1,721,049 research outputs found
A mechanistic understanding of ozone impact on forest ecosystems.
No full textChanges in air chemistry and subsequent physical changes in the environment have a profound effect on the classic "disease triangle". Environmental factors alter ecosystem health and host susceptibility to biotic and abiotic stress. Plant response to various disease-causing stressors can be changed through introducing ozone (O3) into the system. These effects are variable, depending on the timing, intensity and order of the exposure. It is well known that O3 may produce on a plant functional alterations even without, before the onset of, or in addition, to macroscopic effects. Plants are able to respond to O3: several potential mechanisms comprehending exclusion, tolerance, compensation and repair may work simultaneously to create a complex signaling network. These include changes in photosynthesis, cellular redox homeostasis, perception by apoplastic proteins, oxidative damage to membranes, hormonal regulation of the lesion formation, modulation of osmoprotectants and activation of enzymatic and non-enzymatic antioxidant systems. Within a single species, differences in structural, functional and transcriptional traits may play importante roles in adaptation/acclimation to environments characterized by high oxidative pressure. Functional traits can predict plant behavior in its natural environmental and have been correlated to the degree of tolerance to oxidative stress. The science to accurately descrive how O3 affects plants and ecosystems in a changing climate is of paramount importance to guide political decision making
Biological monitoring of ozone pollution with vascular plants
No full textBiological monitoring (BM) uses organisms to determine the presence, amounts, temporal/spatial changes, and effects of both abiotic and biotic factors in the environment. The huge difference between BM and traditional physico-chemical measures of air quality is that the latter measures take into account emissions and immissions but only indirectly measure the “health” of the atmosphere because they do not look directly at biological responses. Specific plants, and namely tobacco cv. Bel-W3 are considered to be reliable bioindicators of ambient ozone (O3). Leaf injury on these plants is usually the first indication that a region has developed an O3 problem. Bel-W3 tobacco is a “perfect” bioindicator of O3 in the air, as it is highly sensitive. It develops easily recognizable and quantifiable peculiar foliar symptoms, and its vegetative period is coincident with the photo-smog season. Biomonitoring protocols are
applied in community, local, regional, and nation-wide campaigns. The entire methodology, from plant cultivation to exposure, injury assessment, data treatment, statistical analysis, and presentation of results, is now standardized. Some sticking points are that: (i) BM does not replace modeling or
conventional methods of direct measurement of air pollutants, it complements them by demonstrating the biological effect; (ii) bioindicator stations can make it possible to supplement at moderate costs the pre-existing network; and (iii) bioindicators raise public awareness by recourse to living organisms (i.e., O3-sensitive plants make invisible air pollution visible)
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
Lichen distribution and bioindicator tobacco plants give discordant response: a case study from Italy
No full textEpiphytic lichen biodiversity (LB) distribution was evaluated in a 1000 km2 area in Tuscany (Central Italy). In the same area, a survey was performed to monitor tropospheric ozone (O3) phytotoxic effects using tobacco plants (Nicotiana tabacum) cv. Bel-W3 (O3 supersensitive) and cv. Bel-B (O3 resistant) as bioindicators. The LB proved to be negatively correlated with ambient levels of nitrogen oxides, particulate and carbon monoxide, but not with benzene. LB spatial distribution followed a peculiar trend, with highest values in areas with low population density. Data from an O3 analyser set in evidence a typical circadian profile, confirming the photochemical nature of this pollutant. Quite high nocturnal values along the coast were related to the presence of surrounding mountains which constrained the back-and-forth flow of the air in sea breezes. Long- and short-term phytotoxicity critical levels for O3 were systematically trespassed. Bel-W3 tobacco was always affected in every site involved in the study; average O3 injury distribution was greater in rural areas; tobacco response was positively correlated to several O3 descriptors with second-order functions. Correlation analysis failed to demonstrate any association between lichen and tobacco data, due to the fact that LB values were higher in inland zones, far from the main urban and industrial areas, where instead damage to tobacco plants was generally lower. It is concluded that the lichen biodiversity is not suitable for monitoring O3 levels, at least in the study area
Leaves of Lolium multiflorum as indicators of airborne trace element distribution in central Italy
No full textAmbient air contains particles, ranging from sub-micrometric aerosols to clearly visible dust and sand grains. Plants during evolution developed the ability to maximise light interception and CO2 assimilation and also the efficiency to collect the airborne pollutants. Therefore, plant tissues have been used as indicators of trace elements air pollution. Lolium multiflorum leaves were used as a sampler to describe the distribution of selected elements in the area of Carrara (Tuscany, Central Italy). Unwashed healthy leaves collected in September 2007 from nine sampling sites were analysed by ICP-MS. Enrichment factors (EFs) were calculated taking Al as crustal reference element. Cd and Mo exhibited the highest EFs, with some values above 10,000. Varimax rotated factor analysis identified three main source groups of elements, namely crustal components, marine aerosol spray nd anthropogenic sources
Effetti protettivi dal danno da ossidanti in tessuti fogliari colonizzati da parassiti biotrofi e necrotrofi.
No full textDefense 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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