1,720,989 research outputs found
Role of membrane transport in salt stress resistence in aeroponnically-grown olive genotypes
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Trees in the urban environment : response mechanisms and benefits for the ecosystem should guide plant selection for future plantings
No full textIt is well known that, at present, more than a half of the world population live in the built-up areas (in Europe almost 80%) and the urbanization trend will continue as the population increases and more people will live in large cities. In this scenario arboriculture and urban forestry should have a main role in the effort to manage urbanization and to create livable cities and it is certain that all green areas, starting from the single tree specimens to periurban forests which, in some way, recall the "concept of nature", can fulfil a paramount function in improving life quality and in reaching the minimal threshold for human well-being. What is going to happen next - over 10-15 years - will obviously be of the greatest interest to all people concerned with urban environment. This latter poses some constraints to tree growth and survival: drought, poor soil quality and compaction, pollutants, salinity, pathogens, light heterogeneity, and conflicts with human activities often cause premature plant death or limit plant growth, thus reducing the net benefit by urban green areas. It is therefore important to better understand the dynamics leading to tree decline in the urban environment, and to develop strategies and techniques aimed at improving the horticultural tolerance (i.e. the capacity to provide benefits, not only to survive, under stressful conditions) of urban trees. These include nursery pre-conditioning techniques and post-planting management techniques, but a key role is played by species selection. Hundreds of species are used in the urban environment, but selection criteria are frequently based upon aesthetics and whether the species are native or not, rather than on the tolerance to typical stresses imposed by the built environment and on the capacity to provide substantial benefits therein
New evidence for the functional roles of volatile and non-volatile isoprenoids in stressed plants
No full textMediterranean plants are challenged against extreme, often unpredictable stress events which may pose severe constrains for the plant survival, as uncontrolled reactive oxygen species (ROS) generation ultimately lead to cell death. Secondary metabolites, which are highly responsive to environmental drivers, constitute a flexible system aimed at countering drastic perturbations in the cellular ROS homeostasis. Recent evidence supports the notion of isoprenoids (products of methylerythriol phosphate (MEP) pathway) as aimed at quenching ROS, not only devoted at avoiding ROS formation. Here we focus our attention on "essential isoprenoids" (i.e., carotenoids) and "non-essential isoprenoids" (e.g., isoprene), and how they constitute a well-coordinated system aimed at countering an excess of radiant energy to the chloroplast during stress progression. We also offer recent evidences of the functional roles of the end-product of MEP pathway, abscisic acid, as an essential regulator of the whole-plant metabolic machinery, and not merely of stomatal opening
Water relations, growth, and leaf gas exchange as affected by water stress in Jatropha curcas
No full textHere we examined the response mechanisms and the strategies adopted to cope with drought stress in Jatropha curcas L. Response mechanisms to water stress were explored in three different accessions (from Brazil, Tanzania and Suriname) of J. curcas in terms of water and osmotic relations, gas exchange, PSII photochemistry, and growth performances. Plants were exposed to 18 days of water stress (irrigation was kept at 20% of water holding capacity) followed by 13 days of relief from stress. J. curcas withstands drought stress with a drought-avoidance mechanism through a water saving strategy. These responses include selective abscission of leaves, and marked decreases in net photosynthetic rates and water use efficiency. This allows plants to maintain an " above-lethal" water potential during stress, and to recover net assimilation rate promptly when water availability to the roots is resumed. The Suriname accession displayed greater reductions in net photosynthesis, maximal efficiency of PSII photochemistry (Fv/Fm), total leaf area and plant dry weight, as compared with both Tanzania and, particularly, the Brazil accession, during drought stress. Impairment of PSII photochemistry was also observed in the Suriname accession at the end of the relief period. Water-stressed J. curcas, irrespective of seed source, was capable to recover net photosynthesis to the level of the well watered counterparts by the end of the relief period. Our data allow to conclude that J. curcas may survive to drought spells of moderate intensities but, at the same time pose serious concerns for its profitable cultivation in arid/semi-arid regions worldwide
Mesophyll conductance plays a central role in leaf functioning of Oleaceae species exposed to contrasting sunlight irradiance
No full textThe ability to modify mesophyll conductance (gm) in response to changes in irradiance may be a component of the acclimation of plants to shade-sun transitions, thus influencing species-specific distributions along light-gradients, and the ecological niches for the different species. To test this hypothesis we grew three woody species of the Oleaceae family, the evergreen Phillyrea latifolia (sun-requiring), the deciduous Fraxinus ornus (facultative sun-requiring) and the hemi-deciduous Ligustrum vulgare (shade tolerant) at 30 or 100% sunlight irradiance. We show that neither mesophyll conductance calculated with combined gas exchange and chlorophyll fluorescence techniques (gm) nor CO2 assimilation significantly varied in F. ornus because of sunlight irradiance. This corroborates previous suggestions that species with high plasticity for light requirements, do not need to undertake extensive reorganization of leaf conductances to CO2 diffusion to adapt to different light environments. On the other hand, gm steeply declined in L. vulgare and increased in P. latifolia exposed to full-sun conditions. In these two species, leaf anatomical traits are in part responsible for light-driven changes in gm, as revealed by the correlation between gm and mesophyll conductance estimated by anatomical parameters (gmA). Nonetheless, gm was greatly overestimated by gmA when leaf metabolism was impaired because of severe light stress. We show that gm is maximum at the light intensity at which plant species have evolved and we conclude that gm actually plays a key role in the sun and shade adaptation of Mediterranean species. The limits of gmA in predicting mesophyll conductance are also highlighted
Editorial: Plants' Responses to Novel Environmental Pressures
Full text linkPlants have been exposed to multiple environmental stressors on long-term (seasonal) and short-term (daily) basis since their appearance on land. During the last decades, however, plants have been frequently exposed to sudden changes in their environment (imposed by global change) which indeed involves the acclimation/adaptation syndrome of living organisms. The frequency of these unpredictable ‘stress’ events is expected to increase further in the near future. Such severe, even transient alterations in environmental stimuli (variables) represent new challenges to plants, which do not possess the ‘flight’ strategy usually displayed by other organisms.
Plants have developed, however, a multiplicity of highly integrated adjustments, involving morpho-anatomical, physiological and biochemical traits, to cope with challenges imposed by novel, harsher environments: these constitute the ‘flight strategy of sessile organisms’. Interestingly, several habitats threatened by the novel stresses are biodiversity hotspots. For example, Mediterranean basin, in which high light growing plants face heat waves coupled with the scarcity of rainfall of increasing frequency and severity, represents just 2% of the earth’s land area, but account for 16% of the world’s plant species. This implies that plants have been and are capable to display a wide range of acclimation/adaptation strategies to cope with most unfavorable environments. Nonetheless, the unpreceded rate at which climate changes may exceed the capacity of plants to acclimate and adapt successfully to the novel environmental pressures, further exacerbated by an increase in anthropogenic pressure.
Understanding the mechanisms through which plants respond to new challenges posed by the concurrent effect of different stress agents is crucial, as obvious, to develop strategies of biodiversity conservation and ecosystem functionality. This is exactly the focus of this Research Topic. Review, Opinion as well as Original Research articles are welcome covering basic and applied research on plant functioning under adverse environmental conditions. The frequency of extreme stress events, mostly due to the concurrent effects of different stressors, is increasing particularly in the arid and semi-arid regions, which represent indeed among the most fragile ecosystems worldwide. Papers dealing with the effects of multiple stress agents on plant functioning are, therefore, particularly welcome. We are, however, also interested to receive contributions dissecting response mechanisms (from molecular to organism and whole-plant levels) of plants to a wide range of individual stressors, with a view to a rapidly changing climate, covering plant responses from other regions of the world. These include, but are not limited to drought and heat stress, excess light stress (including UV radiation), cold, ozone and rising CO2 concentration, and their combinations. Theories that predict the plant behavior, acclimation and plant plasticity are also inside the scope of this topi
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
Isoprene Responses and Functions in Plants Challenged by Environmental Pressures Associated to Climate Change
Full text linkThe functional reasons for isoprene emission are still a matter of hot debate. It was hypothesized that isoprene biosynthesis evolved as an ancestral mechanism in plants adapted to high water availability, to cope with transient and recurrent oxidative stresses during their water-to-land transition. There is a tight association between isoprene emission and species hygrophily, suggesting that isoprene emission may be a favorable trait to cope with occasional exposure to stresses in mesic environments. The suite of morpho-anatomical traits does not allow a conservative water use in hygrophilic mesophytes challenged by the environmental pressures imposed or exacerbated by drought and heat stress. There is evidence that in stressed plants the biosynthesis of isoprene is uncoupled from photosynthesis. Because the biosynthesis of isoprene is costly, the great investment of carbon and energy into isoprene must have relevant functional reasons. Isoprene is effective in preserving the integrity of thylakoid membranes, not only through direct interaction with their lipid acyl chains, but also by up-regulating proteins associated with photosynthetic complexes and enhancing the biosynthesis of relevant membrane components, such as mono- and di-galactosyl-diacyl glycerols and unsaturated fatty acids. Isoprene may additionally protect photosynthetic membranes by scavenging reactive oxygen species. Here we explore the mode of actions and the potential significance of isoprene in the response of hygrophilic plants when challenged by severe stress conditions associated to rapid climate change in temperate climates, with special emphasis to the concomitant effect of drought and heat. We suggest that isoprene emission may be not a good estimate for its biosynthesis and concentration in severely droughted leaves, being the internal concentration of isoprene the important trait for stress protection
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