Physiological effects of ozone on cultivars of watermelon (Citrullus lanatus) and muskmelon (Cucumis melo) widely grown in Spain (original) (raw)
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Adverse effects of ambient ozone on watermelon yield and physiology at a rural site in Eastern Spain
New Phytologist, 1999
The study reported was conducted to establish the impacts of photochemical oxidants (primarily ambient ozone, O $ ) on the yield of watermelon (Citrullus lanatus) at a site on the east coast of Spain. Fruit yield and quality were monitored in plots established in a commercial watermelon field exposed, in open-top chambers (OTCs), to nonfiltered air (NFA ; near-ambient levels of ozone) or charcoal-filtered air (decreased levels of photochemical oxidants including O $ ; CFA), or to ambient air (AA), during the 1988 and 1989 growing seasons. Ambient levels of O $ were found to exceed present UN-ECE (United Nations Economic Commission for Europe ; Convention on Long-Range Transboundary Air Pollution) critical level guidelines for the protection of crop yield by approx. twofold in 1988 and by approx. fivefold in 1989. Plants exposed to NFA and AA developed visible O $ injury on the upper surface of sun-exposed older leaves, and fruit yield (annual marketable fruit weight and number) was found to be depressed in OTCs ventilated with NFA in comparison with those receiving CFA. Consistent with inter-annual variations in O $ exposure, greater yield losses were experienced in 1989 (39%) than in 1988 (19%), an effect mediated predominantly by a decline in fruit number rather than average fruit weight. Exposure to ambient levels of ozone also slightly decreased fruit quality (4-8% decline in soluble solids content). Leaf gas exchange measurements made in the field in 1988 revealed effects of O $ on fruit yield and quality to be associated with a decline in the net CO # assimilation rate per unit leaf area under light saturation (A sat ) and stomatal conductance to water vapour (g s ), and enhanced rates of dark respiration. A\c i curves (where A is the net CO # assimilation rate per unit leaf area and c i is the mole fraction of CO # in the leaf intercellular air space) constructed for plants grown in laboratory-based closed chambers, and exposed to an accumulated O $ exposure similar to that experienced by plants in the field, suggested that the likely cause of the decline in photosynthetic capacity was (1) a decrease in the amount and\or activity of Rubisco and (2) an impaired capacity for regeneration of ribulose 1,5bisphosphate, which was not mediated through changes in the photochemical efficiency of photosystem II (F v \F m , where F v is variable chlorophyll a fluorescence and F m is maximum chlorophyll a fluorescence). No shift in the relative stomatal limitation to photosynthesis was observed under the influence of O $ , suggesting that the decline in g s induced by the pollutant in both field and laboratory was the result, and not the cause, of the decrease in A sat . Ozone exposure also caused a decrease in C isotope discrimination (approx. 0.5=), a shift that revealed a departure from predicted theory based on supporting leaf gas exchange measurements. The study demonstrates that ambient levels of photochemical oxidants on the Spanish Mediterranean coast are high enough to adversely influence the yield and physiology of an economically important crop grown in the region, and the magnitude of the effects was
Italian Journal of Agronomy, 2008
An Open-Top Chamber experiment on two tomato cultivars (cv. Oxheart and cv. San Marzano) was carried out in Curno (Northern Italy) between June and September 2007. Two ozone treatments were applied for a 3.5 months period: Non-Filtered OTC (NF-OTC, 95% of ambient ozone) and Charcoal-Filtered OTC (CF-OTC, 50% of ambient ozone). Diurnal cycles of porometry measurements were performed during the season and allowed to draw a stomatal conductance model for each cultivar in order to calculate the ozone stomatal fluxes taken up by plants. Assessments on fruits yield were performed during the season, taking into account the number of fruits, their fresh weight and their marketability. In addition, measurements on the chlorophyll fluorescence of photosystems were carried out to assess possible negative effects on photosynthetic efficiency. Despite the two cultivars absorbed a similar ozone stomatal dose during the season (with an 8% difference), their responses to ozone treatments were totally divergent in relation to both fruits yield and photosynthetic efficiency. Plants of cv. Oxheart grown in NF-OTCs showed significant yield loss in the total weight of fruits (-35.9%) which is exclusively related to a decrease in the number of fruits produced (-35.7% of total fruits; -30.6% of marketable fruits), since mean fresh weight of fruits remained unaffected. Moreover the same plants displayed low values (in comparison to CF-OTCs plants) of the photosynthetic efficiency index (PI abs ) during the most intense period of ozone stress (July) occurred in the flowering stage of plants and at the beginning of fructification. Plants of the cv. San Marzano had an opposite response behaviour with an increase of the mean fresh weight of fruits in plants grown in NF-OTC (even if not statistically significant) and no difference in the number of fruits produced and in the values of photosynthetic efficiency.
Comparative ozone sensitivity of old and modern Greek cultivars of spring wheat
New Phytologist, 1990
Ten cultivars of spring wheat, hred and introduced in Greece hetween 1932 and 1980, were exposed to ozone (180/^g m"^) or to charcoal-filtered air (< 4/tg O3 m"^) for 21 d. Ozone sensitivity was assessed by recording the extent of visible injury, effects on mean relative growth rate {R) and changes in fast fluorescence kinetics. Ozone significantly (P<0-01) depressed the mean relative growth rate {R) and there were significant (P<0-01) differences in response hetween cultivars. Moreover, there was a highly significant (P < 0-002) negative relationship hetween the reduction in R and the year of introduction; the more modern the cultivar the greater its sensitivity to ozone. Ozone reduced root growth relative to the shoot, hut the effect varied with cultivar. Although all varieties developed typical visible symptoms of ozone damage, there was little relationship hetween the extent of this damage and effects on growth, or changes in fluorescence.
Photosynthetica, 2014
The crop sensitivity to ozone (O 3 ) is affected by the timing of the O 3 exposure, by the O 3 concentration, and by the crop age. To determine the physiological response to the acute ozone stress, tomato plants were exposed to O 3 at two growth stages. In Experiment I (Exp. I), O 3 (500 µg m -3 ) was applied to 30-d-old plants (PL30). In Experiment II (Exp. II), three O 3 concentrations (200, 350, and 500 µg m -3 ) were applied to 51-d-old plants (PL51). The time of the treatment was 4 h (7:30 -11:30 h). Photosynthesis and chlorophyll fluorescence measurements were done 4 times (before the exposure; 20 min, 20 h, and 2-3 weeks after the end of the treatment) using a LI-COR 6400 photosynthesis meter. The stomatal pore area and stomatal conductance were reduced as the O 3 concentration increased. Ozone induced the decrease in the photosynthetic parameters of tomato regardless of the plant age. Both the photosystem (PS) II operating efficiency and the maximum quantum efficiency of PSII photochemistry declined under the ozone stress suggesting that the PSII activity was inhibited by O 3 . The impaired PSII contributed to the reduced photosynthetic rate. The greater decline of photosynthetic parameters was found in the PL30 compared with the PL51. It proved the age-dependent ozone sensitivity of tomato, where the younger plants were more vulnerable. Ozone caused the degradation of photosynthetic apparatus, which affected the photosynthesis of tomato plants depending on the growth stage and the O 3 concentration. transport rate; F0 -minimal fluorescence of the dark-adapted leaf; F0' -minimal fluorescence of the light-adapted leaf; Fm -maximal fluorescence of the dark-adapted leaf; Fm' -maximal fluorescence of the light-adapted leaf; Fs -steady-state fluorescence; gs -stomatal conductance; Jmax -the maximum rate of carboxylation limited by electron transport rate for RuBP generation; NADPH -nicotinamide adenine dinucleotide phosphate; O200 -ozone treatment of 200 μg m -3 ; O350 -ozone treatment of 350 μg m -3 ; O500 -ozone treatment of 500 μg m -3 ; Pmax -light-saturated photosynthetic rate; PN -net photosynthetic rate; PL30 -30-d-old plants; PL51 -51-d-old plants; PPFD -photosynthetic photon flux density; PSphotosystem; qP -photochemical quenching coefficient; RD -dark-respiration rate; Rubisco -ribulose-1,5-bisphosphate carboxylase/ oxygenase; tb -before O3 treatment; t20m -20 min after O3 treatment; t20h -20 h after O3 treatment; t3w -2-3 weeks after O3 treatment; TPU -triose phosphate use; Vcmax -maximum carboxylation velocity of Rubisco; α -initial slope of the light curve at low PPFD; Θ -curve convexity; ΦCO2 -quantum yield of carboxylation rate; ФPSII -effective quantum yield of photosystem II photochemistry. Acknowledgements: The authors thank the Scholarship Foundation (French Embassy -Thailand International Cooperation Agency -Thailand Research Fund) for financial support.
Impact of Tropospheric Ozone on Crop Plants
Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2012
Tropospheric ozone (O 3 ) is the most important regional atmospheric pollutant causing risk to food production across the globe due to its phytotoxicity and prevalence over agricultural areas. Peak O 3 concentrations have declined in Europe and North America due to reductions in precursors during the last decades, however, emissions of O 3 precursors have increased in Asia. The current critical level of ozone is determined by the threshold for yield loss which is based on the seasonal sum of the external concentration above 40 ppb. In the present article, the impact of tropospheric O 3 on crop photosynthesis, defense mechanism, growth, reproductive processes and yield of crop plants have been documented. O 3 upon its entry into the leaf intercellular spaces rapidly forms reactive oxygen species and reacts with components of the leaf apoplast to initiate a complex set of responses that constitute variable countermeasures by antioxidative enzymes. Ozone affects photosynthetic process by influencing photosynthetic pigments, chlorophyll fluorescence kinetics and electron transport as well as carbon fixation in terms of decreased Rubisco activity and quantity. Translocation and allocation pattern of photosynthate also get influenced under O 3 , which affect reproductive processes and yield of crops. Plant species and cultivars exhibit a range of sensitivity to O 3 , which is identifiable in terms of biochemical, physiological, molecular and yield responses. Hence, understanding of cultivar sensitivity in context to O 3 would be helpful in development of potential O 3 biomarkers and O 3 tolerant variables.