Influence of In Vitro Human Digestion Simulation on the Phenolics Contents and Biological Activities of the Aqueous Extracts from Turkish Cistus Species.

Oxidative stress is one of the significant precursors of various metabolic diseases such as diabetes, Parkinson's disease, cardiovascular diseases, cancer, etc. Various scientific reports have indicated that secondary plant metabolites play an important role in preventing oxidative stress and its harmful effects. In this respect, this study was planned to investigate the phenolic profile and antioxidant and antidiabetic potentials of the aqueous extracts from Turkish Cistus species by employing in vitro methods. In vitro digestion simulation procedure was applied to all extracts to estimate the bioavailability of their phenolic contents. Total phenolic, flavonoid, phenolic acid and proanthocyanidin contents were determined for all phases of digestion. In addition, changes in the quantity of the assigned marker flavonoids (tiliroside, hyperoside and quercitrin) were monitored by High-Performance Thin Layer Chromatography (HPTLC) analysis. The antioxidant activity potentials of the extracts were studied by various methods to reveal their detailed activity profiles. On the other hand, in vitro α-amylase and α-glucosidase enzymes and advanced-glycation end product (AGE) inhibitory activities of the extracts were determined to evaluate the antidiabetic potentials of extracts. The results showed that aqueous extracts obtained from the aerial parts of Turkish Cistus species have rich phenolic contents and potential antioxidant and antidiabetic activities; however, their bioactivity profiles and marker flavonoid concentrations might significantly be affected by human digestion. The results exhibited that total phenolic contents, antioxidant activities and diabetes-related enzyme inhibitions of the bioavailable samples were lower than non-digested samples in all extracts.

Linking jasmonates with vitamin E accumulation in plants: a case study in the Mediterranean shrub Cistus albidus L.

MAIN CONCLUSION: Jasmonic acid positively modulates vitamin E accumulation, but the latter can also partly influence the capacity to accumulate the jasmonic acid precursor, 12-oxo-phytodienoic acid, in white-leaved rockrose (Cistus albidus L.) plants growing in their natural habitat. This study suggests a bidirectional link between chloroplastic antioxidants and lipid peroxidation-derived hormones in plants. While vitamin E is well known for its antioxidant properties being involved in plant responses to abiotic stress, jasmonates are generally related to biotic stress responses in plants. Studying them in non-model plants under natural conditions is crucial for the knowledge on their relationship, which will help us to better understand mechanisms and limits of stress tolerance to implement better conservation strategies in vulnerable ecosystems. We studied a typical Mediterranean shrub, white-leaved rockrose (Cistus albidus) under natural conditions during three winters and we analyzed both α and γ-tocopherol, and the three main jasmonates forms 12-oxo-phytodienoic acid (OPDA), jasmonic acid (JA), and jasmonoyl-isoleucine (JA-Ile). We found that JA contents positively correlated with vitamin E accumulation, most particularly with γ-tocopherol, the precursor of α-tocopherol (the most active vitamin E form). This finding was confirmed by exogenous application of methyl jasmonate (MeJA) in leaf discs under controlled conditions, which increased γ-tocopherol when applied at 0.1 mM MeJA and α-tocopherol at 1 mM MeJA. Furthermore, a complementary meta-analysis study with previously published reports revealed a positive correlation between JA and vitamin E, although this relationship turned to be strongly species specific. A strong negative correlation was observed, however, between total tocopherols and OPDA (a JA precursor located in chloroplasts). This antagonistic effect was observed between α-tocopherol and OPDA, but not between γ-tocopherol and OPDA. It is concluded that (i) variations in jasmonates and vitamin E due to yearly, inter-individual and sun orientation-driven variability are compatible with a partial regulation of vitamin E accumulation by jasmonates, (ii) vitamin E may also exert a role in the modulation of the biosynthesis of OPDA, with a much smaller effect, if any, on other jasmonates, and (iii) a trade-off in the accumulation of vitamin E and jasmonates might occur in the regulation of biotic and abiotic stress responses in plants.

Biosynthesis of copper oxide nanoparticles and their potential synergistic effect on alloxan induced oxidative stress conditions during cardiac injury in Sprague-Dawley rats.

Cistus incanus leaf extract was used to biologically synthesize Copper oxide nanoparticles (CuO NPs). The characteristic UV-vis spectral band of CuO NPs found at 290 nm revealed the successful formation of CuO NPs. By the analysis of TEM and SEM, it is confirmed that the obtained CuO NPs were in spherical structure. By the analysis of Fourier transform infrared (FTIR) spectroscopy, it is evident that the absorption peak was situated at a position of about 480 cm-1 of wavenumber, which is typically considered as an extremely pure CuO NPs. The images of Transmission Electron Microscopy exhibited that the formed CuO NPs were in the size of about 15-25 nm and were relatively uniform in distribution. When related with the treatment of nanomaterials only, the synergistic interaction among CuO NPs and oxidative stress conditions considerably decreased the cardiac-related function catalogs, which includes pathological progressions of myocardium along with an obvious rise in the levels of creatine kinase-MB and cardiac troponin I. When compared to the void reaction of micro-CuO and cardiac operations in alloxan-injected rats, aggravation in the conditions of oxidative stress could be playing a significant part in the heart injury after dual exposing CuO NPs and alloxan. By these results, it is confirmed that the conditions of oxidative stress improved the contrary effects of CuO NPs to the heart, signifying that the utilization of nanomaterials in conditions of stress such as, in the delivery of drug, required to be cautiously monitored.

Dissecting Adaptation Mechanisms to Contrasting Solar Irradiance in the Mediterranean Shrub Cistus incanus.

Molecular mechanisms that are the base of the strategies adopted by Mediterranean plants to cope with the challenges imposed by limited or excessive solar radiation during the summer season have received limited attention. In our study, conducted on C. incanus plants growing in the shade or in full sunlight, we performed measurements of relevant physiological traits, such as leaf water potential, gas exchange and PSII photochemistry, RNA-Seq with de-novo assembly, and the analysis of differentially expressed genes. We also identified and quantified photosynthetic pigments, abscisic acid, and flavonoids. Here, we show major mechanisms regulating light perception and signaling which, in turn, sustain the shade avoidance syndrome displayed by the 'sun loving' C. incanus. We offer clear evidence of the detrimental effects of excessive light on both the assembly and the stability of PSII, and the activation of a suite of both repair and effective antioxidant mechanisms in sun-adapted leaves. For instance, our study supports the view of major antioxidant functions of zeaxanthin in sunny plants concomitantly challenged by severe drought stress. Finally, our study confirms the multiple functions served by flavonoids, both flavonols and flavanols, in the adaptive mechanisms of plants to the environmental pressures associated to Mediterranean climate.

A pool-weighted perspective on the two-water-worlds hypothesis.

The 'two-water-worlds' hypothesis is based on stable isotope differences in stream, soil and xylem waters in dual isotope space. It postulates no connectivity between bound and mobile soil waters, and preferential plant water uptake of bound soil water sources. We tested the pool-weighted impact of isotopically distinct water pools for hydrological cycling, the influence of species-specific water use and the degree of ecohydrological separation. We combined stable isotope analysis (δ18 O and δ2 H) of ecosystem water pools of precipitation, groundwater, soil and xylem water of two distinct species (Quercus suber, Cistus ladanifer) with observations of soil water contents and sap flow. Shallow soil water was evaporatively enriched during dry-down periods, but enrichment faded strongly with depth and upon precipitation events. Despite clearly distinct water sources and water-use strategies, both species displayed a highly opportunistic pattern of root water uptake. Here we offer an alternative explanation, showing that the isotopic differences between soil and plant water vs groundwater can be fully explained by spatio-temporal dynamics. Pool weighting the contribution of evaporatively enriched soil water reveals only minor annual impacts of these sources to ecosystem water cycling (c. 11% of bulk soil water and c. 14% of transpired water).

Mediterranean herb extracts inhibit microbial growth of representative oral microorganisms and biofilm formation of Streptococcus mutans.

In light of the growing antibiotic resistance, the usage of plant-derived antimicrobial agents could serve as an effective alternative treatment against oral infections. The aim of this study was to investigate the antimicrobial and antibiofilm activity of Mediterranean herb extracts against representative oral microorganisms. The extraction procedures and the analysis of the obtained extracts were performed under established experimental conditions. The minimum inhibitory (MIC) and bactericidal (MBC) concentrations of the methanol extracts of Cistus creticus ssp. creticus, Cistus monspeliensis, Origanum vulgare, Rosmarinus officinalis, Salvia sclarea and Thymus longicaulis against eight typical oral bacteria and the fungus Candida albicans were determined. The antibiofilm activity against Streptococcus mutans was also quantified using the microtiter plate test. Overall, all tested extracts inhibited effectively the screened obligate anaerobic microorganisms and in concentrations ≥0.3 mg ml-1 had moderate to high antibiofilm activity comparable to that of chlorhexidine (CHX) against S. mutans. In particular, R. officinalis (MIC: 0.08-5.00 mg ml-1) and S. sclarea (MIC: 0.08-2.50 mg ml-1) showed the highest antibacterial activity, while Cistus spp., R. officinalis and S. sclarea significantly inhibited S. mutans biofilm formation at 0.60, 1.25 and 2.50 mg ml-1, respectively. Porphyromonas gingivalis and Parvimonas micra were high susceptible to O. vulgare (MIC = 0.30 mg ml-1), whereas T. longicaulis eradicated all oral bacteria (MBC: 0.15-2.50 mg ml-1). Nevertheless, C. albicans showed no sensitivity to the tested extracts. In conclusion, the tested plant extracts could serve as alternative natural antibacterial and antibiofilm components against oral infections.

Soil Perturbation in Mediterranean Ecosystems Reflected by Differences in Free-Lipid Biomarker Assemblages.

Environmental information provided by free lipids in soil samples collected from control and disturbed plots (Madrid, Spain) was assessed by comparing molecular assemblages of terpenoids and distribution patterns of alkanes and fatty acids (FAs) analyzed by gas chromatography-mass spectrometry (GC-MS). Wildfires in pine forests led to increased proportions of retene, dehydroabietin, and simonellite. Friedo-oleananes were characteristic in soils under angiosperms, and norambreinolide-type diterpenes were characteristic in soils encroached by Cistus bushes. Steroids were major compounds in pastured sites. Enhanced Shannon's lipid biodiversity index in disturbed soils compared with in control soils suggested patterns of recent lipids overlapping a preserved original lipid signature. The extent of the environmental impacts was illustrated as Euclidean distances between paired control and disturbed sites calculated using the compounds in alkyl homologous series as descriptors. As expected, reforestation, bush encroachment, wildfires, and cultivation were reflected by changes in the molecular record of lipids in soils.

Volatile diterpene emission by two Mediterranean Cistaceae shrubs.

Mediterranean vegetation emits a wide range of biogenic volatile organic compounds (BVOCs) among which isoprenoids present quantitatively the most important compound class. Here, we investigated the isoprenoid emission from two Mediterranean Cistaceae shrubs, Halimium halimifolium and Cistus ladanifer, under controlled and natural conditions, respectively. For the first time, diurnal emission patterns of the diterpene kaurene were detected in real-time by Proton-Transfer-Reaction-Time-of-Flight-Mass-Spectrometer. Kaurene emissions were strongly variable among H. halimifolium plants, ranging from 0.01 ± 0.003 to 0.06 ± 0.01 nmol m-2 s-1 in low and high emitting individuals, respectively. They were in the same order of magnitude as monoterpene (0.01 ± 0.01 to 0.11 ± 0.04 nmol m-2 s-1) and sesquiterpene (0.01 ± 0.01 to 0.52 nmol m-2 s-1) emission rates. Comparable range and variability was found for C. ladanifer under natural conditions. Labelling with 13C-pyruvate suggested that emitted kaurene was not derived from de novo biosynthesis. The high kaurene content in leaves, the weak relationship with ecophysiological parameters and the tendency of higher emissions with increasing temperatures in the field indicate an emission from storage pools. This study highlights significant emissions of kaurene from two Mediterranean shrub species, indicating that the release of diterpenes into the atmosphere should probably deserve more attention in the future.

Antibacterial potential of the Cistus incanus L. phenolics as studied with use of thin-layer chromatography combined with direct bioautography and in situ hydrolysis.

The main aim of this study was to detect and identify antibacterial components of fraction I derived from eleven commercial C. incanus herbal teas. Fraction I obtained by a well-established phytochemical protocol of a multi-step extraction was expected to contain flavonoid aglycons alone. Antibacterial profile of fraction I was demonstrated by means of thin-layer chromatography - direct bioautography (TLC-DB) using a Gram positive B. subtilis and a Gram negative A. fischeri strain. Six chromatographic zones of fraction I exhibited a well pronounced antibacterial potential. In qualitative terms, a good agreement was observed among chromatographic fingerprints and the corresponding bioautograms of the eleven samples. The compounds isolated from the six zones were analyzed by HPLC- diode array detector (DAD)-electrospray ionization (ESI)-MS. High numerical m/z values valid for certain constituents of these isolates suggested that some selected antibacterial components are, unexpectedly, flavonoid glycosides. In order to confirm this suggestion, three independent HPTLC methods (multi-development on amino phase and two two-dimensional developments on silica gel phase) were devised to in situ hydrolyze flavonoid glycosides and then separate and visualize the liberated glucose and some other building blocks of the zones' components. Additionally, the sensitivity of glucose detection with p-aminobenzoic acid reagent was enhanced by paraffin. In that way, the presence of the kaempferol glycosides (and not only the aglycones alone) in fraction I was confirmed. Beside kaempferol, p-coumaric acid as a building block unit was shown by HPLC-DAD-MS analysis of the hydrolyzed isolates. Results proved apigenin, kaempferide and acylated kaempferol glycosides (cis- and trans-tiliroside and their conjugates with p-coumaric acid) to be antibacterial components of fraction I. Because isomers of the coumaric acid conjugated tiliroside were detected only in fraction I and not in the crude C. incanus extract, they are regarded as artifacts produced through fractionation.

Provenance effect on carbon assimilation, photochemistry and leaf morphology in Mediterranean Cistus species under chilling stress.

The potential resilience of shrub species to environmental change deserves attention in those areas threatened by climate change, such as the Mediterranean Basin. We asked if leaves produced under different climate conditions through the winter season to spring can highlight the leaf traits involved in determining potential resilience of three Cistus spp. to changing environmental conditions and to what extent intraspecific differences affect such a response. We analysed carbon assimilation, maximum quantum efficiency of PSII photochemistry (Fv /Fm ) and leaf morphological control of the photosynthetic process in leaves formed through the winter season into spring in C. creticus subsp. eriocephalus (CE), C. salvifolius (CS) and C. monspeliensis (CM) grown from seed of different provenances under common garden conditions. Intraspecific differences were found in Fv /Fm for CE and CS. Carbon assimilation-related parameters were not affected by provenance. Moreover, our analysis highlighted that the functional relationships investigated can follow seasonal changes and revealed patterns originating from species-specific differences in LMA arising during the favourable period. Cistus spp. have great ability to modify the structure and function of their leaves in the mid-term in order to cope with changing environmental conditions. The Fv /Fm response to chilling reveals that susceptibility to photoinhibition is a trait under selection in Cistus species. Concerning carbon assimilation, differing ability to control stomatal opening was highlighted between species. Moreover, seasonal changes of the functional relationships investigated can have predictable consequences on species leaf turnover strategies.

Highlighting the differential role of leaf paraheliotropism in two Mediterranean Cistus species under drought stress and well-watered conditions.

The differential degree by which paraheliotropism may counterbalance the deleterious impact of high irradiance between congeneric species in relation to different water availabilities has been poorly investigated. We followed the evolution of gas exchange, quenching analysis and OJIP parameters in restrained (R) and free (F) to move leaves of Cistus monspeliensis (CM) and Cistus salvifolius (CS) under drought stress (WS) and well-watered conditions (WW). Concerning gas exchange parameters, leaf restriction effect was overall not significant in CM except in apparent carboxylation efficiency (Ce) under WS, while CS showed a significant sensitivity of maximum net photosynthetic rate (Amax), stomatal conductance (gs) and Ce even under WW. The recovery analysis highlighted also a faster gs recovery in F leaves. Furthermore, in both the species, restriction affected photon allocation pathways especially in terms of light-regulated and light-independent constitutive non-photochemical energy dissipation under WW, ultimately affecting electron transport rate (ETR). Nevertheless, the OJIP analysis provided us evidences that CM was characterized by a down-regulation of ETR while an impairment occurs in CS. In CM this was due to its ability to modify a certain fraction of reaction centers thus resulting in a higher capability for dissipation of excess light energy under well-watered conditions, not affecting electron transport efficiency. This response was not observed in CS. Overall, we demonstrated that congeneric species, even mostly sharing the same physiological targets, differ in the degree by which leaf movements help to counterbalance the negative effect of the high irradiance in relation with the amount of water available.

Trichome patterning control involves TTG1 interaction with SPL transcription factors.

Epidermal cell differentiation is a paramount and conserved process among plants. In Arabidopsis, a ternary complex formed by MYB, bHLH transcription factors and TTG1 modulates unicellular trichome morphogenesis. The formation of multicellular glandular trichomes of the xerophytic shrub Cistus creticus that accumulate labdane-type diterpenes, has attained much attention renowned for its medicinal properties. Here, we show that C. creticus TTG1 (CcTTG1) interacts with the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPLA/B) proteins, putative homologs of AtSPL4/5 that in turn interact with AtTTG1. These interactions occur between proteins from evolutionarily distant species supporting the conserved function of TTG1-SPL complex. Overexpression of AtSPL4 and AtSPL5 decreased the expression of GLABRA2 (AtGL2), the major regulator of trichome morphogenesis, resulting in trichome reduction on the adaxial surface of cauline leaves, thereby illuminating the significance of TTG1-SPLs interactions in trichome formation control. AtGL2 and AtSPL4 have opposite expression patterns during early stages of leaf development. We postulate an antagonistic effect between SPLs and the heterogeneous MYB-bHLH factors binding to TTG1. Hence, the SPLs potentially rearrange the complex, attenuating its transcriptional activity to control trichome distribution.

Intra-Population Variation of Secondary Metabolites in Cistus ladanifer L.

In previous studies, secondary metabolites in the leaf exudate of Cistus ladanifer, specifically aglycone flavonoids and diterpenes, were demonstrated to play an ecophysiological role. They protect against ultraviolet radiation, have antiherbivore activity, and are allelopathic agents. Their synthesis in the plant was also found to vary quantitatively and qualitatively in response to various environmental factors. In view of these findings, the present work was designed to clarify whether within a single population there are differences among individuals subject to the same environmental conditions. To this end, we analyzed the leaves of 100 individuals of C. ladanifer. The results showed the existence of intrapopulational variation, since, although all the individuals had the same composition of secondary chemistry, the amounts were different. The individuals of a given population of C. ladanifer differ from each other even when growing under similar conditions. According to the ammount of flavonoids and diterpenes observed in each individual, it was possible to distinguish four different groups of individuals. Most individuals, evenly distributed within the population, had low concentrations of the studied compounds, whilst other individuals synthesized greater amounts and were randomly distributed among the former. Given the functions of flavonoids and diterpenes in this species, the quantified intra-population variation may involve greater plasticity for the species in the face of environmental changes.

Antifungal properties of organic extracts of eight Cistus L. species against postharvest citrus sour rot.

UNLABELLED: The effectiveness of methanol and chloroform extracts of eight Cistaceae species to control citrus sour rot decay, caused by Geotrichum citri-aurantii, was investigated in both in vitro and in vivo conditions. Methanol extracts of these plant species exhibited more interesting activity against G. citri-aurantii, in both in vitro and in vivo conditions, compared with chloroforme extracts. Under in vitro trials, obtained results showed that methanol extracts of all tested plants revealed a highest significant antifungal activity with inhibition zones that ranged between 12·33 and 16·33 mm in diameter. All tested methanol extracts totally inhibited spore germination when tested at 10 mg ml(-1) . Incidence of sour rot was significantly lowered to 11·11% when fruits were treated with Cistus populifolius and Cistus ladanifer methanol extracts compared with 100% in the control. The disease severity was lowered to 5·19% and 6·04% when fruits were treated with the same methanol extracts respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: The methanol Cistus extracts had sufficient antifungal activities in vitro and in vivo against G. citri-aurantii to consider its use in the citrus industry after it has been tested under production and natural infection conditions. Such natural products therefore represent a viable alternative approaches for sour rot postharvest management of citrus.

Plant adaptation to extreme environments: the example of Cistus salviifolius of an active geothermal alteration field.

Cistus salviifolius is able to colonise one of the most extreme active geothermal alteration fields in terms of both soil acidity and hot temperatures. The analyses of morpho-functional and physiological characters, investigated in leaves of plants growing around fumaroles (G leaves) and in leaves developed by the same plants after transfer into growth chamber under controlled conditions (C leaves) evidenced the main adaptive traits developed by this pioneer plant in a stressful environment. These traits involved leaf shape and thickness, mesophyll compactness, stomatal and trichome densities, chloroplast size. Changes of functional and physiological traits concerned dry matter content, peroxide and lipid peroxidation, leaf area, relative water and pigment contents. A higher reducing power and antioxidant enzymatic activity were typical of G leaves. Though the high levels of stress parameters, G leaves showed stress-induced specific morphogenic and physiological responses putatively involved in their surviving in active geothermal habitats.

Characterization and role of poly(ADP-ribosyl)ation in the Mediterranean species Cistus incanus L. under different temperature conditions.

In plants, the decline of poly(ADP-ribosyl)ation activity is involved in energy homeostasis and stress tolerance. By reducing stress-induced poly(ADP-ribosyl)ation activity, NAD(+) breakdown is inhibited preventing high energy consumption. Under these conditions, plants preserve their energy homeostasis without an overactivation of mitochondrial respiration, thus avoiding the production of reactive oxygen species. Therefore, plants with lowered poly(ADP-ribosyl)ation activity appear tolerant to multiple stresses. In this study, the evergreen species Cistus incanus L. was used as a model because of its capacity to overcome successfully the environmental constraints of the Mediterranean climate. The aim of the present work was to characterize and assess the role of poly(ADP-ribosyl)ation in C. incanus plants kept under different temperature in greenhouse (GH), outdoor during winter (WO) and outdoor during spring (SO). Data showed that in C. incanus polyADPribose metabolism occurs. The enzyme responsible for poly(ADP-ribose) chains synthesis is a poly(ADP-ribose)polymerase of about 80 kDa, lacking "zinc finger" N-terminal domain and able to automodify. The lowest PARP activity, as well as the lowest quantum yield of PSII linear electron transport (Φ(PSII)) and photochemical quenching (q(P)), was found in WO plants. Instead, in SO plants the recovery of photochemical activity associated to a poly(ADP-ribose)polymerase activity increase of about 50%, as compared to GH plants, was observed. Taking into account both biochemical and eco-physiological responses, a possible explanation for the poly(ADP-ribosyl)ation deficiency in WO plants has been hypothesized.

Plant aging and excess light enhance flavan-3-ol content in Cistus clusii.

Physiological studies on aging in perennials are mainly focused either on the primary metabolism or the hormonal regulation of the process. However, to our knowledge, the involvement of the secondary metabolism in this process has not yet been explored. Cistus clusii, a Mediterranean sclerophyllous evergreen bush, shows considerable amounts of flavan-3-ols in leaves. In the present study, we aimed at determining the impact of environmental conditions and plant aging in the flavan-3-ol content in C. clusii plants grown in field conditions, which included summer drought and recovery periods. Six-year-old plants suffered more from photo-oxidative stress, especially during excess light periods, and showed lower maximum photosynthetic rates than 1-year-old plants. C. clusii leaves accumulated (-)-epigallocatechin gallate in early summer, in a strong positive correlation with both the photon flux density and the photoperiod, but not with the plant water status. Moreover, C. clusii plants accumulated proanthocyanidins (polymeric flavan-3-ols) in leaves during summer. Older plants showed higher levels of proanthocyanidins and (-)-epicatechin, but only during late spring and summer. From the result of the present study, we conclude that excess light enhances flavan-3-ol content in C. clusii, a process enhanced as plants age due to increased excess light stress.

Environmental control of terpene emissions from Cistus monspeliensis L. in natural Mediterranean shrublands.

The large amount of volatile organic compound (VOC) emitted by vegetation modifies air quality contributing to both tropospheric ozone and secondary organic aerosol production. A better understanding of the factors controlling VOC emissions by vegetation is mandatory in order to improve emission estimates derived from tropospheric chemistry models. Although the Mediterranean shrublands are particularly abundant and rich in emitting species, their emission potential is poorly known. Focusing on a VOC-emitting shrub species widespread in the Mediterranean area (Cistus monspeliensis L.), we measured and analysed its emissions of terpenes taking into account the age of individuals, the season of sampling and the soil type. Sampling was done under natural environmental conditions. Species of the genus Cistus are frequently reported to be storing species, although we found only one stored monoterpene and three sesquiterpenes in very low amount. Major emitted compounds were alpha-pinene and beta-myrcene. Total terpene emissions were not influenced by plant age but emission of some individual terpenes was positively correlated with age. A strong seasonal effect was evidenced. A larger amount of terpenes was emitted during spring and summer than during fall and winter. Summer emission rates were nearly 70 times higher than winter emission rates. Total and individual terpene emissions were influenced by soil type; emissions on siliceous substrate were ca. seven times higher than those on calcareous substrate. In conclusion, it appears clearly that environmental factors such as soil nature and season should be taken into account in order to achieve improved modelling of terpene emissions by shrub species.

Transfer of selected mineral nutrients and trace elements in the host-hemiparasite association, Cistus-Odontites lutea, growing on and off metal-polluted sites.

The role of a hemiparasitic life-style in plant resistance to toxic trace elements in polluted soils is unclear. Restriction of metal uptake by the host, restriction of metal transfer from host to parasite, or transformation of metals into a less toxic form may play a role. This study analysed the transfer of selected mineral elements from soil to host (Cistus spp.) and from host to hemiparasite (Odontites lutea) at locations with different metal burdens: a Cu-rich serpentine site, Pb-Ba mine spoil and an unpolluted soil. Highest soil-to-host transfer factors for K, Mg, Ca, Zn, Cu and Pb were observed on the unpolluted soil. Statistically significant differences among locations of host-to-parasite transfer factors were only found for Ca and Pb. Restriction of transfer of unfavourable Ca/Mg ratios, characteristic at the serpentine site, and of high Pb and Zn concentrations at the Pb-Ba mine occurred mainly at the soil-host, and not at the host-parasite, level. Odontites lutea was able to withstand enhanced Zn and Pb concentrations and low Fe/Cu ratios in shoot tissue without developing toxicity symptoms. This could be caused by specific metal resistance mechanisms in this hemiparasite and/or the transformation and transfer of these metals into a less toxic form by the metal-tolerant host.

Meristem aging is not responsible for age-related changes in growth and abscisic acid levels in the Mediterranean shrub, Cistus clusii.

To obtain new insights into the mechanisms underlying aging in perennials, we measured abscisic acid levels, growth and other stress indicators in leaves of Cistus clusii Dunal plants of different ages grown under Mediterranean field conditions. Recently emerged leaves from 9-year-old plants were compared to those of 1-year-old plants (obtained from cuttings from 9-year-old plants) to evaluate the effects of meristem aging on plant aging. Rooting and successful establishment of the cuttings allowed us to compare the physiology of plants with old meristems, but of different size. Plants obtained from cuttings were rejuvenated, with new leaves displaying a higher leaf area and chlorophyll content, but smaller leaf mass per unit area ratios and endogenous abscisic acid levels than those of 9-year-old plants. A comparative study in 1-, 4- and 9-year-old plants revealed that abscisic acid levels increase during the early stages of plant life (with increases of 90% between 1- and 4-year-old plants), but then remain constant at advanced developmental stages (between 4- and 9-year-old plants). Although leaf biomass was 53% smaller in 9-year-old compared to 4-year-old plants, the dry matter produced per shoot apical meristem was equivalent in both plant groups due to an increased number of leaves per shoot in the former. It is concluded that (i) C. clusii plants maintain the capacity to rejuvenate for several years; (ii) newly emerged leaves accumulate higher amounts of abscisic acid during early stages of plant life, but the levels of this phytohormone later remain constant; and (iii) although plant aging leads to the production of smaller leaves, the amount of biomass produced per shoot apical meristem remains constant at advanced developmental stages.