since its putative year of introduction into central Italy.

Impact of two arbuscular mycorrhizal fungi on Arundo donax L. response to salt stress

AM symbiosis did not strongly affect Arundo donax performances under salt stress, although differences in the plants inoculated with two different fungi were recorded. The mechanisms at the basis of the improved tolerance to abiotic stresses by arbuscular mycorrhizal (AM) fungi have been investigated mainly focusing on food crops. In this work, the potential impact of AM symbiosis on the performance of a bioenergy crop, Arundo donax, under saline conditions was considered. Specifically, we tried to understand whether AM symbiosis helps this fast-growing plant, often widespread in marginal soils, withstand salt. A combined approach, involving eco-physiological, morphometric and biochemical measurements, was used and the effects of two different AM fungal species (Funneliformis mosseae and Rhizophagus irregularis) were compared. Results indicate that potted A. donax plants do not suffer permanent damage induced by salt stress, but photosynthesis and growth are considerably reduced. Since A. donax is a high-yield biomass crop, reduction of biomass might be a serious agronomical problem in saline conditions. At least under the presently experienced growth conditions, and plant-AM combinations, the negative effect of salt on plant performance was not rescued by AM fungal colonization. However, some changes in plant metabolisms were observed following AM-inoculation, including a significant increase in proline accumulation and a trend toward higher isoprene emission and higher H₂O₂, especially in plants colonized by R. irregularis. This suggests that AM fungal symbiosis influences plant metabolism, and plant-AM fungus combination is an important factor for improving plant performance and productivity, in presence or absence of stress conditions.

Moderate Drought Stress Induces Increased Foliar Dimethylsulphoniopropionate (DMSP) Concentration and Isoprene Emission in Two Contrasting Ecotypes of Arundo donax

The function of dimethylsulphoniopropionate (DMSP) in plants is unclear. It has been proposed as an antioxidant, osmolyte and overflow for excess energy under stress conditions. The formation of DMSP is part of the methionine (MET) pathway that is involved in plant stress responses. We used a new analytical approach to accurately quantify the changes in DMSP concentration that occurred in two ecotypes of the biomass crop Arundo donax subject to moderate drought stress under field conditions. The ecotypes of A. donax were from a hot semi-arid habitat in Morocco and a warm-humid environment in Central Italy. The Moroccan ecotype showed more pronounced reductions in photosynthesis, stomatal conductance and photochemical electron transport than the Italian ecotype. An increase in isoprene emission occurred in both ecotypes alongside enhanced foliar concentrations of DMSP, indicative of a protective function of these two metabolites in the amelioration of the deleterious effects of excess energy and oxidative stress. This is consistent with the modification of carbon within the methyl-erythritol and MET pathways responsible for increased synthesis of isoprene and DMSP under moderate drought. The results of this study indicate that DMSP is an important adaptive component of the stress response regulated via the MET pathway in A. donax. DMSP is likely a multifunctional molecule playing a number of roles in the response of A. donax to reduced water availability.

Terpene arms race in the Seiridium cardinale - Cupressus sempervirens pathosystem

The canker-causing fungus Seiridium cardinale is the major threat to Cupressus sempervirens worldwide. We investigated the production of terpenes by canker-resistant and susceptible cypresses inoculated with S. cardinale, the effect of these terpenes on fungal growth, and the defensive biotransformation of the terpenes conducted by the fungus. All infected trees produced de novo terpenes and strongly induced terpenic responses, but the responses were stronger in the canker-resistant than the susceptible trees. In vitro tests for the inhibition of fungal growth indicated that the terpene concentrations of resistant trees were more inhibitory than those of susceptible trees. The highly induced and de novo terpenes exhibited substantial inhibition (more than a fungicide reference) and had a high concentration-dependent inhibition, whereas the most abundant terpenes had a low concentration-dependent inhibition. S. cardinale biotransformed three terpenes and was capable of detoxifying them even outside the fungal mycelium, in its immediate surrounding environment. Our results thus indicated that terpenes were key defences efficiently used by C. sempervirens, but also that S. cardinale is ready for the battle.

Early physiological responses of Pinus pinea L. seedlings infected by Heterobasidion sp.pl. in an ozone-enriched atmospheric environment

The presence of the American root-rot disease fungus Heterobasidion irregulare Garbel. & Otrosina was detected in Italian coastal pine forests (Pinus pinea L.) in addition to the common native species Heterobasidion annosum (Fries) Brefeld. High levels of tropospheric ozone (O3) as an atmospheric pollutant are usually experienced in Mediterranean pine forests. To explore the effect of interaction between the two Heterobasidion species and ozone pollution on P. pinea, an open-top chamber (OTC) experiment was carried out. Five-year-old P. pinea seedlings were inoculated with the fungal species considered (H. irregulare, H. annosum and mock-inoculation as control), and then exposed in charcoal-filtered open-top chambers (CF-OTC) and non-filtered ozone-enriched chambers (NF+) from July to the first week of August 2010 at the experimental facilities of Curno (North Italy). Fungal inoculation effects in an ozone-enriched environment were assessed as: (i) the length of the inoculation lesion; (ii) chlorophyll a fluorescence (ChlF) responses; and (iii) analysis of resin terpenes. Results showed no differences on lesion length between fungal and ozone treatments, whereas the short-term effects of the two stress factors on ChlF indicate an increased photosynthetic efficiency, thus suggesting the triggering of compensation/repair processes. The total amount of resin terpenes is enhanced by fungal infection of both species, but depressed by ozone to the levels observed in mock-inoculated plants. Variations in terpene profiles were also induced by stem base inoculations and ozone treatment. Ozone might negatively affect terpene defences making plants more susceptible to pathogens and insects.

An innovative approach to the recovery of phenolic compounds and volatile terpenes from the same fresh foliar sample of Rosmarinus officinalis L

Rosmarinus officinalis L. is a plant of relevant commercial interest because of its volatile fraction and also its phenolic constituents which are both well known for their numerous properties. Nevertheless, an extractive method suitable to recovering both the aromatic and phenolic fractions from the same fresh foliar tissue has not yet been reported. In this work we have optimized a two-step procedure able to recover first the phenolic compounds and successively the volatile terpenes from the same foliar sample. The recovery of the whole phenolic fraction, partially degraded using a traditional extractive method, was guaranteed and we observed a significant increment in the amount of volatile terpenes compared to a traditional extraction procedure. We also highlight crucial information on the enzymatic activity of the endogenous oxidases that rapidly transform the phenolic substrates, mainly the rosmarinic acid. Our results suggest that this extractive procedure could also be used for other aromatic plants, thus providing a useful tool for more complete analyses of the main phytochemicals available in fresh foliar samples and creating the possibility of incrementing yields of volatile compounds.

Nutritional and pathogenic fungi associated with the pine engraver beetle trigger comparable defenses in Scots pine

Conifer bark beetles are often associated with fungal complexes whose components have different ecological roles. Some associated species are nutritionally obligate fungi, serving as nourishment to the larvae, whereas others are pathogenic blue-stain fungi known to be involved in the interaction with host defenses. In this study we characterized the local and systemic defense responses of Scots pine (Pinus sylvestris L.) against Ophiostoma brunneo-ciliatum Math. (a blue-stain pathogen) and Hyalorhinocladiella macrospora (Franke-Grosm.) Harr. (a nutritional fungus). These fungi are the principal associates of the pine engraver beetle, Ips acuminatus (Gyll.). Host responses were studied following inoculation with the fungi, singly and as a fungal complex, and by identifying and quantifying terpenoids, phenolic compounds and lignin. Although the length of the necrotic lesions differed between control (wound) and fungal treatments, only two compounds (pinosylvin monomethyl ether and (+)-α-pinene) were significantly affected by the presence of the fungi, indicating that Scots pine has a generic, rather than specific, induced response. The fact that both nutritional and blue-stain fungi triggered comparable induced defense responses suggests that even a non-pathogenic fungus may participate in exhausting host plant defenses, indirectly assisting in the beetle establishment process. Our findings contribute to the further development of current theory on the role of associated fungal complexes in bark beetle ecology.

The impact of winter flooding with saline water on foliar carbon uptake and the volatile fraction of leaves and fruits of lemon (Citrus × limon) trees

We investigated the consequences of recurrent winter flooding with saline water on a lemon (Citrus×limon (L.) Burm.f.) orchard, focussing on photosynthesis limitations and emission of secondary metabolites (isoprenoids) from leaves and fruits. Measurements were carried out immediately after flooding (December), at the end of winter (April) and after a dry summer in which plants were irrigated with optimal quality water (September). Photosynthesis was negatively affected by flooding. The effect was still visible at the end of winter, whereas the photosynthetic rate was fully recovered after summer, indicating an unexpected resilience capacity of flooded plants. Photosynthesis inhibition by flooding was not due to diffusive limitations to CO2 entry into the leaf, as indicated by measurements of stomatal conductance and intercellular CO2 concentration. Biochemical and photochemical limitations seemed to play a more important role in limiting the photosynthesis of flooded plants. In young leaves, characterised by high rates of mitochondrial respiration, respiratory rates were enhanced by flooding. Flooding transiently caused large and rapid emission of several volatile isoprenoids. Emission of limonene, the most abundant compound, was stimulated in the leaves, and in young and mature fruits. Flooding changed the blend of emitted isoprenoids, but only few changes were observed in the stored isoprenoids pool.

Storage method, drying processes and extraction procedures strongly affect the phenolic fraction of rosemary leaves: an HPLC/DAD/MS study

The Rosmarinus officinalis L. is widely known for its numerous applications in the food field but also for the increasing interest in its pharmaceutical properties. Two groups of compounds are mainly responsible for the biological activities of the plant: the volatile fraction and the phenolic constituents. The latter group is mainly constituted by rosmarinic acid, by a flavonoidic fraction and by some diterpenoid compounds structurally derived from the carnosic acid. The aim of our work was to optimize the extractive and analytical procedure for the determination of all the phenolic constituents. Moreover the chemical stability of the main phenols, depending on the storage condition, the different drying procedures and the extraction solvent, have been evaluated. This method allowed to detect up to 29 different constituents at the same time in a relatively short time. The described procedure has the advantage to being able to detect and quantify several classes of compounds, among them numerous minor flavonoids, thus contributing to improving knowledge of the plant. The findings from this study have demonstrated that storing the raw fresh material in the freezer is not appropriate for rosemary, mainly due to the rapid disappearing of the rosmarinic acid during the freezing/thawing process. Regarding the flavonoidic fraction, consistent decrements, were highlighted in the dried samples at room temperature if compared with the fresh leaf. Rosmarinic acid, appeared very sensitive also to mild drying processes. The total diterpenoidic content undergoes to little changes when the leaves are freeze dried or frozen and limited losses are observed working on dried leaves at room temperature. Nevertheless it can be taken in account that this fraction is very sensitive to the water presence during the extraction that favors the conversion of carnosic acid toward it oxidized form carnosol. From our findings, it appear evident that when evaluating the phenolic content in rosemary leaves, several factors, mainly the type of storage, the drying process and the extraction methods, should be carefully taken into account because they can induce partial losses of the antioxidant components.

Systemic effects of Heterobasidion annosum s.s. infection on severity of Diplodia pinea tip blight and terpenoid metabolism in Italian stone pine (Pinus pinea)

Three-year-old seedlings of Pinus pinea L. were inoculated near the stem base with one of two Heterobasidion annosum (Fr.) Bref. sensu stricto (s.s.) strains belonging to two populations: the North American P-group (NAm-P) and the European P-group (Eur-P). The NAm-P strain caused smaller H. annosum stem lesions than the Eur-P strain. Three weeks after the stem inoculations with H. annosum, apical shoots were inoculated with Diplodia pinea (Desmaz.) J. Kick. Basal stem infection with H. annosum resulted in D. pinea causing longer necrotic lesions in the shoots, indicating systemic induced susceptibility (SIS) to this shoot blight pathogen. Furthermore, stem induction with the NAm-P strain resulted in higher susceptibility to D. pinea than stem induction with the Eur-P strain. Total terpene accumulation was suppressed by about 50% in the shoots under attack by D. pinea when seedlings were induced with H. annosum. Total terpene concentration in shoots inoculated with D. pinea was negatively correlated with lesion size, both overall and by stem treatment. Stem base inoculation with H. annosum induced whole-plant changes in terpenoid profiles, but these were not associated with the SIS phenotype. We discuss our findings on modulation of systemic response of P. pinea to fungal attack in the context of tripartite ecological interactions.

Physical and chemical responses of Sitka spruce (Picea sitchensis) clones to colonization by Heterobasidion annosum as potential markers for relative host susceptibility

Forty-one 2-year-old clones of Picea sitchensis (Bong.) Carr. from three full-sib families (14 clones from each of two families and 13 clones from a third family) were either wounded and inoculated with an isolate of Heterobasidion annosum (Fr.) Bref. or wounded without inoculation. Lesion lengths on the inner bark from the point of inoculation varied among clones 35 days after treatment. There was no relationship between lesion length and relatedness within families. Two clones (21342 and 25202) with the shortest lesions, tentatively designated as less susceptible to H. annosum, and two clones (21176 and 27166) with the longest lesions, designated more susceptible, were selected for comparison of host anatomical and chemical responses to infection. The position and structure of the ligno-suberized boundary zone (LSZ) in the bark of the clones suggested that the less susceptible clones formed thicker layers of suberized cells in the LSZ following wounding plus inoculation. No LSZ was observed in two ramets of the more susceptible Clone 27166 following wounding and inoculation with H. annosum. Compared with more susceptible genotypes, clones of P. sitchensis with low susceptibility to H. annosum had high relative proportions of (+)-alpha-pinene, (-)-beta-pinene and one unidentified terpene constituent (Unknown-15) in cortical resin sampled 25 cm from the lesions. In contrast, more susceptible clones had higher relative proportions of (-)-limonene, Unknown-16, Unknown-18 and Unknown-19. In the secondary resin produced in bark tissues surrounding the lesions, proportions of several monoterpene constituents varied; these changes included a decrease in the relative amount of beta-phellandrene and corresponding small increases in some minor constituents. The concentrations of the monoterpenes, except a few minor constituents, increased in the infected tissues. Wounding plus inoculation with H. annosum resulted in varied monoterpene responses, with distinct differences between less susceptible and more susceptible clones. In less susceptible clones, Unknown-19 increased following wounding plus inoculation, whereas in more susceptible clones, concentrations of delta-3-carene and Unknown-13 and Unknown-16 increased. Differences in both constitutive and induced resin monoterpene profiles may provide useful markers for resistance to H. annosum in selection and breeding programs.

Flavonoids and biflavonoids in Tuscan berries of Juniperus communis L.: detection and quantitation by HPLC/DAD/ESI/MS

The aim of the present work was to develop a quali-quantitative investigation, using HPLC/DAD and HPLC/ESI/MS techniques, of the phenolic composition of berries collected from wild Tuscan plants of Juniperus communis L. and grown in three different geographical zones. The applied chromatographic elution method made it possible to well separate up to 16 different compounds belonging to flavonoids, such as isoscutellarein and 8-hydroxyluteolin or hypolaetin glycosides, and six biflavonoids, among them amentoflavone, hynokiflavone, cupressoflavone, and methyl-biflavones. To the best of the authors' knowledge this is the first report on the presence of these compounds in juniper berries. The flavonoidic content in the analyzed berries ranged between 1.46 and 3.79 mg/g of fresh pulp, whereas the amount of the biflavonoids was always lower, varying between 0.14 and 1.38 mg/g of fresh weight.

Characterisation of different clones of Picea abies (L.) Karst using head-space sampling of cortical tissues combined with enantioselective capillary gas chromatography for the separation of chiral and non-chiral monoterpenes

Head-space sampling (HS) has been combined with enantioselective gas chromatography (GC) for the analysis of chiral and non-chiral monoterpenes present in the cortical tissues of five different Norway spruce clones. (1S)-(-)-alpha-Pinene, (1S,5S)-(-)sabinene, (1S)-(-)-beta-pinene, and (4S)-(-)limonene dominated over (1R)-(+)-alpha-pinene, (1R,5R)-(+)-sabinene, (1R)-(+)-beta-pinene, and (4R)-(+)-limonene. Results showed a large variation in the enantiomeric composition of cortical tissues between different clones. The development of HS-GC greatly increased the speed of precise analyses of chiral monoterpenes in small samples and therefore offer excellent opportunities in studies on the ecophysiological and chemotaxomic roles of these chiral components.

Geographical variation in water relations, hydraulic architecture and terpene composition of Aleppo pine seedlings from Italian provinces

Ecotypic variations in leaf conductance, soil-to-leaf hydraulic conductance, components of tissue water potential, hydraulic architecture parameters and xylem embolism were examined in greenhouse-grown two-year-old Aleppo pine (Pinus halepensis Mill.) seedlings from six origins representing the geographic range of the species in Italy. Cortical resin composition of the seedlings was also determined. Measurements were made on well-watered seedlings and on seedlings subjected to recurring severe drought. Drought-stressed seedlings had lower mean leaf conductances, transpiration rates and soil-to-leaf hydraulic conductances than well-watered seedlings. They also exhibited more negative osmotic potentials, higher relative water deficit at incipient plasmolysis, but a similar maximum modulus of elasticity. Drought-stressed seedlings showed a higher degree of xylem embolism, a lower Huber value, lower leaf specific conductivity and lower specific conductivity than well-watered seedlings. Drought-stressed seedlings of provenances from more xeric habitats (Tremiti, Porto Pino and Mottola) had greater leaf conductances, transpiration rates and soil-to-leaf hydraulic conductances than drought-stressed seedlings of provenances from more mesic habitats (Imperia, Otricoli and Vico del Gargano). They also showed higher osmotic adjustment and a lower degree of xylem embolism. Among provenances, there were no significant differences in hydraulic architecture parameters in response to the drought treatment; however, Tremiti and Porto Pino seedlings displayed smaller drought-induced reductions in specific conductivity and leaf specific conductivity, respectively, than seedlings from other provenances. These differences suggest that seedlings from xeric provenances, especially Tremiti, have greater resistance to desiccation than seedlings from mesic provenances. No clear association was found between terpene variability and the other traits investigated, although terpene composition was related to the geographical distribution of the provenances. We conclude that the drought-tolerance responses of Tremiti make it a more suitable provenance than the others for establishment on sites prone to severe soil water deficits.

Response to light of shade-grown beech seedlings subjected to different watering regimes

The morphological and physiological responses (net photosynthesis, stomatal conductance, leaf chlorophyll concentration and leaf orientation) of shade-grown beech seedlings after transfer to a high-light regime were studied in well-watered plants and in plants subjected to water stress. Immediately after exposure to high irradiance, shade-grown seedlings displayed a lower photosynthetic rate, a higher leaf chlorophyll concentration and a more horizontal leaf orientation than light-acclimated plants (control plants). The chlorophyll concentration of shade-grown plants gradually declined throughout the period of exposure to high irradiance reaching the amount observed in control plants. Rates of photosynthesis of shade-grown plants began to recover after 8 days of exposure to high irradiance and recovery was nearly complete after 30 days. Leaf orientation of shade-grown plants also changed rapidly during the first 8 days of exposure to high irradiance and by the end of the experiment, there were no significant differences between shade-grown and control plants. Water stress caused significant declines in net photosynthesis and leaf conductance in both shade-grown and control plants. Net photosynthesis did not recover completely in the shade-grown water-stressed plants during the 30-day exposure to high irradiance. Reversible leaf paraheliotropism and chlorophyll bleaching were observed in response to soil drying followed by rewatering.