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Papers by antonio raschi

EGU General Assembly …, 2010

... 12, EGU2010-9034, 2010 EGU General Assembly 2010 © Author(s) 2010 CLIL takes action on climat... more ... 12, EGU2010-9034, 2010 EGU General Assembly 2010 © Author(s) 2010 CLIL takes action on climate change Sonia Caputo (1), Antonio Raschi (2), Danilo Marandola (2), and Francesca Ugolini (2) (1) IIS - Istituto d'Istruzione Superiore 'Alberti', Benevento, Italy (+39 0824 ...

Environmental and Experimental Botany, 1998

Long-term effects on and adaptations of the carbon physiology of long-lived trees exposed to incr... more Long-term effects on and adaptations of the carbon physiology of long-lived trees exposed to increasing atmospheric levels of CO 2 are unknown. We compared two indigenous Quercus species, Q. ilex and Q. pubescens, growing in a natural CO 2 spring located in central Italy and at a nearby control site. In May, 1995 photosynthetic rate at least doubled when measured with supplemental CO 2 in both species and sites. Dark respiration was much higher at the CO 2 spring site in both species. Foliar sugar and starch concentrations in Q. ilex exhibited significant site and diurnal differences (May and September). In July, 1995 there was little difference in the water potential values of the measured trees at the different sites over the diurnal period. Photosynthetic rate was higher for both species in the CO 2 spring, particularly in the early morning and late afternoon. Midday stomatal closure reduced photosynthesis to similar levels. In the morning leaf conductance and transpiration were generally lower in the CO 2 spring trees, contributing to higher instantaneous water use efficiency for both species. Isoprene emission rates were higher in Q. pubescens trees growing in the CO 2 spring. The maximum difference between control and CO 2 spring trees occurred in late afternoon. In contrast, Q. ilex exhibited isoprene emission near background level. Foliage and branch carbon and nitrogen status showed increased concentrations of starch and tannins in Q. ilex and of soluble sugars in Q. pubescens in the elevated CO 2 environment, while nitrogen concentration decreased in both species. Wood gravity increased 6 and 3% in Q. ilex and Q. pubescens, respectively, growing in the CO 2 spring. Q. ilex exhibited afternoon recovery of water potential compared to Q. pubescens which had better night-time recovery. Q. ilex and Q. pubescens exposed to elevated CO 2 for prolonged periods exhibit different mechanisms for dealing with additional reduced carbon and do maintain an altered carbon physiology, even in midst of the region's characteristic summer drought.

Ecosystems, 2008

Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems... more Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This study provides a synthesis of soil respiration (R s) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands. Maximum rates of R s (R s max), R s at a reference soil temperature (10°C; R s 10) and annual R s (estimated for 13 sites) ranged from 1.9 to 15.9 lmol CO 2 m-2 s-1 , 0.3 to 5.5 lmol CO 2 m-2 s-1 and 58 to 1988 g C m-2 y-1 , respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type of ecosystem. Across all sites R s max was closely related to R s 10 .

Ecological Modelling, 2002

The current work deals with the use in a Mediterranean environment of a simulation model of fores... more The current work deals with the use in a Mediterranean environment of a simulation model of forest ecosystem processes which was originally created for temperate areas (FOREST-BGC). The model was calibrated and applied on two deciduous forest stands in Tuscany (Central Italy) by using conventional and remote sensing data as inputs. First, information on the two stands needed to initialise the model was derived from different sources, while meteorological data were extrapolated from a nearby station by an existing procedure (MT-Clim). Temporal profiles of leaf area index (LAI) were then derived both from direct ground measurement and from the processing of NOAA-AVHRR NDVI data. The model was calibrated using stand transpiration values obtained for 1997 by a sap flow method. Next, its performances were tested against the same transpiration values measured in 1998. The results obtained indicate that FOREST-BGC is capable of simulating water fluxes of Mediterranean forests when suitable LAI profiles are considered. Moreover, the derivation of these profiles from NDVI data can improve the model performance probably due to an enhanced consideration of the effects of the typical Mediterranean summer water stress. These results support the final objective of the work, which is the development of a procedure capable of integrating conventional and remote sensing data to operationally simulate water and carbon fluxes on a regional scale.

Community Ecology, 2008

The effects of elevated atmospheric CO2 on in situ soil respiration and belowground biomass were ... more The effects of elevated atmospheric CO2 on in situ soil respiration and belowground biomass were studied in a FACE (Free Air CO2 Enrichment) facility. A Mediterranean grassland community was exposed to elevated and ambient CO2 concentrations in a mini-FACE system in Tuscany (Italy). We quantified litter mass and chemistry, root growth and turnover, CO2 efflux from soils, and soil microbial biomass. Elevated CO2 caused limited increases in aboveground production. Litter quality, fine root turnover, microbial biomass, root growth, and root biomass were not significantly affected by elevated CO2, except during some periods. Our results suggest that elevated atmospheric CO2 might moderately accelerate inputs of organic matter to soil carbon pools in Mediterranean grasslands, but it may also partially accelerate losses of carbon from belowground by stimulating soil respiration.

Community Ecology, 2008

... As a matter of fact, links between nutrient status, water bal-ance and activities of antioxid... more ... As a matter of fact, links between nutrient status, water bal-ance and activities of antioxidant enzymes of plants growing under elevated CO2 have been investigated, demonstrating that overall effects are often strictly interrelated and/or over-lapped (eg, Sgherri et al. 2000). ...

Chemosphere, 1998

Sap-flow of Quercus robur, Quercus petraea and Quercus cerris oak trees were studied.°'K radioiso... more Sap-flow of Quercus robur, Quercus petraea and Quercus cerris oak trees were studied.°'K radioisotope tracing, the heat pulse velocity technique and the Granier-method were employed. Numerous intense pulses were observed in healthy Quercus petraea superposing onto the usual diurnal change. Only a few pulses were observed in unhealthy Quercus petraea, in healthy Quercus cerris and healthy and unhealthy Quercus robur trees. Proportion of wet-wood assessed by y-and X-ray computer tomography and magnetic resonance imaging was significantly less in healthy Quercus petraea trees than in healthy Quercus cerris trees. Proportion of wet-wood was higher in healthy trees than unhealthy trees of both species .

Chemosphere, 1998

Our multidisciplmary research group has been engaged in studying the water transport traced by sh... more Our multidisciplmary research group has been engaged in studying the water transport traced by short half life cyclotron produced isotopes (24Na,43K) for many years in oak species. There are a lot of different methods to estimate quantitatively the sap flow in trees. Most of these are indirect, producing relative data. Our isotope labeling technique is the only one, offering direct velocity values. To interpret these results however are very difficult because it is impossible to estimate sap flow quantitatively without any information regarding the actual cross section through which this flow is carried on. The computer tomograph and magnetic resonance techniques can provide exact and quantitative information about the areas with high water content within the trunk. The first results suggest that not only the outermost layer of xylem, but also the other water rich compartments might play a decisive role in sap flow.

Chemosphere, 1998

The Bossoleto CO2 spring emits CO2 which has a stable carbon isotopic ratio (~5~3C =-8%o). We det... more The Bossoleto CO2 spring emits CO2 which has a stable carbon isotopic ratio (~5~3C =-8%o). We determined ~3C on leaves of several individual species growing in Bossoleto and in a nearby control site at ambient CO,.. ~5t3C was 6% more negative in leaves of species collected from the grassland community of Bossoleto, indicating increased discrimination (A) against the heavy carbon isotope. No such changes were found in ruderal species growing in the same spring, suggesting that photosynthetic capacity was much less affected. A was substantially increased under elevated CO2 in leaves of Quercus pubescens but not in Quercus ilex, which also did not show any increase in non-structural carbohydrates. Gas-exchange measurements made on Plantago lanceolata, supported the view that photosynthetic capacity is decreased in plants grown under elevated CO: and on poor soils.

Cereal Research Communications, 2005

Atmospheric Environment, 2004

ABSTRACT Quercus ilex and Quercus pubescens acorns were collected at two CO2 springs in Tuscany (... more ABSTRACT Quercus ilex and Quercus pubescens acorns were collected at two CO2 springs in Tuscany (Bossoleto and Viterbo, resp.). In addition to elevated CO2, these springs are a source of H2S and SO2. Acorns from a comparable field site distant from CO2 springs were used as controls. Acorns from CO2 springs contained significantly higher sulphur concentrations than controls (0.67 vs. 0.47mgg−1 dw in Q. ilex cotyledons and 1.01 vs. 0.80 in Q. pubescens) and, in Q. ilex, also more glutathione (1634 vs. 1393nmolg−1dw). When acorns were germinated and seedlings grown under ambient air conditions in the Botanical Garden in Graz for one year, leaves of Q. pubescens grown from CO2 spring acorns showed significantly higher S-concentrations than leaves grown from control acorns (2.27mgg−1 vs. 1.56mgg−1dw), and those of Q. ilex higher glutathione concentrations (929 vs. 462nmolg−1dw, CO2 spring vs. control acorns). One-year-old Q. ilex seedlings grown from CO2 spring acorns also showed elevated rates of chromosomal aberrations in root tips (a widely used test for environmental impacts), suggesting a permanent stress situation of the seedlings originating from the CO2 springs.

ABSTRACT In this study, for the year 2002, summer and winter thermohygrometric conditions of park... more ABSTRACT In this study, for the year 2002, summer and winter thermohygrometric conditions of parks with different surfaces, located in Florence (Italy), were analyzed in comparison to meteorological conditions recorded by a weather station located in the historic center of town. Thermal differences were related to the size and vegetation cover characteristics of the parks in question. Biometeorological indices were also applied to evaluate the effects of these different micrometeorological conditions on human well-being. The results showed that even small vegetated areas determine a decrease of air temperature even if this phenomenon is more evident for park size >2 ha. The nocturnal cooling of air temperatures both in summer and in winter was directly proportional to the size of the urban park. The results of the application of biometeorological indices confirmed the more comfortable microclimatic conditions of the parks, in comparison with the urban site, during summer and the less comfortable conditions during the winter period. In comparison to all the other green areas, the small vegetated courtyard (0.02 ha) studied showed the most comfortable microclimate highlighting the importance of this type of architectural element in urban areas to mitigate the effects of urban heat island during the summer season.

... Antonio Raschi*, Giuseppe Mario Lanini*, Francesca Ugolini*, Luigi Sanità di Toppi**, Laura B... more ... Antonio Raschi*, Giuseppe Mario Lanini*, Francesca Ugolini*, Luigi Sanità di Toppi**, Laura Bacci*, Marco Morabito*, Roberto Tognetti,***, Filippo Bussotti****. ... in which plants live are determined by the type of planting areas (peri-urban environment, urban parks, squares and ...

Agronomie, 1988

The research described in this paper was designed to define the stage of development during which... more The research described in this paper was designed to define the stage of development during which the excised embryo of maize acquires desiccation tolerance. The applied desiccation stress corresponded to a period of 2 days at 35 °C (during which the isolated embryos reached a water content around 3.8 %). The experiments led to the following conclusions : at stages where precocious germination is fully evident, the embryo can still be desiccation-intolerant ;-desiccation tolerance is acquired by the embryo at a very precise developmental stage, between 20 and 25 days after pollination (DAP) during which the dry weight increases by a I' ' .ctor of 5 to 10. In terms of DAP the onset of desiccation tolerance was found reproducible for 2 years and for the 4 genotypes tested. Normal development of the coleoptile and embryonic root originating from a dried embryo depends on the stage of excision : the younger the embryo is desiccated, the more abnormal are the coleoptile and the embryonic root originating from it. Acquisition of desiccation tolerance and of insensitivity of the embryo to desiccation damage is probably the result of two independent physiological processes : the first property is acquired rapidly and at earlier stages than the second. A set of proteins has been identified that is specifically expressed only at stages of development when the embryo is desiccation-tolerant. This may open possibilities for approaching the biochemistry of desiccation in the maize embryo.

Agriculture, Ecosystems & Environment, 2007

Tower CO 2 flux measurements from 20 European grasslands in the EUROGRASSFLUX data set covering a... more Tower CO 2 flux measurements from 20 European grasslands in the EUROGRASSFLUX data set covering a wide range of environmental and management conditions were analyzed with respect to their ecophysiological characteristics and CO 2 exchange (gross primary production, P g , and ecosystem respiration, R e) using light-response function analysis. Photosynthetically active radiation (Q) and top-soil temperature (T s) were identified as key factors controlling CO 2 exchange between grasslands and the atmosphere at the 30-min scale.

Agriculture, Ecosystems & Environment, 2007

... Article Outline. 1. Introduction 2. Materials and methods 2.1. Study sites 2.2. Nitrous oxide... more ... Article Outline. 1. Introduction 2. Materials and methods 2.1. Study sites 2.2. Nitrous oxide flux measurement techniques 3. Results and discussion 3.1. Spatial and temporal variability of N 2 O fluxes 3.2. Annual fluxes and emission factors 3.3. ...

Agriculture, Ecosystems & Environment, 1989

In this paper, the relationship between acoustic emission and freezing and thawing of plant tissu... more In this paper, the relationship between acoustic emission and freezing and thawing of plant tissues is investigated by means of ultrasound techniques. Ultrasound pulses were detected only after freezing. Ultrasound pulses of well-watered plants are negligible before the occurrence of freezing events that usually appear below-4 o C. Temperature lowering after freezing determines a sharp increase in ultrasound emission. The relationship between acoustic emission and the dehydration process caused by extracellular ice is discussed. From the preliminary observations reported, the ultrasound technique seems to be a useful tool for evaluating the occurrence of freezing stress in woody plants.

EGU General Assembly …, 2010

... 12, EGU2010-9034, 2010 EGU General Assembly 2010 © Author(s) 2010 CLIL takes action on climat... more ... 12, EGU2010-9034, 2010 EGU General Assembly 2010 © Author(s) 2010 CLIL takes action on climate change Sonia Caputo (1), Antonio Raschi (2), Danilo Marandola (2), and Francesca Ugolini (2) (1) IIS - Istituto d'Istruzione Superiore 'Alberti', Benevento, Italy (+39 0824 ...

Environmental and Experimental Botany, 1998

Long-term effects on and adaptations of the carbon physiology of long-lived trees exposed to incr... more Long-term effects on and adaptations of the carbon physiology of long-lived trees exposed to increasing atmospheric levels of CO 2 are unknown. We compared two indigenous Quercus species, Q. ilex and Q. pubescens, growing in a natural CO 2 spring located in central Italy and at a nearby control site. In May, 1995 photosynthetic rate at least doubled when measured with supplemental CO 2 in both species and sites. Dark respiration was much higher at the CO 2 spring site in both species. Foliar sugar and starch concentrations in Q. ilex exhibited significant site and diurnal differences (May and September). In July, 1995 there was little difference in the water potential values of the measured trees at the different sites over the diurnal period. Photosynthetic rate was higher for both species in the CO 2 spring, particularly in the early morning and late afternoon. Midday stomatal closure reduced photosynthesis to similar levels. In the morning leaf conductance and transpiration were generally lower in the CO 2 spring trees, contributing to higher instantaneous water use efficiency for both species. Isoprene emission rates were higher in Q. pubescens trees growing in the CO 2 spring. The maximum difference between control and CO 2 spring trees occurred in late afternoon. In contrast, Q. ilex exhibited isoprene emission near background level. Foliage and branch carbon and nitrogen status showed increased concentrations of starch and tannins in Q. ilex and of soluble sugars in Q. pubescens in the elevated CO 2 environment, while nitrogen concentration decreased in both species. Wood gravity increased 6 and 3% in Q. ilex and Q. pubescens, respectively, growing in the CO 2 spring. Q. ilex exhibited afternoon recovery of water potential compared to Q. pubescens which had better night-time recovery. Q. ilex and Q. pubescens exposed to elevated CO 2 for prolonged periods exhibit different mechanisms for dealing with additional reduced carbon and do maintain an altered carbon physiology, even in midst of the region's characteristic summer drought.

Ecosystems, 2008

Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems... more Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This study provides a synthesis of soil respiration (R s) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands. Maximum rates of R s (R s max), R s at a reference soil temperature (10°C; R s 10) and annual R s (estimated for 13 sites) ranged from 1.9 to 15.9 lmol CO 2 m-2 s-1 , 0.3 to 5.5 lmol CO 2 m-2 s-1 and 58 to 1988 g C m-2 y-1 , respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type of ecosystem. Across all sites R s max was closely related to R s 10 .

Ecological Modelling, 2002

The current work deals with the use in a Mediterranean environment of a simulation model of fores... more The current work deals with the use in a Mediterranean environment of a simulation model of forest ecosystem processes which was originally created for temperate areas (FOREST-BGC). The model was calibrated and applied on two deciduous forest stands in Tuscany (Central Italy) by using conventional and remote sensing data as inputs. First, information on the two stands needed to initialise the model was derived from different sources, while meteorological data were extrapolated from a nearby station by an existing procedure (MT-Clim). Temporal profiles of leaf area index (LAI) were then derived both from direct ground measurement and from the processing of NOAA-AVHRR NDVI data. The model was calibrated using stand transpiration values obtained for 1997 by a sap flow method. Next, its performances were tested against the same transpiration values measured in 1998. The results obtained indicate that FOREST-BGC is capable of simulating water fluxes of Mediterranean forests when suitable LAI profiles are considered. Moreover, the derivation of these profiles from NDVI data can improve the model performance probably due to an enhanced consideration of the effects of the typical Mediterranean summer water stress. These results support the final objective of the work, which is the development of a procedure capable of integrating conventional and remote sensing data to operationally simulate water and carbon fluxes on a regional scale.

Community Ecology, 2008

The effects of elevated atmospheric CO2 on in situ soil respiration and belowground biomass were ... more The effects of elevated atmospheric CO2 on in situ soil respiration and belowground biomass were studied in a FACE (Free Air CO2 Enrichment) facility. A Mediterranean grassland community was exposed to elevated and ambient CO2 concentrations in a mini-FACE system in Tuscany (Italy). We quantified litter mass and chemistry, root growth and turnover, CO2 efflux from soils, and soil microbial biomass. Elevated CO2 caused limited increases in aboveground production. Litter quality, fine root turnover, microbial biomass, root growth, and root biomass were not significantly affected by elevated CO2, except during some periods. Our results suggest that elevated atmospheric CO2 might moderately accelerate inputs of organic matter to soil carbon pools in Mediterranean grasslands, but it may also partially accelerate losses of carbon from belowground by stimulating soil respiration.

Community Ecology, 2008

... As a matter of fact, links between nutrient status, water bal-ance and activities of antioxid... more ... As a matter of fact, links between nutrient status, water bal-ance and activities of antioxidant enzymes of plants growing under elevated CO2 have been investigated, demonstrating that overall effects are often strictly interrelated and/or over-lapped (eg, Sgherri et al. 2000). ...

Chemosphere, 1998

Sap-flow of Quercus robur, Quercus petraea and Quercus cerris oak trees were studied.°'K radioiso... more Sap-flow of Quercus robur, Quercus petraea and Quercus cerris oak trees were studied.°'K radioisotope tracing, the heat pulse velocity technique and the Granier-method were employed. Numerous intense pulses were observed in healthy Quercus petraea superposing onto the usual diurnal change. Only a few pulses were observed in unhealthy Quercus petraea, in healthy Quercus cerris and healthy and unhealthy Quercus robur trees. Proportion of wet-wood assessed by y-and X-ray computer tomography and magnetic resonance imaging was significantly less in healthy Quercus petraea trees than in healthy Quercus cerris trees. Proportion of wet-wood was higher in healthy trees than unhealthy trees of both species .

Chemosphere, 1998

Our multidisciplmary research group has been engaged in studying the water transport traced by sh... more Our multidisciplmary research group has been engaged in studying the water transport traced by short half life cyclotron produced isotopes (24Na,43K) for many years in oak species. There are a lot of different methods to estimate quantitatively the sap flow in trees. Most of these are indirect, producing relative data. Our isotope labeling technique is the only one, offering direct velocity values. To interpret these results however are very difficult because it is impossible to estimate sap flow quantitatively without any information regarding the actual cross section through which this flow is carried on. The computer tomograph and magnetic resonance techniques can provide exact and quantitative information about the areas with high water content within the trunk. The first results suggest that not only the outermost layer of xylem, but also the other water rich compartments might play a decisive role in sap flow.

Chemosphere, 1998

The Bossoleto CO2 spring emits CO2 which has a stable carbon isotopic ratio (~5~3C =-8%o). We det... more The Bossoleto CO2 spring emits CO2 which has a stable carbon isotopic ratio (~5~3C =-8%o). We determined ~3C on leaves of several individual species growing in Bossoleto and in a nearby control site at ambient CO,.. ~5t3C was 6% more negative in leaves of species collected from the grassland community of Bossoleto, indicating increased discrimination (A) against the heavy carbon isotope. No such changes were found in ruderal species growing in the same spring, suggesting that photosynthetic capacity was much less affected. A was substantially increased under elevated CO2 in leaves of Quercus pubescens but not in Quercus ilex, which also did not show any increase in non-structural carbohydrates. Gas-exchange measurements made on Plantago lanceolata, supported the view that photosynthetic capacity is decreased in plants grown under elevated CO: and on poor soils.

Cereal Research Communications, 2005

Atmospheric Environment, 2004

ABSTRACT Quercus ilex and Quercus pubescens acorns were collected at two CO2 springs in Tuscany (... more ABSTRACT Quercus ilex and Quercus pubescens acorns were collected at two CO2 springs in Tuscany (Bossoleto and Viterbo, resp.). In addition to elevated CO2, these springs are a source of H2S and SO2. Acorns from a comparable field site distant from CO2 springs were used as controls. Acorns from CO2 springs contained significantly higher sulphur concentrations than controls (0.67 vs. 0.47mgg−1 dw in Q. ilex cotyledons and 1.01 vs. 0.80 in Q. pubescens) and, in Q. ilex, also more glutathione (1634 vs. 1393nmolg−1dw). When acorns were germinated and seedlings grown under ambient air conditions in the Botanical Garden in Graz for one year, leaves of Q. pubescens grown from CO2 spring acorns showed significantly higher S-concentrations than leaves grown from control acorns (2.27mgg−1 vs. 1.56mgg−1dw), and those of Q. ilex higher glutathione concentrations (929 vs. 462nmolg−1dw, CO2 spring vs. control acorns). One-year-old Q. ilex seedlings grown from CO2 spring acorns also showed elevated rates of chromosomal aberrations in root tips (a widely used test for environmental impacts), suggesting a permanent stress situation of the seedlings originating from the CO2 springs.

ABSTRACT In this study, for the year 2002, summer and winter thermohygrometric conditions of park... more ABSTRACT In this study, for the year 2002, summer and winter thermohygrometric conditions of parks with different surfaces, located in Florence (Italy), were analyzed in comparison to meteorological conditions recorded by a weather station located in the historic center of town. Thermal differences were related to the size and vegetation cover characteristics of the parks in question. Biometeorological indices were also applied to evaluate the effects of these different micrometeorological conditions on human well-being. The results showed that even small vegetated areas determine a decrease of air temperature even if this phenomenon is more evident for park size >2 ha. The nocturnal cooling of air temperatures both in summer and in winter was directly proportional to the size of the urban park. The results of the application of biometeorological indices confirmed the more comfortable microclimatic conditions of the parks, in comparison with the urban site, during summer and the less comfortable conditions during the winter period. In comparison to all the other green areas, the small vegetated courtyard (0.02 ha) studied showed the most comfortable microclimate highlighting the importance of this type of architectural element in urban areas to mitigate the effects of urban heat island during the summer season.

... Antonio Raschi*, Giuseppe Mario Lanini*, Francesca Ugolini*, Luigi Sanità di Toppi**, Laura B... more ... Antonio Raschi*, Giuseppe Mario Lanini*, Francesca Ugolini*, Luigi Sanità di Toppi**, Laura Bacci*, Marco Morabito*, Roberto Tognetti,***, Filippo Bussotti****. ... in which plants live are determined by the type of planting areas (peri-urban environment, urban parks, squares and ...

Agronomie, 1988

The research described in this paper was designed to define the stage of development during which... more The research described in this paper was designed to define the stage of development during which the excised embryo of maize acquires desiccation tolerance. The applied desiccation stress corresponded to a period of 2 days at 35 °C (during which the isolated embryos reached a water content around 3.8 %). The experiments led to the following conclusions : at stages where precocious germination is fully evident, the embryo can still be desiccation-intolerant ;-desiccation tolerance is acquired by the embryo at a very precise developmental stage, between 20 and 25 days after pollination (DAP) during which the dry weight increases by a I' ' .ctor of 5 to 10. In terms of DAP the onset of desiccation tolerance was found reproducible for 2 years and for the 4 genotypes tested. Normal development of the coleoptile and embryonic root originating from a dried embryo depends on the stage of excision : the younger the embryo is desiccated, the more abnormal are the coleoptile and the embryonic root originating from it. Acquisition of desiccation tolerance and of insensitivity of the embryo to desiccation damage is probably the result of two independent physiological processes : the first property is acquired rapidly and at earlier stages than the second. A set of proteins has been identified that is specifically expressed only at stages of development when the embryo is desiccation-tolerant. This may open possibilities for approaching the biochemistry of desiccation in the maize embryo.

Agriculture, Ecosystems & Environment, 2007

Tower CO 2 flux measurements from 20 European grasslands in the EUROGRASSFLUX data set covering a... more Tower CO 2 flux measurements from 20 European grasslands in the EUROGRASSFLUX data set covering a wide range of environmental and management conditions were analyzed with respect to their ecophysiological characteristics and CO 2 exchange (gross primary production, P g , and ecosystem respiration, R e) using light-response function analysis. Photosynthetically active radiation (Q) and top-soil temperature (T s) were identified as key factors controlling CO 2 exchange between grasslands and the atmosphere at the 30-min scale.

Agriculture, Ecosystems & Environment, 2007

... Article Outline. 1. Introduction 2. Materials and methods 2.1. Study sites 2.2. Nitrous oxide... more ... Article Outline. 1. Introduction 2. Materials and methods 2.1. Study sites 2.2. Nitrous oxide flux measurement techniques 3. Results and discussion 3.1. Spatial and temporal variability of N 2 O fluxes 3.2. Annual fluxes and emission factors 3.3. ...

Agriculture, Ecosystems & Environment, 1989

In this paper, the relationship between acoustic emission and freezing and thawing of plant tissu... more In this paper, the relationship between acoustic emission and freezing and thawing of plant tissues is investigated by means of ultrasound techniques. Ultrasound pulses were detected only after freezing. Ultrasound pulses of well-watered plants are negligible before the occurrence of freezing events that usually appear below-4 o C. Temperature lowering after freezing determines a sharp increase in ultrasound emission. The relationship between acoustic emission and the dehydration process caused by extracellular ice is discussed. From the preliminary observations reported, the ultrasound technique seems to be a useful tool for evaluating the occurrence of freezing stress in woody plants.