Soil sealing is one of the most pervasive forms of soil degradation that follows urbanization and, despite innovative pavements (i.e. pervious) are being installed in urban areas to mitigate it, ...there is little research on the effects of pervious pavements on soil water and carbon cycle and on the physiology of urban trees. The aim of this 4-year experiment was to assess the effects of three pavements, differing in permeability to water and gases, on some soil physical parameters, and on growth and physiology of newly planted Celtis australis and Fraxinus ornus. Treatments were: 1) impermeable pavement (asphalt on concrete sub-base); 2) permeable pavement (pavers on crushed rock sub-base); 3) porous design (porous pavement on crushed rock sub-base); 4) control (unpaved soil, kept free of weed by chemical control). Soil (temperature, moisture, oxygen content and CO2 efflux) and plant (above- and below-ground growth, leaf gas exchange, chlorophyll fluorescence, water relations) parameters were measured.
All types of pavements altered the water cycle compared to unpaved soil plots, but this disturbance was less intense in porous pavements than in other soil cover types. Porous pavements allowed both higher infiltration and evaporation of water than both pavers and asphalt. Reduction of evaporative cooling from soil paved with permeable and impermeable pavements contributed to significant soil warming: at 20cm depth, soils under concrete pavers and asphalt were 4 and 5°C warmer than soil covered by porous pavements and unpaved soils, respectively. Thus, enhancing evaporation from paved soil by the use of porous pavements may contribute to mitigating urban heat islands. CO2 greatly accumulated under impermeable and permeable pavements, but not under porous pavements, which showed CO2 efflux rates similar to control. Soil oxygen slightly decreased only beneath asphalt.
Growth of newly planted C. australis and F. ornus was little affected by pavement type. Tree transpiration rapidly depleted soil moisture compared to the not-planted scenario, but soil moisture did not fall below wilting point (particularly in the deeper soil layers, i.e. 40–50cm) in any treatment. While C. australis showed similar leaf gas exchange and water relations in all treatments, F. ornus showed a depression in CO2 assimilation and slight signs of stress of the photosynthetic apparatus when planted in soil covered with impermeable pavement.
The effects of soil cover with different materials on tree growth and physiology were little, because newly planted trees have most of their roots still confined in the unpaved planting pit. Still, the reduction of soil sealing around the planting pit triggered the establishment of sensitive species such as ash. Further research is needed to assess the effects of different pavement types on established, larger trees.
•Soil sealing depresses water and carbon exchange between soil and the atmosphere.•As a consequence of reduced evaporation, warming occurs in sealed soils.•Disturbance to element cycling can be mitigated by the use of porous pavements.•Tree responses to pavements is species-specific, but generally little for establishing trees.
Leaf deposition of PM10–100, PM2.5–10, PM0.2–2.5 and of 21 elements was investigated in a roadside vegetation barrier formed by i) two evergreen shrub species (Photinia × fraseri, Viburnum lucidum), ...with ii) two planting densities (0.5, 1.0 plant m−2), at iii) three distances from the road (2.0, 5.5, 9.0 m), at iv) two heights from the ground (1.5, 3.0 m), and on v) three dates (Aug, Sep, Oct).
The presence of black and brown on-leaf PM10–100 and their element composition were detected by microscopy and image analysis. Pollutant deposition was also measured using passive samplers at five distances from the road (2.0, 5.5, 9.0, 12.5, 19.5 m) in the area of the barrier and in an adjacent lawn area.
V. lucidum had more PM2.5–10 and PM0.2–2.5 on leaves than P. × fraseri, while most elements were higher in P. × fraseri. Most pollutants decreased at increasing distances from the road and were higher at 1.5 m from the ground compared to 3.0 m.
Higher planting density in P. × fraseri enhanced the deposition of PM10–100 and PM2.5–10, while in V. lucidum, the planting density did not affect the depositions.
Black PM10–100 decreased a long distance from the road and was entirely composed of carbon and oxygen, which was thus identified as black carbon from fuel combustion.
The vegetation barrier had a higher deposition of most PM fractions at 5.5–12.5 m, while in the lawn area, depositions did not change. At 19.5 m, the PM10–100 was 32% lower behind the barrier than in the lawn area. In conclusion, the vegetation barrier changed the deposition dynamics of pollutants compared to the lawn area. These results strengthen the role of vegetation barriers and shrub species against air pollution and may offer interesting insights for the use of new road green infrastructures to improve air quality.
Display omitted
•Higher LAI induced higher deposition, while planting density was not a determinant.•Vegetation barrier changed deposition dynamics in the experimental site.•Image analysis differentiated between on-leaf PM with different colorations.•On-leaf PM with different colorations had a different element composition.
Climate change is impairing tree physiology and growth, causing an increase in tree dieback in many Mediterranean forests. These desiccation phenomena are leading to changes in land cover and plant ...community composition. Mediterranean plants are capable to emit large amount of Biogenic Volatile Organic Compounds (BVOCs), whose emission and biosynthesis is strongly affected by environmental conditions. This study evaluates the seasonal changes in understory species composition in two forest stands in Southern Tuscany characterized by different levels of Quercus ilex L. crown defoliation (low and high defoliation, LD and HD) and the relationship with BVOCs emissions over three years. We found significant changes in the understory plant community following Q. ilex crown defoliation and mortality, observing an increment in the number of shrubs both in HD and LD stands. The environmental sampling of BVOCs fully reflected the changes in vegetation cover and composition, with a reduction in the amount of monoterpene emissions due to the increasing rates of defoliation and mortality of Q. ilex trees. Our results suggest that terpene emissions from Mediterranean forests would be modified by an increase of Q. ilex dieback, with important consequences for functioning of this forest ecosystem and its atmospheric chemistry.
Display omitted
•A widespread dieback of Quercus ilex has been recently observed in Mediterranean forests.•Holm oak dieback is affecting the forest structure favouring the expansion of shrub species.•Changes in understory plants are reflected in BVOC emissions at atmospheric level.
Ghrelin in Central Neurons Ferrini, F; Salio, C; Lossi, L ...
Current neuropharmacology,
03/2009, Letnik:
7, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Ghrelin, an orexigenic peptide synthesized by endocrine cells of the gastric mucosa, is released in the bloodstream in response to a negative energetic status. Since discovery, the hypothalamus was ...identified as the main source of ghrelin in the CNS, and effects of the peptide have been mainly observed in this area of the brain. In recent years, an increasing number of studies have reported ghrelin synthesis and effects in specific populations of neurons also outside the hypothalamus. Thus, ghrelin activity has been described in midbrain, hindbrain, hippocampus, and spinal cord. The spectrum of functions and biological effects produced by the peptide on central neurons is remarkably wide and complex. It ranges from modulation of membrane excitability, to control of neurotransmitter release, neuronal gene expression, and neuronal survival and proliferation. There is not at present a general consensus concerning the source of ghrelin acting on central neurons. Whereas it is widely accepted that the hypothalamus represents the most important endogenous source of the hormone in CNS, the existence of extra-hypothalamic ghrelin-synthesizing neurons is still controversial. In addition, circulating ghrelin can theoretically be another natural ligand for central ghrelin receptors. This paper gives an overview on the distribution of ghrelin and its receptor across the CNS and critically analyses the data available so far as regarding the effects of ghrelin on central neurotransmission.
BDNF as a pain modulator Merighi, Adalberto; Salio, Chiara; Ghirri, Alessia ...
Progress in neurobiology,
07/2008, Letnik:
85, Številka:
3
Journal Article
Recenzirano
Odprti dostop
At least some neurotrophins may be powerful modulators of synapses, thereby influencing short- and long-term synaptic efficiency. BDNF acts at central synapses in pain pathways both at spinal and ...supraspinal levels. Neuronal synthesis, subcellular storage/co-storage and release of BDNF at these synapses have been characterized on anatomical and physiological grounds, in parallel with trkB (the high affinity BDNF receptor) distribution. Histological and functional evidence has been provided, mainly from studies on acute slices and intact animals, that BDNF modulates fast excitatory (glutamatergic) and inhibitory (GABAergic/glycinergic) signals, as well as slow peptidergic neurotrasmission in spinal cord. Recent studies have unraveled some of the neuronal circuitries and mechanisms involved, highlighting the key role of synaptic glomeruli in lamina II as the main sites for such a modulation.
Here 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.
► Jatropha curcas responds to water stress with an avoidance through water-saving mechanism. ► Basis of this mechanism are early stomatal closure and leaf shedding. ► Different sources showed different tolerance to water stress. ► Genetic differences were found and conformed to the physiological differences.
•Pruning method, not only its intensity, modulates the tree response to pruning.•Reducing the apical growing axis to a lateral little disturbs branch growth.•Topping increases codominance and weakens ...branch structure.•In topping, higher Vc,max and Jmax are not paralleled by higher CO2 assimilation.
The aim of this work was to evaluate the effects of repeated pruning interventions using different pruning methods on growth and physiology of Acer pseudoplatanus L. Trees were pruned in 2008 and 2010 according to widely used pruning techniques for urban trees, such as reduction cut, removal cut and heading (topping) cut. Crown dieback, growth of the plant and of the pruned branches, leaf morphological traits and leaf gas exchange were assessed during the two growing seasons after each pruning cycle. Topping cut (i.e. the pruning treatment which suppressed the primary axis without providing a substitute) induced changes on tree growth pattern (i.e. by increasing the release of adventitious watersprouts and root suckers and decreasing stem diameter growth), which were not observed in the other pruning treatments. At the leaf level only topping cut increased leaf area at the expense of leaf mass per area, which may contribute to explain the higher occurrence of dieback on topped branches than in control and in the other pruning treatments. Also, leaves on topped branches displayed higher chlorophyll content and higher activity of Calvin cycle enzymes, which did not translate in higher CO2 assimilation. We show here that pruning method, not only its severity (i.e. the amount of leaf area removed), modulates the morpho-physiological response of trees to pruning and that maintenance of apical control and apical dominance are key issues to preserve a structurally sound tree structure, as well as the long-term efficiency of the photosynthetic apparatus.
Sensory neurons in dorsal root ganglia (DRGs) are the first-order neurons along the pathway conveying sensory information from the periphery to the central nervous system. The analysis of the ...morphological and physiological features of these neurons and their alterations in pathology is the necessary prerequisite to understand pain encoding mechanisms. Here, we describe an in vitro procedure for combined morphofunctional analysis of mouse DRGs. Freshly excised DRGs obtained from adult mice were incubated in collagenase to dissolve the ensheathing connective capsule. The degradation of the connective tissue facilitates both access to the neurons by classical recording glass pipettes and the penetration of primary antibodies for immunohistochemical procedures. The entire DRGs were then imaged using a confocal microscope obtaining a fine 3D representation of their cytoarchitecture without requiring tissue sectioning. Thus, our proposed whole-mount preparation represents a flexible in vitro approach for both functional and phenotypic analysis of DRG neurons by at the same time preserving their neuroanatomical relationships.
This experiment was carried out to evaluate the early physiological and growth response of two shade trees to root damage. European limes (Tilia × europea) and horse chestnuts (Aesculus ...hippocastanum) were planted in March 2004 and allowed to establish undisturbed for 5 years. In 2009, roots were damaged by either excavating one (MD) or two (SD) trenches at 40 cm from the root flare. Roots were excavated with an AirspadeTM to evaluate root loss caused by trenching. Shoot and diameter growth, leaf gas exchange, chlorophyll fluorescence and leaf water relations were determined up to 26 months after root severance. Results indicate that the growth reduction normally occurring after construction damage is due to reduced leaf gas exchange and less favorable water relations. Also, signs of photoinhibition were found in SD plants, particularly in horse chestnut. Therefore, root loss through trenching induced a mild water stress to severed trees, even in years characterized by high rainfall and water availability. More observations are needed to determine whether trees will be able to recover from damage or will decline further, especially if dryer years will occur before complete root regeneration.
PDF
