RESUMEN
Norway spruce (Picea abies (L.) Karst) trees are affected by ongoing climate change, including warming and exposure to phytotoxic levels of ozone. Non-volatile terpenoids and volatile terpenoids (biogenic organic volatile compounds, BVOCs) protect spruce against biotic and abiotic stresses. BVOCs also affect the atmosphere's oxidative capacity. Four-year-old Norway spruce were exposed to elevated ozone (EO) (1.4 × ambient) and warming (1.1 °C + ambient air) alone and in combination on an open-field exposure site in Central Finland. Net photosynthesis, needle terpenoid concentrations and BVOC emissions were measured four times during the experiment's second growing season: after bud opening in May, during the mid-growing season in June, and after needle maturation in August and September. Warming increased terpene concentrations in May due to advanced phenology and decreased them at the end of the growing season in matured current-year needles. Ozone enhanced these effects of warming on several compounds. Warming decreased concentrations of oxygenated sesquiterpenes in previous-year needles. Decreased emissions of oxygenated monoterpenes by warming and ozone alone in May were less prominent when ozone and warming were combined. A similar interactive treatment response in isoprene, camphene, tricyclene and α-pinene was observed in August when the temperature and ozone concentration was high. The results suggest long-term warming may reduce the terpenoid-based defence capacity of young spruce, but the defence capacity can be increased during the most sensitive growth phase (after bud break), and when high temperatures or ozone concentrations co-occur. Reduced BVOC emissions from young spruce may decrease the atmosphere's oxidative capacity in the warmer future, but the effect of EO may be marginal because less reactive minor compounds are affected.
Asunto(s)
Ozono , Picea , Ozono/farmacología , Fotosíntesis , Picea/fisiología , Terpenos , Árboles/fisiologíaRESUMEN
To study the effects of slightly elevated temperature and ozone (O3) on leaf structural characteristics of silver birch (Betula pendula Roth), saplings of four clonal genotypes of this species were exposed to elevated temperature (ambient air temperature +0.8-1.0 °C) and elevated O3 (1.3-1.4× ambient O3), alone and in combination, in an open-air exposure field over two growing seasons (2007 and 2008). So far, the impacts of moderate elevation of temperature or the combination of elevated temperature and O3 on leaf structure of silver birch have not been intensively studied, thus showing the urgent need for this type of studies. Elevated temperature significantly increased leaf size, reduced non-glandular trichome density, decreased epidermis thickness and increased plastoglobuli size in birch leaves during one or both growing seasons. During the second growing season, O3 elevation reduced leaf size, increased palisade layer thickness and decreased the number of plastoglobuli in spongy cells. Certain leaf structural changes observed under a single treatment of elevated temperature or O3, such as increase in the amount of chloroplasts or vacuole, were no longer detected at the combined treatment. Leaf structural responses to O3 and rising temperature may also depend on timing of the exposure during the plant and leaf development as indicated by the distinct changes in leaf structure along the experiment. Genotype-dependent cellular responses to the treatments were detected particularly in the palisade cells. Overall, this study showed that even a slight but realistic elevation in ambient temperature can notably modify leaf structure of silver birch saplings. Leaf structure, in turn, influences leaf function, thus potentially affecting acclimation capacity under changing climate.
Asunto(s)
Betula , Ozono/farmacología , Clima , Hojas de la Planta , TemperaturaRESUMEN
Subarctic vegetation is composed of mountain birch [Betula pubescens ssp. czerepanovii (MB)] forests with shrubs and other species growing in the understorey. The effects of the presence and density of one understorey shrub, Rhododendron tomentosum (RT), on the volatile emissions of MB, were investigated in a Finnish subarctic forest site in early and late growing season. Only MB trees with an RT-understorey emitted the RT-specific sesquiterpenoids, palustrol, ledol and aromadendrene. Myrcene, which is the most abundant RT-monoterpene was also emitted in higher quantities by MB trees with an RT-understorey. The effect of RT understorey density on the recovery of RT compounds from MB branches was evident only during the late season when sampling temperature, as well as RT emissions, were higher. MB sesquiterpene and total emission rates decreased from early season to late season, while monoterpene emission rate increased. Both RT and MB terpenoid emission rates were linked to density of foliar glandular trichomes, which deteriorated over the season on MB leaves and emerged with new leaves in the late season in RT. We show that sesquiterpene and monoterpene compounds emitted by understorey vegetation are adsorbed and re-released by MB, strongly affecting the MB volatile emission profile.
Asunto(s)
Betula/química , Monoterpenos/análisis , Rhododendron/química , Compuestos Orgánicos Volátiles/análisis , Finlandia , Hojas de la Planta/química , Sesquiterpenos/análisis , Tricomas/químicaRESUMEN
In radioecology, transfer of radionuclides from soil to plants is typically described by a concentration ratio (CR), which assumes linearity of transfer with soil concentration. Nonlinear uptake is evidenced in many studies, but it is unclear how it should be taken into account in radioecological modeling. In this study, a conventional CR-based linear model, a nonlinear model derived from observed uptake into plants, and a new simple model based on the observation that nonlinear uptake leads to a practically constant concentration in plant tissues are compared. The three models were used to predict transfer of (234)U, (59)Ni and (210)Pb into spruce needles. The predictions of the nonlinear and the new model were essentially similar. In contrast, plant radionuclide concentration was underestimated by the linear model when the total element concentration in soil was relatively low, but within the range commonly observed in nature. It is concluded that the linear modeling could easily be replaced by a new approach that more realistically reflects the true processes involved in the uptake of elements into plants. The new modeling approach does not increase the complexity of modeling in comparison with CR-based linear models, and data needed for model parameters (element concentrations) are widely available.
Asunto(s)
Plomo/metabolismo , Modelos Teóricos , Níquel/metabolismo , Picea/metabolismo , Radioisótopos/metabolismo , Uranio/metabolismo , Hojas de la Planta/metabolismo , Monitoreo de Radiación , Contaminantes Radiactivos del SueloRESUMEN
Different environmental stress factors often occur together but their combined effects on plant secondary metabolism are seldom considered. We studied the effect of enhanced ultraviolet (UV-B) (31% increase) radiation and temperature (ambient +2 °C) singly and in combination on gender-specific emissions of volatile organic compounds (VOCs) from 2-year-old clones of European aspen (Populus tremula L.). Plants grew in 36 experimental plots (6 replicates for Control, UV-A, UV-B, T, UV-A+T and UV-B+T treatments), in an experimental field. VOCs emitted from shoots were sampled from two (1 male and 1 female) randomly selected saplings (total of 72 saplings), per plot on two sampling occasions (June and July) in 2014. There was a significant UV-B×temperature interaction effect on emission rates of different VOCs. Isoprene emission rate was increased due to warming, but warming also modified VOC responses to both UV-A and UV-B radiation. Thus, UV-A increased isoprene emissions without warming, whereas UV-B increased emissions only in combination with warming. Warming-modified UV-A and UV-B responses were also seen in monoterpenes (MTs), sesquiterpenes (SQTs) and green leaf volatiles (GLVs). MTs showed also a UV × gender interaction effect as females had higher emission rates under UV-A and UV-B than males. UV × gender and T × gender interactions caused significant differences in VOC blend as there was more variation (more GLVs and trans-ß-caryophyllene) in VOCs from female saplings compared to male saplings. VOCs from the rhizosphere were also collected from each plot in two exposure seasons, but no significant treatment effects were observed. Our results suggest that simultaneous warming and elevated-UV-radiation increase the emission of VOCs from aspen. Thus the contribution of combined environmental factors on VOC emissions may have a greater impact to the photochemical reactions in the atmosphere compared to the impact of individual factors acting alone.
Asunto(s)
Contaminantes Atmosféricos/metabolismo , Populus/fisiología , Rayos Ultravioleta , Compuestos Orgánicos Volátiles/metabolismo , Atmósfera , Monitoreo del Ambiente , Calentamiento Global , Monoterpenos/metabolismo , Hojas de la Planta/metabolismo , Populus/efectos de la radiación , Estrés Fisiológico , TemperaturaRESUMEN
Uranium (U), cobalt (Co), molybdenum (Mo), nickel (Ni), lead (Pb), thorium (Th) and zinc (Zn) occur naturally in soil but their radioactive isotopes can also be released into the environment during the nuclear fuel cycle. The transfer of these elements was studied in three different trophic levels in experimental mesocosms containing downy birch (Betula pubescens), narrow buckler fern (Dryopteris carthusiana) and Scandinavian small-reed (Calamagrostis purpurea ssp. Phragmitoides) as producers, snails (Arianta arbostorum) as herbivores, and earthworms (Lumbricus terrestris) as decomposers. To determine more precisely whether the element uptake of snails is mainly via their food (birch leaves) or both via soil and food, a separate microcosm experiment was also performed. The element uptake of snails did not generally depend on the presence of soil, indicating that the main uptake route was food, except for U, where soil contact was important for uptake when soil U concentration was high. Transfer of elements from soil to plants was not linear, i.e. it was not correctly described by constant concentration ratios (CR) commonly applied in radioecological modeling. Similar nonlinear transfer was found for the invertebrate animals included in this study: elements other than U were taken up more efficiently when element concentration in soil or food was low.
Asunto(s)
Monitoreo de Radiación , Contaminantes Radiactivos/análisis , Animales , Ecosistema , Plantas , Radioisótopos , Suelo/químicaRESUMEN
Climate warming is having an impact on distribution, acclimation and defence capability of plants. We compared the emission rate and composition of volatile organic compounds (VOCs) from silver birch (Betula pendula (Roth)) provenances along a latitudinal gradient in a common garden experiment over the years 2012 and 2013. Micropropagated silver birch saplings from three provenances were acquired along a gradient of 7° latitude and planted at central (Joensuu 62°N) and northern (Kolari 67°N) sites. We collected VOCs emitted by shoots and assessed levels of herbivore damage of three genotypes of each provenance on three occasions at the central site and four occasions at the northern site. In 2012, trees of all provenances growing at the central site had higher total VOC emission rates than the same provenances growing at the northern site; in 2013 the reverse was true, thus indicating a variable effect of latitude. Trees of the southern provenance had lower VOC emission rates than trees of the central and northern provenances during both sampling years. However, northward or southward translocation itself had no significant effect on the total VOC emission rates, and no clear effect on insect herbivore damage. When VOC blend composition was studied, trees of all provenances usually emitted more green leaf volatiles at the northern site and more sesquiterpenes at the central site. The monoterpene composition of emissions from trees of the central provenance was distinct from that of the other provenances. In summary, provenance translocation did not have a clear effect in the short-term on VOC emissions and herbivory was not usually intense at the lower latitude. Our data did not support the hypothesis that trees growing at lower latitudes would experience more intense herbivory, and therefore allocate resources to chemical defence in the form of inducible VOC emissions.
Asunto(s)
Altitud , Betula/química , Compuestos Orgánicos Volátiles/análisis , Betula/crecimiento & desarrollo , Finlandia , Geografía , Herbivoria , Modelos Lineales , Brotes de la Planta/química , Análisis de Componente Principal , Suelo/química , TemperaturaRESUMEN
The effects of elevated ozone (1.4× ambient) and temperature (ambient +1.3 °C) alone and in combination were studied on the needle cell structure of soil-grown Norway spruce seedlings in the late growing season and winter. Temperature treatment continued over winter and lengthened the snow-free period. Elevated temperature caused microscopic changes related to photosynthesis (decreased chloroplast size and increased number), carbon storage (reduced starch and increased cytoplasmic lipids) and defence (decreased mitochondrial size and proportion per cytoplasm, increased peroxisomes and plastoglobuli, altered appearance of tannins). The results suggest increased oxidative stress by elevated temperature and altered allocation of limited carbon reserve to defence. The number of peroxisomes and plastoglobuli remained high in the outer cells of needles of ozone-exposed seedlings but decreased in the inner cells. This may indicate defence allocation to cells close to the stomata and surface, which are experiencing more oxidative stress. Ozone reduced winter hardiness based on seasonal changes in chloroplast shape and location in the cells. The effects of ozone became evident at the end of the growing season, indicating the effect of cumulative ozone dose or that the seedlings were vulnerable to ozone at the later phases of winter hardening. Elevated temperature increased cellular damage in early winter and visible damage in spring, and the damage was enhanced by ozone. In conclusion, the study suggests that modest air temperature elevation increases stress at the cell structural level in spruce seedlings and is enhanced by low ozone elevation. Future climatic conditions where snow cover is formed later or is lacking but temperatures are low can increase the risk of severe seedling damage, and current and future predicted ozone concentrations increase this risk.
Asunto(s)
Aclimatación , Ozono/farmacología , Picea/fisiología , Pared Celular/metabolismo , Células del Mesófilo/efectos de los fármacos , Células del Mesófilo/fisiología , Células del Mesófilo/ultraestructura , Fotosíntesis/fisiología , Picea/efectos de los fármacos , Picea/ultraestructura , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/fisiología , Hojas de la Planta/ultraestructura , Estaciones del Año , Plantones/efectos de los fármacos , Plantones/fisiología , Plantones/ultraestructura , Temperatura , ÁrbolesRESUMEN
There is a need to incorporate the effects of herbivore damage into future models of plant volatile organic compound (VOC) emissions at leaf or canopy levels. Short-term (a few seconds to 48 h) changes in shoot VOC emissions of silver birch (Betula pendula Roth) in response to feeding by geometrid moths (Erannis defoliaria Hübner) were monitored online by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS). In addition, two separate field experiments were established to study the effects of long-term foliage herbivory (FH, 30-32 days of feeding by geometrids Agriopis aurantiaria (Clerck) and E. defoliaria in two consecutive years) and bark herbivory (BH, 21 days of feeding by the pine weevil (Hylobius abietis L.) in the first year) on shoot and rhizosphere VOC emissions of three silver birch genotypes (gt14, gt15 and Hausjärvi provenance). Online monitoring of VOCs emitted from foliage damaged by geometrid larvae showed rapid bursts of green leaf volatiles (GLVs) immediately after feeding activity, whereas terpenoid emissions had a tendency to gradually increase during the monitoring period. Long-term FH caused transient increases in total monoterpene (MT) emissions from gt14 and sesquiterpene (SQT) emissions from Hausjärvi provenance, mainly in the last experimental season. In the BH experiment, genotype effects were detected, with gt14 trees having significantly higher total MT emissions compared with other genotypes. Only MTs were detected in the rhizosphere samples of both field experiments, but their emission rates were unaffected by genotype or herbivory. The results suggest that silver birch shows a rapid VOC emission response to short-term foliage herbivory, whereas the response to long-term foliage herbivory and bark herbivory is less pronounced and variable at different time points.
Asunto(s)
Betula/fisiología , Herbivoria/fisiología , Compuestos Orgánicos Volátiles/análisis , Betula/genética , Modelos Lineales , Corteza de la Planta/fisiología , Hojas de la Planta/fisiología , Análisis de Componente Principal , Terpenos/análisis , Factores de TiempoRESUMEN
Trees can improve air quality by capturing particles in their foliage. We determined the particle capture efficiencies of coniferous Pinus sylvestris and three broadleaved species: Betula pendula, Betula pubescens and Tilia vulgaris in a wind tunnel using NaCl particles. The importance of leaf surface structure, physiology and moderate soil drought on the particle capture efficiencies of the trees were determined. The results confirm earlier findings of more efficient particle capture by conifers compared to broadleaved plants. The particle capture efficiency of P. sylvestris (0.21%) was significantly higher than those of B. pubescens, T. vulgaris and B. pendula (0.083%, 0.047%, 0.043%, respectively). The small leaf size of P. sylvestris was the major characteristic that increased particle capture. Among the broadleaved species, low leaf wettability, low stomatal density and leaf hairiness increased particle capture. Moderate soil drought tended to increase particle capture efficiency of P. sylvestris.
Asunto(s)
Betula/fisiología , Sequías , Material Particulado/análisis , Pinus sylvestris/fisiología , Hojas de la Planta/fisiología , Adaptación Fisiológica , Contaminantes Atmosféricos/análisis , Betula/ultraestructura , Pinus sylvestris/ultraestructura , Hojas de la Planta/química , Hojas de la Planta/ultraestructuraRESUMEN
In the present experiment, the single and combined effects of elevated temperature and ozone (O(3)) on four silver birch genotypes (gt12, gt14, gt15 and gt25) were studied in an open-air field exposure design. Above- and below-ground biomass accumulation, stem growth and soil respiration were measured in 2008. In addition, a (13)C-labelling experiment was conducted with gt15 trees. After the second exposure season, elevated temperature increased silver birch above- and below-ground growth and soil respiration rates. However, some of these variables showed that the temperature effect was modified by tree genotype and prevailing O(3) level. For instance, in gt14 soil respiration was increased in elevated temperature alone (T) and in elevated O(3) and elevated temperature in combination (O(3) + T) treatments, but in other genotypes O(3) either partly (gt12) or totally nullified (gt25) temperature effects on soil respiration, or acted synergistically with temperature (gt15). Before leaf abscission, all genotypes had the largest leaf biomass in T and O(3) + T treatments, whereas at the end of the season temperature effects on leaf biomass depended on the prevailing O(3) level. Temperature increase thus delayed and O(3) accelerated leaf senescence, and in combination treatment O(3) reduced the temperature effect. Photosynthetic : non-photosynthetic tissue ratios (P : nP ratios) showed that elevated temperature increased foliage biomass relative to woody mass, particularly in gt14 and gt12, whereas O(3) and O(3) + T decreased it most clearly in gt25. O(3)-caused stem growth reductions were clearest in the fastest-growing gt14 and gt25, whereas mycorrhizal root growth and sporocarp production increased under O(3) in all genotypes. A labelling experiment showed that temperature increased tree total biomass and hence (13)C fixation in the foliage and roots and also label return was highest under elevated temperature. Ozone seemed to change tree (13)C allocation, as it decreased foliar (13)C excess amount, simultaneously increasing (13)C excess obtained from the soil. The present results suggest that warming has potential to increase silver birch growth and hence carbon (C) accumulation in tree biomass, but the final magnitude of this C sink strength is partly counteracted by temperature-induced increase in soil respiration rates and simultaneous O(3) stress. Silver birch populations' response to climate change will also largely depend on their genotype composition.
Asunto(s)
Betula/efectos de los fármacos , Cambio Climático , Ozono/farmacología , Temperatura , Árboles/efectos de los fármacos , Betula/genética , Betula/crecimiento & desarrollo , Biomasa , Isótopos de Carbono/metabolismo , Respiración de la Célula , Agricultura Forestal , Genotipo , Micorrizas/efectos de los fármacos , Tallos de la Planta/crecimiento & desarrollo , Microbiología del Suelo , Árboles/genética , Árboles/crecimiento & desarrolloRESUMEN
Cobalt (Co), lead (Pb), molybdenum (Mo), nickel (Ni), uranium (U), and zinc (Zn) are among the elements that have radioactive isotopes in radioactive waste. Soil-to-plant transfer is a key process for possible adverse effects if these radionuclides are accidentally released into the environment. The present study aimed at investigating factors affecting such transfer in boreal forest. The plant species studied were blueberry (Vaccinium myrtillus), May lily (Maianthemum bifolium), narrow buckler fern (Dryopteris carthusiana), rowan (Sorbus aucuparia) and Norway spruce (Picea abies). Regression analyses were carried out to investigate the effects of the chemical composition and physical properties of soil on the soil-to-leaf/needle concentration ratios of Co, Mo, Ni, Pb, U and Zn. Soil potassium (K), magnesium (Mg), manganese (Mn), phosphorus (P) and sulphur (S) concentrations were the most important factors affecting the soil-to-plant transfer of the elements studied. Soil clay and organic matter contents were found to significantly affect plant uptake of Mo, Pb and U. Knowledge of the effects of these factors is helpful for interpretation of the predictions of radioecological models describing soil-to-plant transfer and for improving such models.
Asunto(s)
Magnoliopsida/metabolismo , Metales/metabolismo , Picea/metabolismo , Contaminantes del Suelo/metabolismo , Suelo/química , Metales/química , Hojas de la Planta/metabolismo , Análisis de Componente Principal , Residuos Radiactivos , Contaminantes del Suelo/química , ÁrbolesRESUMEN
Element-specific concentration ratios (CRs) assuming that plant uptake of elements is linear are commonly used in radioecological modelling to describe the soil-to-plant transfer of elements. The goal of this study was to investigate the validity of the linearity assumption in boreal forest plants, for which only limited relevant data are available. The soil-to-plant transfer of three essential (Mo, Ni, Zn) and two non-essential (Pb, U) elements relevant to the safety of radioactive waste disposal was studied. Three understory species (blueberry, narrow buckler fern and May lily) and two tree species (Norway spruce and rowan) were included. Examining CRs as a function of soil concentration showed that CR was not constant but decreased with increasing soil concentrations for all elements and plant species. A non-linear equation fitted fairly well with the empirical data; the R(2)-values for this equation were constantly higher than those for the linear fit. The difference between the two fits was most evident at low soil concentrations where the use of constant CRs underestimated transfer from soil to plants. Site-specific factors affected the transfer of Mo and Ni. The results suggested that systematic variation with soil concentrations explains a part of the large variation of empirically determined CRs, and the accuracy of modelling the soil-to-plant transfer might be improved by using non-linear methods. Non-linearity of soil-to-plant transfer has been previously reported for a few different species, elements and environments. The present study systematically tested the linearity assumption for five elements (both essential and non-essential) and in five boreal forest species representing different growth traits and phylogenies. The data supported non-linearity in all cases.
Asunto(s)
Metales Pesados/metabolismo , Plantas/metabolismo , Monitoreo de Radiación/métodos , Residuos Radiactivos/análisis , Radioisótopos/metabolismo , Contaminantes Radiactivos del Suelo/metabolismo , Ecosistema , Finlandia , Hojas de la Planta/metabolismo , Raíces de Plantas/metabolismo , Reproducibilidad de los Resultados , Suelo/química , Especificidad de la EspecieRESUMEN
In long-term safety assessment models for radioactive waste disposal, uptake of radionuclides by plants is an important process with possible adverse effects in ecosystems. Cobalt-60, (59,63)Ni, (93)Mo, and (210)Pb are examples of long-living radionuclides present in nuclear waste. The soil-to-plant transfer of stable cobalt, nickel, molybdenum and lead and their distribution across plant parts were investigated in blueberry (Vaccinium myrtillus), May lily (Maianthemum bifolium), narrow buckler fern (Dryopteris carthusiana), rowan (Sorbus aucuparia) and Norway spruce (Picea abies) at two boreal forest sites in Eastern Finland. The concentrations of all of the studied elements were higher in roots than in above-ground plant parts showing that different concentration ratios (CR values) are needed for modelling the transfer to roots and stems/leaves. Some significant differences in CR values were found in comparisons of different plant species and of the same species grown at different sites. However, large within-species variation suggests that it is not justified to use different CR values for modelling soil-to-plant transfer of these elements in the different boreal forest plant species.
Asunto(s)
Plantas/metabolismo , Residuos Radiactivos/análisis , Contaminantes Radiactivos del Suelo/metabolismo , Radioisótopos de Cobalto/metabolismo , Radioisótopos de Plomo/metabolismo , Hojas de la Planta/metabolismo , Monitoreo de Radiación , Suelo/química , Árboles/metabolismoRESUMEN
The depletion of stratospheric ozone above the Arctic regions may increase the amount of UV-B radiation to which the northern ecosystems are exposed. In this paper, we examine the hypothesis that supplemental UV-B radiation may affect the growth rate and photosynthesis of boreal peatland plants and could thereby affect the carbon uptake of these ecosystems. In this study, we report the effects of 3-year exposure to elevated UV-B radiation (46% above ambient) on the photosynthetic performance and ultrastructure of a boreal sedge Eriophorum russeolum and a moss Warnstorfia exannulata. The experiment was conducted on a natural fen ecosystem at Sodankylä in northern Finland. The effects of UV-B radiation on the light response of E. russeolum CO(2) assimilation and the maximal photochemical efficiency of photosystem II in a dark-adapted state (F(v)/F(m)) were measured in the field. In addition, the effect of supplemental UV-B radiation on organelles of photosynthetic cells was studied by electron microscopy. The UV-B treatment had no effect on the CO(2) assimilation rate of either species, nor did it affect the structure of the cell organelles. On chlorophyll fluorescence, the UV-B exposure had only a temporary effect during the third exposure year. Our results suggested that in a natural ecosystem, even long-term exposure to reasonably elevated UV-B radiation levels does not affect the photosynthesis of peatland plants.
Asunto(s)
Bryopsida/efectos de la radiación , Cyperaceae/efectos de la radiación , Fotosíntesis/efectos de la radiación , Rayos Ultravioleta , Bryopsida/fisiología , Bryopsida/ultraestructura , Respiración de la Célula/efectos de la radiación , Clorofila/metabolismo , Cyperaceae/fisiología , Cyperaceae/ultraestructura , Crecimiento y Desarrollo/efectos de la radiaciónRESUMEN
Northern forest trees are challenged to adapt to changing climate, including global warming and increasing tropospheric ozone (O(3)) concentrations. Both elevated O(3) and temperature can cause significant changes in volatile organic compound (VOC) emissions as well as in leaf anatomy that can be related to adaptation or increased stress tolerance, or are signs of damage. Impacts of moderately elevated O(3) (1.3x ambient) and temperature (ambient + 1 degrees C), alone and in combination, on VOC emissions and leaf structure of two genotypes (2.2 and 5.2) of European aspen (Populus tremula L.) were studied in an open-field experiment in summer 2007. The impact of O(3) on measured variables was minor, but elevated temperature significantly increased emissions of total monoterpenes and green leaf volatiles. Genotypic differences in the responses to warming treatment were also observed. alpha-Pinene emission, which has been suggested to protect plants from elevated temperature, increased from genotype 5.2 only. Isoprene emission from genotype 2.2 decreased, whereas genotype 5.2 was able to retain high isoprene emission level also under elevated temperature. Elevated temperature also caused formation of thinner leaves, which was related to thinning of epidermis, palisade and spongy layers as well as reduced area of palisade cells. We consider aspen genotype 5.2 to have better potential for adaptation to increasing temperature because of thicker photosynthetic active palisade layer and higher isoprene and alpha-pinene emission levels compared to genotype 2.2. Our results show that even a moderate elevation in temperature is efficient enough to cause notable changes in VOC emissions and leaf structure of these aspen genotypes, possibly indicating the effort of the saplings to adapt to changing climate.
Asunto(s)
Ozono/metabolismo , Populus/metabolismo , Temperatura , Compuestos Orgánicos Volátiles/metabolismo , Aclimatación , Butadienos/metabolismo , Genotipo , Hemiterpenos/metabolismo , Pentanos/metabolismo , Hojas de la Planta/anatomía & histología , Hojas de la Planta/genética , Hojas de la Planta/metabolismo , Populus/anatomía & histología , Populus/genéticaRESUMEN
The authors analyzed a suite of leaf characteristics that might help to explain the difference between ozone-sensitive and ozone-tolerant hybrid aspen (Populus tremula L. x Populus tremuloides Michx.) clones. An open-field experiment comprising ambient ozone and 1.5x ambient ozone concentration (about 35 ppb) and two soil nitrogen regimes (60 and 140 kg N ha(-1) year(-1)) was conducted over two growing seasons on potted plants of eight hybrid aspen clones. Four of the clones had previously been determined to be ozone sensitive based on impaired growth in response to elevated ozone concentration. Photosynthetic rate, chlorophyll fluorescence, and concentrations of chlorophyll, protein and carbohydrates were analyzed three times during the second growing season, and foliar phenolic concentrations were measured at the end of the second growing season. Nitrogen amendment counteracted the effects of ozone, but had no effect on growth-related ozone sensitivity of the clones. Ozone-sensitive clones had higher photosynthetic capacity and higher concentrations of Rubisco and phenolics than ozone-tolerant clones, but the effects of ozone were similar in the sensitive and tolerant groups. Nitrogen addition had no effect on phenolic concentration, but elevated ozone concentration increased the concentrations of chlorogenic acid and (+)-catechin. This study suggests that condensed tannins and catechin, but not salicylates or flavonol glycosides, play a role in the ozone tolerance of hybrid aspen.
Asunto(s)
Adaptación Fisiológica/fisiología , Ozono/metabolismo , Hojas de la Planta/metabolismo , Populus/metabolismo , Adaptación Fisiológica/genética , Biomasa , Metabolismo de los Hidratos de Carbono , Quimera , Clorofila/metabolismo , Nitrógeno/metabolismo , Fotosíntesis/fisiología , Complejo de Proteína del Fotosistema II/fisiología , Populus/genética , Populus/crecimiento & desarrollo , Ribulosa-Bifosfato Carboxilasa/metabolismo , Estrés Fisiológico , ÁrbolesRESUMEN
In this review the main growth responses of Finnish birch (Betula pendula, B. pubescens) and aspen species (Populus tremula and P. tremuloides x P. tremula) are correlated with ozone exposure, indicated as the AOT40 value. Data are derived from 23 different laboratory, open-top chamber, and free-air fumigation experiments. Our results indicate that these tree species are sensitive to increasing ozone concentrations, though high intraspecific variation exists. The roots are the most vulnerable targets in both genera. These growth reductions, determined from trees grown under optimal nutrient and water supply, were generally accompanied by increased visible foliar injuries, carbon allocation toward defensive compounds, reduced carbohydrate contents of leaves, impaired photosynthesis processes, disturbances in stomatal function, and earlier autumn senescence. Because both genera have shown complex ozone defense and response mechanisms, which are modified by variable environmental conditions, a mechanistically based approach is necessary for accurate ozone risk assessment.
Asunto(s)
Betula/efectos de los fármacos , Oxidantes Fotoquímicos/toxicidad , Ozono/toxicidad , Populus/efectos de los fármacos , Betula/genética , Betula/crecimiento & desarrollo , Finlandia , Variación Genética , Hojas de la Planta/crecimiento & desarrollo , Tallos de la Planta/crecimiento & desarrollo , Populus/genética , Populus/crecimiento & desarrolloRESUMEN
This review summarizes the main results from a 3-year open top chamber experiment, with two silver birch (Betula pendula Roth) clones (4 and 80) where impacts of 2x ambient [CO2] (EC) and [O3] (EO) and their combination (EC + EO) were examined. Growth, physiology of the foliage and root systems, crown structure, wood properties, and biological interactions were assessed to understand the effects of a future climate on the biology of silver birch. The clones displayed great differences in their reaction to EC and EO. Growth in clone 80 increased by 40% in EC and this clone also appeared O3-tolerant, showing no growth reduction. In contrast, growth in clone 4 was not enhanced by EC, and EO reduced growth with root growth being most affected. The physiological responses of the clones to EO were smaller than expected. We found no O3 effect on net photosynthesis in either of the clones, and many parameters indicated no change compared with chamber controls, suggesting active detoxification and defense in foliage. In EO, increased rhizospheric respiration over time and accelerated leaf senescence was common in both clones. We assumed that elevated O3 offsets the positive effects of elevated CO2 when plants were exposed to combined EC + EO treatment. In contrast, the responses to EC + EO mostly resembled the ones in EC, at least partly due to stomatal closure, which thus reduced O3 flux to the leaves. However, clear cellular level symptoms of oxidative stress were observed also in EC + EO treatment. Thus, we conclude that EC masked most of the negative O3 effects during long exposure of birch to EC + EO treatment. Biotic interactions were not heavily affected. Only some early season defoliators may suffer from faster maturation of leaves due to EO.