1,721,033 research outputs found
The effects of tropospheric ozone on oaks: A global meta-analysis
No full textTropospheric ozone (O3) levels are still elevated in many regions of the world including Northern Hemisphere forests areas, and are predicted to increase further due to anthropogenic activities and climate change. Oaks are major woody angiosperms in the Northern Hemisphere in terms of biodiversity, ecological dominance, and economic values. This meta-analysis shows overwhelming evidence of the O3 effects on 51 growth, anatomical, biomass, physiological and biochemical parameters of 14 deciduous or evergreen oak species distributed all around the Northern Hemisphere. Although no large impacts were observed on biomass, suggesting an O3 tolerance by oaks, some impairments were found at physiological level that might negatively affect carbon sequestration and water vapour transfer to the atmosphere. This outcome suggests the need to incorporate this phenomenon into future projection studies dealingwith how atmospheric change and forest biomeswill interact in effecting climatic change. Among the antioxidants used by oaks to respond to O3, phenols seem to have a crucial role. Deciduous species resultedmore affected by O3 than evergreen ones, aswell as oaks native to Eurasia, in
comparison with those from North-America. Experiments performed in less controlled environments showed more O3 deleterious effects, especially under higher AOT40 levels, but negative impacts were also reported for acute O3 exposures. Most of the reviewed studies with additional treatments to O3 exposure investigated the interaction(s) between O3 and drought, but the negative effects induced by drought seemed not to be exacerbated
by the pollutant. However,more combined experiments on the impact of O3 and co-occurring stressors on woody species are necessary. Another major issue is the lack of experiments on adult trees. To better understand O3 impacts, and to reinforce the strength of O3 impact predictions, O3 controlled experiments on young individuals should be combined with long-term experiments on mature trees grown in open-air conditions
Climate change, ozone and plant life
No full textOzone (O3) is a secondary gaseous pollutant since it is formed, under solar radiation and high temperature, by reactions among precursors, primarily nitrogen oxides and volatile organic compounds (VOCs). Concentrations of ground-level O3 have been increasing over the last century and, despite significant control efforts and legislation to reduce O3 precursor emissions, ground-level O3 is still a major air quality issue over large regions worldwide. The
current tropospheric O3 levels (35-50 ppb in the northern hemisphere) are high enough to damage both forests and crops by reducing growth rates and productivity. Plants are essential players in the context of air pollution scenarios due to O3. They are primary target of O3 toxicity, but – at the same time – they remove pollutants from the atmosphere (mainly during their physiological gas exchange activity), so doing protecting human health. However, many species themselves emit biogenic VOCs, which enter the troposphere to take part to the whirlwind of reactions which bring to photochemical smog and O3 formation. The real impact of O3 on plants is however related to their capacity to respond by detoxification and repair mechanisms.
The production of O3 is controlled by temperature, sunlight and humidity, and by the longrange transport of precursors all of which are sensitive to changes in climate. Many of the processes creating or destroying O3 or delivering it to ground level are influenced by synoptic and local weather patterns. Climate change is thus inherently coupled to changes in regional and local meteorology, which may affect the potential for build-up of plant (and human) harmful levels of O3 in regionally polluted areas.
Globally, an increase in the frequency of high O3 concentrations due to changes in weather and rainfall patterns is expected due to climate change. During the 21st century over Europe, for example, an increased frequency of summer droughts, heat-wave events and associated high O3 episodes is anticipated. Stomatal closure in vegetation under these expected dry conditions will also reduce the absorption of pollutants, one of the dominant processes controlling ground-level O3. On the other hand, increases in O3 will also have indirect effects on global warming, by reducing plant growth and consequently its role in carbon sink for carbon dioxide (CO2), so representing a driver for an increase in the rate of CO2 rise in the atmosphere. Ozone is also an important greenhouse gas, already ranked third behind CO2 and
methane, with a direct radiative forcing on climate of 0.35-0.37 W m-2.
Feed-back reactions are a never ending story when complex processes are involved. A full comprehension of the prediction of the overall continual impact of O3 on plant life under changing climate – able of quantifying effects on ecological processes and provisioning services, but also considering the implications for ecosystem services, and based on a mechanistic and biologically-relevant understanding of the single processes involved across time and space – is so far missing. The road is still long and winding
Leaf demography and growth analysis to assess the impact of air pollution on plants: A case study on alfalfa exposed to a gradient of sulphur dioxide concentrations
Full text linkAlthough air pollution usually leads to a reduction in the overall growth and development of plants, its effects on leaf demography have not been well examined so far. The present study was designed to highlight the capability of the demographic approach, together with traditional growth and other leaf trait analyses, to assess the impact of air pollution on vegetation by exposing plants of Medicago sativa L. (alfalfa) to a long-term gradient of sulphur
dioxide (SO2) concentrations (0, 30, 60 and 90 ppb, for 45 consecutive days). This study shows that (i) alfalfa plants tolerated only the lower SO2 concentration, while detrimental effects on leaf demography and growth were imposed by higher SO2 levels, with a less efficient strategy in carbon gain and allocation found in plants under 60 ppb; (ii) leaf demography and traditional growth analysis leaded to agreeing outcomes, but the demographic
approach detected the stress induced by SO2 sooner; and more generally (iii) demography can be a powerful and non-destructive tool for monitoring plant responses to air pollution, especially considering that the feasibility of this approach will likely increase with the reduction of its operational time related to the rapid expansion of several automated phenotyping techniques
Spectroscopic detection of forest diseases: a review (1970–2020)
Full text linkSustainable forest management is essential to confront the detrimental impacts of diseases on forest ecosystems. This review highlights the potential of vegetation spectroscopy in improving the feasibility of assessing forest disturbances induced by diseases in a timely and cost-effective manner. The basic concepts of vegetation spectroscopy and its application in phytopathology are first outlined then the literature on the topic is discussed. Using several optical sensors from leaf to landscape-level, a number of forest diseases characterized by variable pathogenic processes have been detected, identified and quantified in many country sites worldwide. Overall, these reviewed studies have pointed out the green and red regions of the visible spectrum,
the red-edge and the early near-infrared as the spectral regions most sensitive to the disease development as they are mostly related to chlorophyll changes and symptom development. Late disease conditions particularly affect the shortwave-infrared region, mostly related to water content. This review also highlights some major issues to be addressed such as the need to explore other major forest diseases and geographic areas, to further develop hyperspectral sensors for early detection and discrimination of forest disturbances, to improve devices for remote sensing, to implement longterm
monitoring, and to advance algorithms for exploitation of spectral data. Achieving of these goals will enhance the capability of vegetation spectroscopy in early detection of forest stress and in managing forest diseases
Hyperspectral assessment of plant responses to multi-stress environments: Prospects for managing protected agrosystems
Full text linkAdvancements in our ability to rapidly detect plant responses to stress are necessary to improve crop management practices and meet the global challenge of food security. Using optical approaches to detect plant stress before symptoms become apparent has great potential, but these approaches lack testing in multiple-stress environments and fail to fully exploit the data collected. Using hyperspectral data from lettuce, we show that optical measurements can provide growers with important stress-related information to inform crop management practices. We suggest that
integrating this technology into protected agrosystems, such as greenhouses, could greatly improve crop quality and yield.
• Tools to detect and predict stress pre-visually are essential to optimally manage agrosystems. Here, we investigated the capability of reflectance spectroscopy to characterize responses of asymptomatic crop leaves under multi-stress conditions.
• Full range (350–2,500 nm) reflectance measurements and traditional plant stress responses were collected on lettuce leaves under the combination of different supplemental light types and intensities, fertilization and salinity. Partial leastsquares discriminate analysis and regression modeling and spectral indices were employed to characterize plant responses to multiple stress conditions, both alone and in combination.
• Spectral profiles (400–800 nm + 1,900–2,200 nm) of individuals grown under variable environments were statistically different (p < .05) for multiple combinations. Partial least-squares discriminate analysis accurately classified the different single stressors well (accuracy: 0.76–0.91), but generated moderate accuracies (0.63–0.65) for two-stress combinations, and low accuracy (0.33) for higher order stress combinations. Osmotic potential, and chlorophyll and phenol concentrations were well predicted by spectral data (validation R2: 0.70–0.84). Higher lettuce yield and quality was found under sodium light at high intensity (850 μmol m−2 s−1 photosynthetic active radiation), with high fertilization (150 ppm N) and no salinity.
• Our findings highlight the utility and limitations of vegetation spectroscopy in a protected agrosystem. We suggest that integration of vegetation spectroscopy into intelligent and automated greenhouses and other protected systems could enhance management efficiency, as well as crop quality and yield
Climate change, ozone and plant life
No full textTropospheric ozone (O3) is a global air pollution issue and a pivotal greenhouse gas. Even if the emissions of O3-precursors are reduced, it is expected that there will be an increase in the frequency of high polluted days globally due to the changes in weather (e.g., high temperature, reduced precipitation) expected under future climate change (CC), especially in hot-spot areas such as the Mediterranean basin. Although it is now certain that understanding of the role of O3 pollution on natural and urban ecosystems is crucial to any effort to mitigate CC by stabilizing atmospheric carbon dioxide concentrations, a full comprehension of the prediction of the overall continual impact of O3 under different realistic environmental scenarios is so far missing. The phytopathology group at the Department of Agriculture, Food and Environment of the University of Pisa has a long-running interest in the issue of plant/O3 interactions, and its activities are aimed to cover the gaps and uncertainties on the complex network among CC, O3 pollution and vegetation
Genome Resources of Verticillium dahliae VdGL16: the causal agent of vascular wilt on the invasive species Ailanthus altissima
No full textVerticillium species are known as plant pathogens responsible for wilt diseases in a large variety of dicotyledon plants and crops in many parts of the world. Here we present the draft genome sequence of Verticillium dahliae Kleb. (strain VdGL16) isolated in Italy from the invasive alien species Ailanthus altissima (Mill.; commonly known as tree-of-heaven) showing Verticillium wilt symptoms. The comparison between the newly sequenced genome with those publicly available revealed candidate genes putatively involved in pathogenicity. The genome represents a new useful source for future research on Verticillium genetics and biology as well as research on novel approaches in the control of A. altissima
Spectral phenotyping of physiological and anatomical leaf traits related with maize water status
Full text linkAdvancements in phenotyping techniques capable of rapidly and nondestructively detecting impacts of drought on crops are necessary to meet the 21st-century challenge of food security. Here, we describe the use of hyperspectral reflectance to predict variation in physiological and anatomical leaf traits related with water status under varying water availability in six maize (Zea mays) hybrids that differ in yield stability under drought. We also assessed relationships among traits and collections of traits with yield stability. Measurements were collected in both greenhouse and field environments, with plants exposed to different levels of water stress or to natural water availability, respectively. Leaf spectral measurements were paired with a number of physiological and anatomical reference measurements, and predictive spectral models were constructed using a partial leastsquares regression approach. All traits were relatively well predicted by spectroscopic models, with external validation (i.e. by applying partial least-squares regression coefficients on a dataset distinct from the one used for calibration) goodness-of-fit (R2) ranging from 0.37 to 0.89 and normalized error ranging from 12% to 21%. Correlations between reference and predicted data were statistically similar for both greenhouse and field data. Our findings highlight the capability of vegetation spectroscopy to rapidly and nondestructively identify a number of foliar functional traits affected by drought that can be used as indicators of plant water status. Although we did not detect trait coordination with yield stability in the hybrids used in this study, expanding the range of functional traits estimated by hyperspectral data can help improve trait-based breeding approaches
Defense mechanisms in Salvia officinalis under chronic ozone exposure
No full textTropospheric ozone (O3) is a major air pollutant causing negative effects on health of living organisms. As O3 commonly has adverse effects on plant tissue at both physiological and biochemical levels, the present study investigated the mechanisms of response of sage, Salvia officinalis – an aromatic herb largely grown in the Mediterranean area – to a chronic O3 exposure (120 ppb of O3 for 36 consecutive days, 5 h day-1), specifically focusing on the relationships between the oxidative burst and the regulation of phytohormones and their interaction as an integrated defense mechanism. Starting from 14 days from the beginning of exposure (FBE), O3 induced a leaf yellowing and a reduction of photosynthetic activity (-50%, in comparison with controls) due to both stomatal and mesophyll limitations (stomatal conductance: -52%; intercellular CO2 concentration: +11%). Membrane permeability was also impaired by O3-induced oxidative pressure (malondialdehyde: +27%). Plants tried to cope with such oxidative stress by (i) activating the antioxidant systems (e.g., ascorbic acid, glutathione), and (ii) regulating the phytohormone response. Despite an increased lipoxygenase activity occurred at 29 FBE (+61%), levels of jasmonic acid never changed, probably due to an antagonistic role played by ethylene (ET). Indeed, ET increased (+1.6-fold) from 22 days FBE until the end of exposure, also promoting the accumulation of salicylic acid (+73%). Abscisic acid increased throughout the whole experiment likely inducing stomatal closure. These outcomes suggest that the crosstalk between phytohormones played a central role in S. officinalis defense against O3
Spectral characterization of wheat functional trait responses to Hessian fly: Mechanisms for trait-based resistance
Full text linkInsect herbivores can manipulate host plants to inhibit defenses. Insects that induce plant galls are excellent examples of these interactions. The Hessian fly (HF, Mayetiola destructor) is a destructive pest of wheat (Triticum spp.) that occurs in nearly all wheat producing globally. Under compatible interactions (i.e., successful HF establishment), HF larvae alter host tissue physiology and morphology for their benefit, manifesting as the development of plant nutritive tissue that feeds the larva and ceases plant cell division and elongation. Under incompatible interactions (i.e., unsuccessful HF establishment), plants respond to larval feeding by killing the larva, permitting normal plant development. We used reflectance spectroscopy to characterize whole-plant functional trait responses during both compatible and incompatible interactions and related these findings with morphological and gene expression observations from earlier studies. Spectral models successfully characterized wheat foliar traits, with mean goodness of fit statistics of 0.84, 0.85, 0.94, and 0.69 and percent root mean square errors of 22, 10, 6, and 20%, respectively, for nitrogen and carbon concentrations, leaf mass per area, and total phenolic content. We found that larvae capable of generating compatible interactions successfully manipulated host plant chemical and morphological
composition to create a more hospitable environment. Incompatible interactions resulted in lower host plant nutritional quality, thicker leaves, and higher phenolic levels. Spectral measurements successfully characterized wheat responses to compatible and incompatible interactions, providing an excellent example of the utility of Spectral phenotyping in quantifying responses of specific plant functional traits associated with insect resistance
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