Yasutomo Hoshika - Academia.edu (original) (raw)

Papers by Yasutomo Hoshika

Research paper thumbnail of Stress markers and physiochemical responses of the Mediterranean shrub Phillyrea angustifolia under current and future drought and ozone scenarios

Research paper thumbnail of Exposure- and flux-based assessment of ozone risk to sugarcane plants

Research paper thumbnail of Ozone impairs the response of isoprene emission to foliar nitrogen and phosphorus in poplar

Research paper thumbnail of Hyperspectral Reflectance of Light-Adapted Leaves Can Predict Both Dark- and Light-Adapted Chl Fluorescence Parameters, and the Effects of Chronic Ozone Exposure on Date Palm (Phoenix dactylifera)

International Journal of Molecular Sciences

High-throughput and large-scale measurements of chlorophyll a fluorescence (ChlF) are of great in... more High-throughput and large-scale measurements of chlorophyll a fluorescence (ChlF) are of great interest to investigate the photosynthetic performance of plants in the field. Here, we tested the capability to rapidly, precisely, and simultaneously estimate the number of pulse-amplitude-modulation ChlF parameters commonly calculated from both dark- and light-adapted leaves (an operation which usually takes tens of minutes) from the reflectance of hyperspectral data collected on light-adapted leaves of date palm seedlings chronically exposed in a FACE facility to three ozone (O3) concentrations (ambient air, AA; target 1.5 × AA O3, named as moderate O3, MO; target 2 × AA O3, named as elevated O3, EO) for 75 consecutive days. Leaf spectral measurements were paired with reference measurements of ChlF, and predictive spectral models were constructed using partial least squares regression. Most of the ChlF parameters were well predicted by spectroscopic models (average model goodness-of-fi...

Research paper thumbnail of Isotopic and Water Relation Responses to Ozone and Water Stress in Seedlings of Three Oak Species with Different Adaptation Strategies

Forests

The impact of global changes on forest ecosystem processes is based on the species-specific respo... more The impact of global changes on forest ecosystem processes is based on the species-specific responses of trees to the combined effect of multiple stressors and the capacity of each species to acclimate and cope with the environment modification. Combined environmental constraints can severely affect plant and ecological processes involved in plant functionality. This study provides novel insights into the impact of a simultaneous pairing of abiotic stresses (i.e., water and ozone (O3) stress) on the responses of oak species. Water stress (using 40 and 100% of soil water content at field capacity—WS and WW treatments, respectively) and O3 exposure (1.0, 1.2, and 1.4 times the ambient concentration—AA, 1.2AA, and 1.4AA, respectively) were carried out on Quercus robur L., Quercus ilex L., and Quercus pubescens Willd. seedlings, to study physiological traits (1. isotope signature [δ13C, δ18O and δ15N], 2. water relation [leaf water potential, leaf water content], 3. leaf gas exchange [l...

Research paper thumbnail of Developing Ozone Risk Assessment for Larch Species

Frontiers in Forests and Global Change

Ozone (O3) risk assessment for the protection of forests requires species-specific critical level... more Ozone (O3) risk assessment for the protection of forests requires species-specific critical levels (CLs), based on either O3 concentrations (AOT40) or stomatal uptake (PODY) accumulation over the growing season. Larch (Larix sp.) is a genus with O3-susceptible species, widely distributed in the northern hemisphere and with global economic importance. We analyzed published and unpublished data of Japanese larch (Larix kaempferi) and its hybrid F1 (Larix gmelinii var. japonica × L. kaempferi) stomatal responses for developing a parameterization of stomatal conductance model and estimating PODY-based CLs with two Y thresholds, that is, 0 and 1 nmol m–2 s–1 projected leaf area (PLA). In parallel, we estimated AOT40-based CLs. The results show that the AOT40-based CLs for a 2% and 4% biomass loss in Japanese larch were 5.79 and 11.59 ppm h, that is, higher than those in hybrid larch F1 (2.18 and 4.36 ppm h AOT40), suggesting a higher O3 susceptibility of the hybrid. However, the use of PODY reconciled the species-specific differences, because the CLs were similar, that is, 9.40 and 12.00 mmol m–2 POD0 and 2.21 and 4.31 mmol m–2 POD1 in Japanese larch versus 10.44 and 12.38 mmol m–2 POD0 and 2.45 and 4.19 mmol m–2 POD1 in the hybrid, for 2% and 4% biomass loss, respectively. Overall, the CLs were lower than those in other forest species, which suggests a relatively high susceptibility of these larches. These results will inform environmental policy-makers and modelers about larch susceptibility to O3.

Research paper thumbnail of Interactive effect of leaf age and ozone on mesophyll conductance in Siebold's beech

Physiologia Plantarum

Mesophyll conductance (Gm ) is one of the most important factors determining photosynthesis. Trop... more Mesophyll conductance (Gm ) is one of the most important factors determining photosynthesis. Tropospheric ozone (O3 ) is known to accelerate leaf senescence and causes a decline of photosynthetic activity in leaves. However, the effects of age-related variation of O3 on Gm have not been well investigated, and we, therefore, analysed leaf gas exchange data in a free-air O3 exposure experiment on Siebold's beech with two levels (ambient and elevated O3 : 28 and 62 nmol mol-1 as daylight average, respectively). In addition, we examined whether O3 -induced changes on leaf morphology (leaf mass per area, leaf density and leaf thickness) may affect CO2 diffusion inside leaves. We found that O3 damaged the photosynthetic biochemistry progressively during the growing season. The Gm was associated with a reduced photosynthesis in O3 -fumigated Siebold's beech in August. The O3 -induced reduction of Gm was negatively correlated with leaf density, which was increased by elevated O3 , suggesting that the reduction of Gm was accompanied by changes in the physical structure of mesophyll cells. On the other hand, in October, the O3 -induced decrease of Gm was diminished because Gm decreased due to leaf senescence regardless of O3 treatment. The reduction of photosynthesis in senescent leaves after O3 exposure was mainly due to a decrease of maximum carboxylation rate (Vcmax ) and/or maximum electron transport rate (Jmax ) rather than diffusive limitations to CO2 transport such as Gm . A leaf age×O3 interaction of photosynthetic response will be a key for modelling photosynthesis in O3 -polluted environments. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Elevated ozone prevents acquisition of available nitrogen due to smaller root surface area in poplar

Research paper thumbnail of Vehicle-induced compaction of forest soil affects plant morphological and physiological attributes: A meta-analysis

Forest Ecology and Management

Abstract A main disadvantage of heavy machinery in forest operation is soil compaction. Compacted... more Abstract A main disadvantage of heavy machinery in forest operation is soil compaction. Compacted soils may be a barrier to seedling growth, even though the exact mechanisms of action are not clear yet, especially for different soil textures, plant species and ages. Previous meta-analyses did not find significant effects, mostly due to the limited size of their databases. We analyzed 45 articles for above-ground and below-ground morphological traits and 17 articles for physiological traits, and found significant declines following soil compaction. Declines were higher at below-ground than above-ground traits, in younger (

Research paper thumbnail of Flux-Based Ozone Risk Assessment for a Plant Injury Index (PII) in Three European Cool-Temperate Deciduous Tree Species

Forests

This study investigated visible foliar ozone (O3) injury in three deciduous tree species with dif... more This study investigated visible foliar ozone (O3) injury in three deciduous tree species with different growth patterns (indeterminate, Alnus glutinosa (L.) Gaertn.; intermediate, Sorbus aucuparia L.; and determinate, Vaccinium myrtillus L.) from May to August 2018. Ozone effects on the timing of injury onset and a plant injury index (PII) were investigated using two O3 indices, i.e., AOT40 (accumulative O3 exposure over 40 ppb during daylight hours) and PODY (phytotoxic O3 dose above a flux threshold of Y nmol m−2 s−1). A new parameterization for PODY estimation was developed for each species. Measurements were carried out in an O3 free-air controlled exposure (FACE) experiment with three levels of O3 treatment (ambient, AA; 1.5 × AA; and 2.0 × AA). Injury onset was found in May at 2.0 × AA in all three species and the timing of the onset was determined by the amount of stomatal O3 uptake. It required 4.0 mmol m−2 POD0 and 5.5 to 9.0 ppm·h AOT40. As a result, A. glutinosa with high...

Research paper thumbnail of Water use strategy affects avoidance of ozone stress by stomatal closure in Mediterranean trees –A modelling analysis

Plant, Cell & Environment

Research paper thumbnail of Ozone-induced impairment of night-time stomatal closure in O3-sensitive poplar clone is affected by nitrogen but not by phosphorus enrichment

Science of The Total Environment

Nocturnal transpiration may be a key factor influencing water use in plants. Tropospheric ozone (... more Nocturnal transpiration may be a key factor influencing water use in plants. Tropospheric ozone (O3) and availability of nutrients such as nitrogen (N) and phosphorus (P) in the soil can affect daytime water use through stomata, but the combined effects of O3, N and P on night-time stomatal conductance (gs) are not known. We investigated the effects of O3 and soil availability of N and P on nocturnal gs and the dynamics of stomatal response after leaf severing in an O3-sensitive poplar clone (Oxford) subjected to combined treatments over a growing season in an O3 free air controlled exposure (FACE) facility. The treatments were two soil N levels (0 and 80 kg N ha-1; N0 and N80), three soil P levels (0, 40 and 80 kg P ha-1; P0, P40 and P80) and three O3 levels (ambient concentration, AA [35.0 ppb as hourly mean]; 1.5 × AA; 2.0 × AA). The analysis of stomatal dynamics after leaf severing suggested that O3 impaired stomatal closure execution. As a result, nocturnal gs was increased by 2.0 × AA O3 in August (+39%) and September (+108%). Night-time gs was correlated with POD0 (phytotoxic O3 dose) and increased exponentially after 40 mmol m-2 POD0. Such increase of nocturnal gs was attributed to the emission of ethylene due to 2.0 × AA O3 exposure, while foliar abscisic acid (ABA) or indole-3-acetic acid (IAA) did not affect gs at night. Interestingly, the O3-induced stomatal opening at night was limited by N treatments in August, but not limited in September. Phosphorus decreased nocturnal gs, although P did not modify the O3-induced stomatal dysfunction. The results suggest that the increased nocturnal gs may be associated with a need to improve N acquisition to cope with O3 stress.

Research paper thumbnail of Effect of Long-Term vs. Short-Term Ambient Ozone Exposure on Radial Stem Growth, Sap Flux and Xylem Morphology of O3-Sensitive Poplar Trees

Forests

High ozone (O3) pollution impairs the carbon and water balance of trees, which is of special inte... more High ozone (O3) pollution impairs the carbon and water balance of trees, which is of special interest in planted forests. However, the effect of long-term O3 exposure on tree growth and water use, little remains known. In this study, we analysed the relationships of intra-annual stem growth pattern, seasonal sap flow dynamics and xylem morphology to assess the effect of long term O3 exposure of mature O3-sensitive hybrid poplars (‘Oxford’ clone). Rooted cuttings were planted in autumn 2007 and drip irrigated with 2 liters of water as ambient O3 treatment, or 450 ppm ethylenediurea (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N0-phenylurea, abbreviated as EDU) solution as O3 protection treatment over all growing seasons. During 2013, point dendrometers and heat pulses were installed to monitor radial growth, stem water relations and sap flow. Ambient O3 did not affect growth rates, even if the seasonal culmination point was 20 days earlier on average than that recorded in the O3 protected tr...

Research paper thumbnail of Isoprene is more affected by climate drivers than monoterpenes: a meta-analytic review on plant isoprenoid emissions

Plant, Cell & Environment

Isoprene and monoterpenes (MTs) are among the most abundant and reactive volatile organic compoun... more Isoprene and monoterpenes (MTs) are among the most abundant and reactive volatile organic compounds produced by plants (biogenic volatile organic compounds). We conducted a meta-analysis to quantify the mean effect of environmental factors associated to climate change (warming, drought, elevated CO2 , and O3 ) on the emission of isoprene and MTs. Results indicated that all single factors except warming inhibited isoprene emission. When subsets of data collected in experiments run under similar change of a given environmental factor were compared, isoprene and photosynthesis responded negatively to elevated O3 (-8% and -10%, respectively) and drought (-15% and -42%), and in opposite ways to elevated CO2 (-23% and +55%) and warming (+53% and -23%, respectively). Effects on MTs emission were usually not significant, with the exceptions of a significant stimulation caused by warming (+39%) and by elevated O3 (limited to O3 -insensitive plants, and evergreen species with storage organs). Our results clearly highlight individual effects of environmental factors on isoprene and MT emissions, and an overall uncoupling between these secondary metabolites produced by the same methylerythritol 4-phosphate pathway. Future results from manipulative experiments and long-term observations may help untangling the interactive effects of these factors and filling gaps featured in the current meta-analysis.

Research paper thumbnail of Different belowground responses to elevated ozone and soil water deficit in three European oak species (Quercus ilex, Q. pubescens and Q. robur)

Science of The Total Environment

Effects on roots due to ozone and/or soil water deficit often occur through diminished belowgroun... more Effects on roots due to ozone and/or soil water deficit often occur through diminished belowground allocation of carbon. Responses of root biomass, morphology, anatomy and ectomycorrhizal communities were investigated in seedlings of three oak species: Quercus ilex L., Q. pubescens Willd. and Q. robur L., exposed to combined effects of elevated ozone (ambient air and 1.4 × ambient air) and water deficit (100% and 10% irrigation relative to field capacity) for one growing season at a free-air ozone exposure facility. Effects on root biomass were observed as general reduction in coarse root biomass by -26.8% and in fine root biomass by -13.1% due to water deficit. Effect on coarse root biomass was the most prominent in Q. robur (-36.3%). Root morphological changes manifested as changes in proportions of fine root (<2 mm) diameter classes due to ozone and water deficit in Q. pubescens and due to water deficit in Q. robur. In addition, reduced fine root diameter (-8.49%) in Q. robur was observed under water deficit. Changes in root anatomy were observed as increased vessel density (+18.5%) due to ozone in all three species, as reduced vessel tangential diameter (-46.7%) in Q. ilex due to interaction of ozone and water, and as generally increased bark to secondary xylem ratio (+47.0%) due to interaction of ozone and water. Water deficit influenced occurrence of distinct growth ring boundaries in roots of Q. ilex and Q. robur. It shifted the ectomycorrhizal community towards dominance of stress-resistant species, with reduced relative abundance of Tomentella sp. 2 and increased relative abundances of Sphaerosporella brunnea and Thelephora sp. Our results provide evidence that expression of stress effects varies between root traits; therefore the combined analysis of root traits is necessary to obtain a complete picture of belowground responses.

Research paper thumbnail of Should we see urban trees as effective solutions to reduce increasing ozone levels in cities?

Environmental pollution (Barking, Essex : 1987), 2018

Outdoor air pollution is considered as the most serious environmental problem for human health, a... more Outdoor air pollution is considered as the most serious environmental problem for human health, associated with some million deaths worldwide per year. Cities have to cope with the challenges due to poor air quality impacting human health and citizen well-being. According to an analysis in the framework of this study, the annual mean concentrations of tropospheric ozone (O) have been increasing by on average 0.16 ppb year in cities across the globe over the time period 1995-2014. Green urban infrastructure can improve air quality by removing O. To efficiently reduce O in cities, it is important to define suitable urban forest management, including proper species selection, with focus on the removal ability of O and other air pollutants, biogenic emission rates, allergenic effects and maintenance requirements. This study reanalyzes the literature to i) quantify O removal by urban vegetation categorized into trees/shrubs and green roofs; ii) rank 95 urban plant species based on the ab...

Research paper thumbnail of Can nutrient fertilization mitigate the effects of ozone exposure on an ozone-sensitive poplar clone?

Science of The Total Environment

We tested the independent and interactive effects of nitrogen (N; 0 and 80 kg ha), phosphorus (P;... more We tested the independent and interactive effects of nitrogen (N; 0 and 80 kg ha), phosphorus (P; 0, 40 and 80 kg ha), and ozone (O) application/exposure [ambient concentration (AA), 1.5 × AA and 2.0 × AA] for five consecutive months on biochemical traits of the O-sensitive Oxford poplar clone. Plants exposed to O showed visible injury and an alteration of membrane integrity, as confirmed by the malondialdehyde by-product accumulation (+3 and +17% under 1.5 × AA and 2.0 × AA conditions, in comparison to AA). This was probably due to O-induced oxidative damage, as documented by the production of superoxide anion radical (O, +27 and +63%, respectively). Ozone per se, independently from the concentrations, induced multiple signals (e.g., alteration of cellular redox state, increase of abscisic acid/indole-3-acetic acid ratio and reduction of proline content) that might be part of premature leaf senescence processes. By contrast, nutrient fertilization (both N and P) reduced reactive oxygen species accumulation (as confirmed by the decreased O and hydrogen peroxide content), resulting in enhanced membrane stability. This was probably due to the simultaneous involvement of antioxidant compounds (e.g., carotenoids, ascorbate and glutathione) and osmoprotectants (e.g., proline) that regulate the detoxification processes of coping with oxidative stress by reducing the O sensitivity of Oxford clone. These mitigation effects were effective only under AA and 1.5 × AA conditions. Nitrogen and P supply activated a free radical scavenging system that was not able to delay leaf senescence and mitigate the adverse effects of a general peroxidation due to the highest O concentrations.

Research paper thumbnail of Cross-talk between physiological and biochemical adjustments by Punica granatum cv. Dente di cavallo mitigates the effects of salinity and ozone stress

Science of The Total Environment

No evidence of visible injury due to salt (e.g. tip yellow-brown necrosis) was found. • Physiolog... more No evidence of visible injury due to salt (e.g. tip yellow-brown necrosis) was found. • Physiological and biochemical adjustments were induced by salt and/or O 3 exposure. • In the combined treatment, salt did not ameliorate the negative effects of O 3 .

Research paper thumbnail of Effects of nitrogen and phosphorus imbalance on photosynthetic traits of poplar Oxford clone under ozone pollution

Journal of Plant Research

Ozone (O) pollution and the availability of nitrogen (N) and phosphorus (P) in the soil both affe... more Ozone (O) pollution and the availability of nitrogen (N) and phosphorus (P) in the soil both affect plant photosynthesis and chlorophyll (Chl) content, but the interaction of O and nutrition is unclear. We postulated that the nutritional condition changes plant photosynthetic responses to O. An O-sensitive poplar clone (Oxford) was subject to two N levels (N0, 0 kg N ha; N80, 80 kg N ha), two P levels (P0, 0 kg P ha; P80, 80 kg P ha) and three levels of O exposure (ambient concentration, AA; 1.5 × AA; 2.0 × AA) over a growing season in an O free air controlled exposure (FACE) facility. The daily change of leaf gas exchange and dark respiration (R) were investigated at mid-summer (August). Chl a fluorescence was measured three times in July, August and September. At the end of the growing season, Chl content was measured. It was found that Chl content, the maximum quantum yield (F/F), Chl a fluorescence performance index (PI) and gas exchange were negatively affected by elevated O. Phosphorus may mitigate the O-induced reduction of the ratio of photosynthesis to stomatal conductance, while it exacerbated the O-induced loss of F/F. Nitrogen alleviated negative effects of O on F/F and PI in July. Ozone-induced loss of net photosynthetic rate was mitigated by N in medium O exposure (1.5 × AA). However, such a mitigation effect was not observed in the higher O level (2.0 × AA). Nitrogen addition exacerbated O-induced increase of R suggesting an increased respiratory carbon loss in the presence of O and N. This may result in a further reduction of the net carbon gain for poplars exposed to O.

Research paper thumbnail of Photosynthetic activity in relation to a gradient of leaf nitrogen content within a canopy of Siebold's beech and Japanese oak saplings under elevated ozone

The Science of the total environment, Jan 15, 2018

The primary objective of this study was to describe parameters related to the leaf biochemical as... more The primary objective of this study was to describe parameters related to the leaf biochemical assimilation capacity of photosynthesis, such as the maximum rates of carboxylation (V) and electron transport (J), as a function of the leaf nitrogen content throughout a canopy of Siebold's beech and Japanese oak grown under elevated ozone (O) conditions during a growing season. To this end, we investigated the relationship between photosynthetic traits and leaf nitrogen content in various canopy positions of two tree species under free-air O exposure (60 nmol mol, during daylight hours) in June, August, and October 2012. We observed O-induced reduction in V and J without reduction of leaf nitrogen content in both tree species. In Siebold's beech, V and J in leaves with higher N were largely decreased by O from August, while little effect of O was observed in leaves with lower N. On the other hand, there was no difference in the extent of O-induced reduction in V and J across the...

Research paper thumbnail of Stress markers and physiochemical responses of the Mediterranean shrub Phillyrea angustifolia under current and future drought and ozone scenarios

Research paper thumbnail of Exposure- and flux-based assessment of ozone risk to sugarcane plants

Research paper thumbnail of Ozone impairs the response of isoprene emission to foliar nitrogen and phosphorus in poplar

Research paper thumbnail of Hyperspectral Reflectance of Light-Adapted Leaves Can Predict Both Dark- and Light-Adapted Chl Fluorescence Parameters, and the Effects of Chronic Ozone Exposure on Date Palm (Phoenix dactylifera)

International Journal of Molecular Sciences

High-throughput and large-scale measurements of chlorophyll a fluorescence (ChlF) are of great in... more High-throughput and large-scale measurements of chlorophyll a fluorescence (ChlF) are of great interest to investigate the photosynthetic performance of plants in the field. Here, we tested the capability to rapidly, precisely, and simultaneously estimate the number of pulse-amplitude-modulation ChlF parameters commonly calculated from both dark- and light-adapted leaves (an operation which usually takes tens of minutes) from the reflectance of hyperspectral data collected on light-adapted leaves of date palm seedlings chronically exposed in a FACE facility to three ozone (O3) concentrations (ambient air, AA; target 1.5 × AA O3, named as moderate O3, MO; target 2 × AA O3, named as elevated O3, EO) for 75 consecutive days. Leaf spectral measurements were paired with reference measurements of ChlF, and predictive spectral models were constructed using partial least squares regression. Most of the ChlF parameters were well predicted by spectroscopic models (average model goodness-of-fi...

Research paper thumbnail of Isotopic and Water Relation Responses to Ozone and Water Stress in Seedlings of Three Oak Species with Different Adaptation Strategies

Forests

The impact of global changes on forest ecosystem processes is based on the species-specific respo... more The impact of global changes on forest ecosystem processes is based on the species-specific responses of trees to the combined effect of multiple stressors and the capacity of each species to acclimate and cope with the environment modification. Combined environmental constraints can severely affect plant and ecological processes involved in plant functionality. This study provides novel insights into the impact of a simultaneous pairing of abiotic stresses (i.e., water and ozone (O3) stress) on the responses of oak species. Water stress (using 40 and 100% of soil water content at field capacity—WS and WW treatments, respectively) and O3 exposure (1.0, 1.2, and 1.4 times the ambient concentration—AA, 1.2AA, and 1.4AA, respectively) were carried out on Quercus robur L., Quercus ilex L., and Quercus pubescens Willd. seedlings, to study physiological traits (1. isotope signature [δ13C, δ18O and δ15N], 2. water relation [leaf water potential, leaf water content], 3. leaf gas exchange [l...

Research paper thumbnail of Developing Ozone Risk Assessment for Larch Species

Frontiers in Forests and Global Change

Ozone (O3) risk assessment for the protection of forests requires species-specific critical level... more Ozone (O3) risk assessment for the protection of forests requires species-specific critical levels (CLs), based on either O3 concentrations (AOT40) or stomatal uptake (PODY) accumulation over the growing season. Larch (Larix sp.) is a genus with O3-susceptible species, widely distributed in the northern hemisphere and with global economic importance. We analyzed published and unpublished data of Japanese larch (Larix kaempferi) and its hybrid F1 (Larix gmelinii var. japonica × L. kaempferi) stomatal responses for developing a parameterization of stomatal conductance model and estimating PODY-based CLs with two Y thresholds, that is, 0 and 1 nmol m–2 s–1 projected leaf area (PLA). In parallel, we estimated AOT40-based CLs. The results show that the AOT40-based CLs for a 2% and 4% biomass loss in Japanese larch were 5.79 and 11.59 ppm h, that is, higher than those in hybrid larch F1 (2.18 and 4.36 ppm h AOT40), suggesting a higher O3 susceptibility of the hybrid. However, the use of PODY reconciled the species-specific differences, because the CLs were similar, that is, 9.40 and 12.00 mmol m–2 POD0 and 2.21 and 4.31 mmol m–2 POD1 in Japanese larch versus 10.44 and 12.38 mmol m–2 POD0 and 2.45 and 4.19 mmol m–2 POD1 in the hybrid, for 2% and 4% biomass loss, respectively. Overall, the CLs were lower than those in other forest species, which suggests a relatively high susceptibility of these larches. These results will inform environmental policy-makers and modelers about larch susceptibility to O3.

Research paper thumbnail of Interactive effect of leaf age and ozone on mesophyll conductance in Siebold's beech

Physiologia Plantarum

Mesophyll conductance (Gm ) is one of the most important factors determining photosynthesis. Trop... more Mesophyll conductance (Gm ) is one of the most important factors determining photosynthesis. Tropospheric ozone (O3 ) is known to accelerate leaf senescence and causes a decline of photosynthetic activity in leaves. However, the effects of age-related variation of O3 on Gm have not been well investigated, and we, therefore, analysed leaf gas exchange data in a free-air O3 exposure experiment on Siebold's beech with two levels (ambient and elevated O3 : 28 and 62 nmol mol-1 as daylight average, respectively). In addition, we examined whether O3 -induced changes on leaf morphology (leaf mass per area, leaf density and leaf thickness) may affect CO2 diffusion inside leaves. We found that O3 damaged the photosynthetic biochemistry progressively during the growing season. The Gm was associated with a reduced photosynthesis in O3 -fumigated Siebold's beech in August. The O3 -induced reduction of Gm was negatively correlated with leaf density, which was increased by elevated O3 , suggesting that the reduction of Gm was accompanied by changes in the physical structure of mesophyll cells. On the other hand, in October, the O3 -induced decrease of Gm was diminished because Gm decreased due to leaf senescence regardless of O3 treatment. The reduction of photosynthesis in senescent leaves after O3 exposure was mainly due to a decrease of maximum carboxylation rate (Vcmax ) and/or maximum electron transport rate (Jmax ) rather than diffusive limitations to CO2 transport such as Gm . A leaf age×O3 interaction of photosynthetic response will be a key for modelling photosynthesis in O3 -polluted environments. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Elevated ozone prevents acquisition of available nitrogen due to smaller root surface area in poplar

Research paper thumbnail of Vehicle-induced compaction of forest soil affects plant morphological and physiological attributes: A meta-analysis

Forest Ecology and Management

Abstract A main disadvantage of heavy machinery in forest operation is soil compaction. Compacted... more Abstract A main disadvantage of heavy machinery in forest operation is soil compaction. Compacted soils may be a barrier to seedling growth, even though the exact mechanisms of action are not clear yet, especially for different soil textures, plant species and ages. Previous meta-analyses did not find significant effects, mostly due to the limited size of their databases. We analyzed 45 articles for above-ground and below-ground morphological traits and 17 articles for physiological traits, and found significant declines following soil compaction. Declines were higher at below-ground than above-ground traits, in younger (

Research paper thumbnail of Flux-Based Ozone Risk Assessment for a Plant Injury Index (PII) in Three European Cool-Temperate Deciduous Tree Species

Forests

This study investigated visible foliar ozone (O3) injury in three deciduous tree species with dif... more This study investigated visible foliar ozone (O3) injury in three deciduous tree species with different growth patterns (indeterminate, Alnus glutinosa (L.) Gaertn.; intermediate, Sorbus aucuparia L.; and determinate, Vaccinium myrtillus L.) from May to August 2018. Ozone effects on the timing of injury onset and a plant injury index (PII) were investigated using two O3 indices, i.e., AOT40 (accumulative O3 exposure over 40 ppb during daylight hours) and PODY (phytotoxic O3 dose above a flux threshold of Y nmol m−2 s−1). A new parameterization for PODY estimation was developed for each species. Measurements were carried out in an O3 free-air controlled exposure (FACE) experiment with three levels of O3 treatment (ambient, AA; 1.5 × AA; and 2.0 × AA). Injury onset was found in May at 2.0 × AA in all three species and the timing of the onset was determined by the amount of stomatal O3 uptake. It required 4.0 mmol m−2 POD0 and 5.5 to 9.0 ppm·h AOT40. As a result, A. glutinosa with high...

Research paper thumbnail of Water use strategy affects avoidance of ozone stress by stomatal closure in Mediterranean trees –A modelling analysis

Plant, Cell & Environment

Research paper thumbnail of Ozone-induced impairment of night-time stomatal closure in O3-sensitive poplar clone is affected by nitrogen but not by phosphorus enrichment

Science of The Total Environment

Nocturnal transpiration may be a key factor influencing water use in plants. Tropospheric ozone (... more Nocturnal transpiration may be a key factor influencing water use in plants. Tropospheric ozone (O3) and availability of nutrients such as nitrogen (N) and phosphorus (P) in the soil can affect daytime water use through stomata, but the combined effects of O3, N and P on night-time stomatal conductance (gs) are not known. We investigated the effects of O3 and soil availability of N and P on nocturnal gs and the dynamics of stomatal response after leaf severing in an O3-sensitive poplar clone (Oxford) subjected to combined treatments over a growing season in an O3 free air controlled exposure (FACE) facility. The treatments were two soil N levels (0 and 80 kg N ha-1; N0 and N80), three soil P levels (0, 40 and 80 kg P ha-1; P0, P40 and P80) and three O3 levels (ambient concentration, AA [35.0 ppb as hourly mean]; 1.5 × AA; 2.0 × AA). The analysis of stomatal dynamics after leaf severing suggested that O3 impaired stomatal closure execution. As a result, nocturnal gs was increased by 2.0 × AA O3 in August (+39%) and September (+108%). Night-time gs was correlated with POD0 (phytotoxic O3 dose) and increased exponentially after 40 mmol m-2 POD0. Such increase of nocturnal gs was attributed to the emission of ethylene due to 2.0 × AA O3 exposure, while foliar abscisic acid (ABA) or indole-3-acetic acid (IAA) did not affect gs at night. Interestingly, the O3-induced stomatal opening at night was limited by N treatments in August, but not limited in September. Phosphorus decreased nocturnal gs, although P did not modify the O3-induced stomatal dysfunction. The results suggest that the increased nocturnal gs may be associated with a need to improve N acquisition to cope with O3 stress.

Research paper thumbnail of Effect of Long-Term vs. Short-Term Ambient Ozone Exposure on Radial Stem Growth, Sap Flux and Xylem Morphology of O3-Sensitive Poplar Trees

Forests

High ozone (O3) pollution impairs the carbon and water balance of trees, which is of special inte... more High ozone (O3) pollution impairs the carbon and water balance of trees, which is of special interest in planted forests. However, the effect of long-term O3 exposure on tree growth and water use, little remains known. In this study, we analysed the relationships of intra-annual stem growth pattern, seasonal sap flow dynamics and xylem morphology to assess the effect of long term O3 exposure of mature O3-sensitive hybrid poplars (‘Oxford’ clone). Rooted cuttings were planted in autumn 2007 and drip irrigated with 2 liters of water as ambient O3 treatment, or 450 ppm ethylenediurea (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N0-phenylurea, abbreviated as EDU) solution as O3 protection treatment over all growing seasons. During 2013, point dendrometers and heat pulses were installed to monitor radial growth, stem water relations and sap flow. Ambient O3 did not affect growth rates, even if the seasonal culmination point was 20 days earlier on average than that recorded in the O3 protected tr...

Research paper thumbnail of Isoprene is more affected by climate drivers than monoterpenes: a meta-analytic review on plant isoprenoid emissions

Plant, Cell & Environment

Isoprene and monoterpenes (MTs) are among the most abundant and reactive volatile organic compoun... more Isoprene and monoterpenes (MTs) are among the most abundant and reactive volatile organic compounds produced by plants (biogenic volatile organic compounds). We conducted a meta-analysis to quantify the mean effect of environmental factors associated to climate change (warming, drought, elevated CO2 , and O3 ) on the emission of isoprene and MTs. Results indicated that all single factors except warming inhibited isoprene emission. When subsets of data collected in experiments run under similar change of a given environmental factor were compared, isoprene and photosynthesis responded negatively to elevated O3 (-8% and -10%, respectively) and drought (-15% and -42%), and in opposite ways to elevated CO2 (-23% and +55%) and warming (+53% and -23%, respectively). Effects on MTs emission were usually not significant, with the exceptions of a significant stimulation caused by warming (+39%) and by elevated O3 (limited to O3 -insensitive plants, and evergreen species with storage organs). Our results clearly highlight individual effects of environmental factors on isoprene and MT emissions, and an overall uncoupling between these secondary metabolites produced by the same methylerythritol 4-phosphate pathway. Future results from manipulative experiments and long-term observations may help untangling the interactive effects of these factors and filling gaps featured in the current meta-analysis.

Research paper thumbnail of Different belowground responses to elevated ozone and soil water deficit in three European oak species (Quercus ilex, Q. pubescens and Q. robur)

Science of The Total Environment

Effects on roots due to ozone and/or soil water deficit often occur through diminished belowgroun... more Effects on roots due to ozone and/or soil water deficit often occur through diminished belowground allocation of carbon. Responses of root biomass, morphology, anatomy and ectomycorrhizal communities were investigated in seedlings of three oak species: Quercus ilex L., Q. pubescens Willd. and Q. robur L., exposed to combined effects of elevated ozone (ambient air and 1.4 × ambient air) and water deficit (100% and 10% irrigation relative to field capacity) for one growing season at a free-air ozone exposure facility. Effects on root biomass were observed as general reduction in coarse root biomass by -26.8% and in fine root biomass by -13.1% due to water deficit. Effect on coarse root biomass was the most prominent in Q. robur (-36.3%). Root morphological changes manifested as changes in proportions of fine root (<2 mm) diameter classes due to ozone and water deficit in Q. pubescens and due to water deficit in Q. robur. In addition, reduced fine root diameter (-8.49%) in Q. robur was observed under water deficit. Changes in root anatomy were observed as increased vessel density (+18.5%) due to ozone in all three species, as reduced vessel tangential diameter (-46.7%) in Q. ilex due to interaction of ozone and water, and as generally increased bark to secondary xylem ratio (+47.0%) due to interaction of ozone and water. Water deficit influenced occurrence of distinct growth ring boundaries in roots of Q. ilex and Q. robur. It shifted the ectomycorrhizal community towards dominance of stress-resistant species, with reduced relative abundance of Tomentella sp. 2 and increased relative abundances of Sphaerosporella brunnea and Thelephora sp. Our results provide evidence that expression of stress effects varies between root traits; therefore the combined analysis of root traits is necessary to obtain a complete picture of belowground responses.

Research paper thumbnail of Should we see urban trees as effective solutions to reduce increasing ozone levels in cities?

Environmental pollution (Barking, Essex : 1987), 2018

Outdoor air pollution is considered as the most serious environmental problem for human health, a... more Outdoor air pollution is considered as the most serious environmental problem for human health, associated with some million deaths worldwide per year. Cities have to cope with the challenges due to poor air quality impacting human health and citizen well-being. According to an analysis in the framework of this study, the annual mean concentrations of tropospheric ozone (O) have been increasing by on average 0.16 ppb year in cities across the globe over the time period 1995-2014. Green urban infrastructure can improve air quality by removing O. To efficiently reduce O in cities, it is important to define suitable urban forest management, including proper species selection, with focus on the removal ability of O and other air pollutants, biogenic emission rates, allergenic effects and maintenance requirements. This study reanalyzes the literature to i) quantify O removal by urban vegetation categorized into trees/shrubs and green roofs; ii) rank 95 urban plant species based on the ab...

Research paper thumbnail of Can nutrient fertilization mitigate the effects of ozone exposure on an ozone-sensitive poplar clone?

Science of The Total Environment

We tested the independent and interactive effects of nitrogen (N; 0 and 80 kg ha), phosphorus (P;... more We tested the independent and interactive effects of nitrogen (N; 0 and 80 kg ha), phosphorus (P; 0, 40 and 80 kg ha), and ozone (O) application/exposure [ambient concentration (AA), 1.5 × AA and 2.0 × AA] for five consecutive months on biochemical traits of the O-sensitive Oxford poplar clone. Plants exposed to O showed visible injury and an alteration of membrane integrity, as confirmed by the malondialdehyde by-product accumulation (+3 and +17% under 1.5 × AA and 2.0 × AA conditions, in comparison to AA). This was probably due to O-induced oxidative damage, as documented by the production of superoxide anion radical (O, +27 and +63%, respectively). Ozone per se, independently from the concentrations, induced multiple signals (e.g., alteration of cellular redox state, increase of abscisic acid/indole-3-acetic acid ratio and reduction of proline content) that might be part of premature leaf senescence processes. By contrast, nutrient fertilization (both N and P) reduced reactive oxygen species accumulation (as confirmed by the decreased O and hydrogen peroxide content), resulting in enhanced membrane stability. This was probably due to the simultaneous involvement of antioxidant compounds (e.g., carotenoids, ascorbate and glutathione) and osmoprotectants (e.g., proline) that regulate the detoxification processes of coping with oxidative stress by reducing the O sensitivity of Oxford clone. These mitigation effects were effective only under AA and 1.5 × AA conditions. Nitrogen and P supply activated a free radical scavenging system that was not able to delay leaf senescence and mitigate the adverse effects of a general peroxidation due to the highest O concentrations.

Research paper thumbnail of Cross-talk between physiological and biochemical adjustments by Punica granatum cv. Dente di cavallo mitigates the effects of salinity and ozone stress

Science of The Total Environment

No evidence of visible injury due to salt (e.g. tip yellow-brown necrosis) was found. • Physiolog... more No evidence of visible injury due to salt (e.g. tip yellow-brown necrosis) was found. • Physiological and biochemical adjustments were induced by salt and/or O 3 exposure. • In the combined treatment, salt did not ameliorate the negative effects of O 3 .

Research paper thumbnail of Effects of nitrogen and phosphorus imbalance on photosynthetic traits of poplar Oxford clone under ozone pollution

Journal of Plant Research

Ozone (O) pollution and the availability of nitrogen (N) and phosphorus (P) in the soil both affe... more Ozone (O) pollution and the availability of nitrogen (N) and phosphorus (P) in the soil both affect plant photosynthesis and chlorophyll (Chl) content, but the interaction of O and nutrition is unclear. We postulated that the nutritional condition changes plant photosynthetic responses to O. An O-sensitive poplar clone (Oxford) was subject to two N levels (N0, 0 kg N ha; N80, 80 kg N ha), two P levels (P0, 0 kg P ha; P80, 80 kg P ha) and three levels of O exposure (ambient concentration, AA; 1.5 × AA; 2.0 × AA) over a growing season in an O free air controlled exposure (FACE) facility. The daily change of leaf gas exchange and dark respiration (R) were investigated at mid-summer (August). Chl a fluorescence was measured three times in July, August and September. At the end of the growing season, Chl content was measured. It was found that Chl content, the maximum quantum yield (F/F), Chl a fluorescence performance index (PI) and gas exchange were negatively affected by elevated O. Phosphorus may mitigate the O-induced reduction of the ratio of photosynthesis to stomatal conductance, while it exacerbated the O-induced loss of F/F. Nitrogen alleviated negative effects of O on F/F and PI in July. Ozone-induced loss of net photosynthetic rate was mitigated by N in medium O exposure (1.5 × AA). However, such a mitigation effect was not observed in the higher O level (2.0 × AA). Nitrogen addition exacerbated O-induced increase of R suggesting an increased respiratory carbon loss in the presence of O and N. This may result in a further reduction of the net carbon gain for poplars exposed to O.

Research paper thumbnail of Photosynthetic activity in relation to a gradient of leaf nitrogen content within a canopy of Siebold's beech and Japanese oak saplings under elevated ozone

The Science of the total environment, Jan 15, 2018

The primary objective of this study was to describe parameters related to the leaf biochemical as... more The primary objective of this study was to describe parameters related to the leaf biochemical assimilation capacity of photosynthesis, such as the maximum rates of carboxylation (V) and electron transport (J), as a function of the leaf nitrogen content throughout a canopy of Siebold's beech and Japanese oak grown under elevated ozone (O) conditions during a growing season. To this end, we investigated the relationship between photosynthetic traits and leaf nitrogen content in various canopy positions of two tree species under free-air O exposure (60 nmol mol, during daylight hours) in June, August, and October 2012. We observed O-induced reduction in V and J without reduction of leaf nitrogen content in both tree species. In Siebold's beech, V and J in leaves with higher N were largely decreased by O from August, while little effect of O was observed in leaves with lower N. On the other hand, there was no difference in the extent of O-induced reduction in V and J across the...