Intra-annual Pattern of Photosynthesis, Growth and Stable Isotope Partitioning in a Poplar Clone Subjected to Ozone and Water Stress (original) (raw)
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Trees, 2010
An open-top chamber experiment was carried out in Curno (Northern Italy) in 2004 and 2005 on seedlings of Fagus sylvatica (FS), Quercus robur (QR), and an ozone-sensitive Populus (POP) clone, to investigate the role of two stress factors: tropospheric ozone and water shortage. Treatments were filtered air to achieve a 50% reduction in the environmental ozone concentrations (charcoal filtered, CF); and non-filtered air, with a 5% reduction in the environmental ozone concentrations (non-filtered, NF). Overall ozone exposure (AOT40) in open air (April-September) was 26,995 ppb h in 2004 and 25,166 ppb h in 2005. The plants were either watered (W)
Severe drought events increase the sensitivity to ozone on poplar clones
An open-top chamber experiment has been carried out at the facilities of Curno (North Italy), in June-August 2009, to assess the response to ozone in two poplar clones Populus maximowiczii Henry × P. berolinensis Dippel (Oxford clone, OX), and Populus nigra "Jean Pourtet" (JP) in concomitance of severe drought events. Three different water regimes were applied: W -Well Watered Control: field capacity; D1 -Drought Treatment 1: field capacity until begin July, then reduced water availability (plants were then subjected to severe drought events); D2 -Drought Treatment 2: constant water shortage (plants were then subjected to severe drought events). Leaf water potential, gas exchange and chlorophyll fluorescence (JIP-test) were assessed every 2 weeks; growth parameters and stable isotope composition (ı 13 C and ı 18 O) were measured at the end of the experiment. The main results were: (i) drought, but not ozone, reduced photosynthesis and growth and increased ı 13 C; (ii) the two clones showed different strategies to cope with ozone stress: JP shed the damaged leaves, whereas OX maintained their leaves ozone provoked the loss of leaves in W plants of the JP clone; (iii) in the D1 plants the response to drought provokes an additional effects with the effect of ozone absorbed before the severe drought events; (iv) D2 plants did not respond to ozone until the last event, when a clear synergistic effect between the two stressors was observed. We conclude that ozone had different effects in relation to the way the drought stress was applied. These results are discussed for their ecological consequence on vegetation in field conditions.
The Science of the total environment, 2017
Poplar clones 546 (P. deltoides cv. '55/56'×P. deltoides cv. 'Imperial') and 107 (P. euramericana cv. '74/76') were exposed to five ozone concentrations in 15 open-top chambers (OTCs). Both ozone exposure (AOT40, Accumulation Over a Threshold hourly ozone concentration of 40ppb) and flux-based (POD7, Phytotoxic Ozone Dose above an hourly flux threshold of 7nmol O3 m(-2) PLA (projected leaf area) s(-1)) response relationships were established with photosynthesis, leaf morphology and biomass variables. Increases in both metrics showed significant negative relationships with light-saturated photosynthesis rate, chlorophyll content, leaf mass per area, actual photochemical efficiency of PSII in the light and root biomass but not with stomatal conductance (gs), leaf and stem biomass. Ozone had a greater impact on belowground than on aboveground biomass. The ranking of these indicators from higher to lower sensitivity to ozone was: photosynthetic parameters, morpho...
Environmental Pollution, 1994
During two consecutive growing seasons, the same potted individuals of European aspen (Populus tremula), grown from root cuttings of one clone, were fumigated with either ambient air or ozone concentrations of 0 (control), 0.05 or O,I $itre litrel. Structure and biomass of the annually formed branches were analysed after excision at the end of each season. Only at 0.1 plitre lit& was branch weight reduced, and crooked axes occurred in each season. During the second season, branch length and leaf sizes were strongly reduced, while many leaves displayed yellowish deficiency symptoms and lowered cation concentrations. Such leaves contrasted to those showing characteristic O,-bronzing. Although foliage density was enhanced due to reduced branch length, the area of attached foliage was limited by the small leaf sizes, necrotic leaves and premature leaf loss. During midsummer of the second fumigation period, photosynthetic capacity, carboxylation ejiciency and water-use eficiency (WUE) declined in (attached) yellowish and bronze leaves at 0.1 ditre litrel, whereas green leaves at 0.05 plitre litre' displayed accelerated senescence in late summer while maintaining WUE. It is concluded that the d@erences in branch growth between the two growing seasons were caused in part by internal changes in those plant organs (root and basal stem), which had experienced both fumigation periods.
Physiologia Plantarum, 2008
Young poplar trees (Populus tremula Michx. Â Populus alba L. clone INRA 717-1B4) were subjected to 120 ppb of ozone for 35 days in phytotronic chambers. Treated trees displayed precocious leaf senescence and visible symptoms of injury (dark brown/black upper surface stippling) exclusively observed on fully expanded leaves. In these leaves, ozone reduced parameters related to photochemistry (Chl content and maximum rate of photosynthetic electron transport) and photosynthetic CO 2 fixation [net CO 2 assimilation, Rubisco (ribulose-1,5-bisphosphate carboxylase oxygenase) activity and maximum velocity of Rubisco for carboxylation]. In fully expanded leaves, the rate of photorespiration as estimated from Chl fluorescence was markedly impaired by the ozone treatment together with the activity of photorespiratory enzymes (Rubisco and glycolate oxidase). Immunoblot analysis revealed a decrease in the content of serine hydroxymethyltransferase in treated mature leaves, while the content of the H subunit of the glycine decarboxylase complex was not modified. Leaves in the early period of expansion were exempt from visible symptoms of injury and remained unaffected as regards all measured parameters. Leaves reaching full expansion under ozone exposure showed potential responses of protection (stimulation of mitochondrial respiration and transitory stomatal closure). Our data underline the major role of leaf phenology in ozone sensitivity of photosynthetic processes and reveal a marked ozone-induced inhibition of photorespiration.
Differential impact of chronic ozone exposure on expanding and fully expanded poplar leaves
Tree Physiology, 2010
Populus tremula L. × Populus alba L. (Populus×canescens (Aiton) Smith)clone INRA 717-1-B4 saplings (50 cm apex to base and carrying 19 leaves on average)were followed for 28 days. Half of the trees were grown in charcoal-filtered air while the other half were exposed to 120 ppb ozone for 11 h a day during the light period. The expanding leaf number 4 was tagged at the beginning of the experiment and finished expansion between 7 and 14 days. These leaves were harvested weekly for biochemical and proteome analyses using quantitative bidimensional electrophoresis (DiGE). Independent of the ozone treatment, all the analyses allowed a distinction between expanding and adult leaves. The results indicate that during the expansion phase (Days 0-7) the enzymatic machinery of the leaves is set up, and remains dynamically stable in the adult leaves (Days 14-28). Although ozone had no apparent effect on expanding leaves, the metabolic stability in fully expanded leaves observed in ozone-free plants was disturbed after 2 weeks of exposure and a stressinduced response became apparent.
Forests
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...
Canadian Journal of Forest Research-revue Canadienne De Recherche Forestiere, 1996
The effects of single-season tropospheric ozone (0,) exposures on growth, leaf abscission, and biomass of trembling aspen (Popu1u.s tremuloides Michx.) rooted cuttings and seedlings were studied. Plants were grown in the Upper Peninsula of Michigan in open-top chambers with 0, exposures that ranged from 7 to 92 ppm-h. Depending on the genotype, total seasonal 0, exposure in the range of 50-92 ppm-h had negative impacts on stem, retained leaf, and root biomass accumulation and on diameter growth. Leaf abscission generally increased with increasing 0, exposure and was the principal cause of the decrease in leaf biomass of the OX-treated plants. Considerable genetic variation in 0, responses occurred, as shown by differences in sensitivities among clones and among seedlings. However, the responses to 0, of rooted cuttings and seedlings were similar when seedling means were compared with clonal means for leaf abscission, diameter growth, retained leaf biomass, and root biomass. Comparison of a single square-wave treatment (52 ppm-h) with 70 and 92 ppm-h episodic exposures suggested that the plant response to the square-wave exposure was similar to the response to the highest episodic exposure even though the 92 ppm-h episodic exposure was almost twice the square-wave exposure. Our results are consistent with previous studies that show that I? tremuloides is highly responsive to 0, exposure and this response has a strong genetic component.