Abstract
summary Ozone (O 3 ) in ambient air was investigated as a possible cause of visible damage to leaves of white clover ( Trifolium repens L.) in agricultural areas of Switzerland. Differences in the sensitivity of five commonly mown cultivars were studied, namely Ladino Sacramento, Ladino California, Alban, Sonja and Milkanova. Plants were grown in pots and exposed to O 3 using three different experimental systems: (i) exposure to ambient air, (ii) exposure in open‐top chambers to filtered air, unfiltered air, or unfiltered air to which O 3 was added from 09.00 until 17.00 h during a four‐day period, (iii) exposure under controlled environmental condition to filtered air with or without O 3 added daily. Occurrence of injury symptoms on field‐grown plants was recorded during the summers of 1987 and 1988. Ozone exposure produced visible injury expressed as small necrotic flecks on the tipper leaf surface. Irrespective of the experimental system used, the following order in O 3 sensitivity was observed: L. Sacramento ≤ L. California ≪ Alban ≤ Sonja ≤ Milkanova. Injury symptoms were seen when plants were exposed to ambient O 3 or to unfiltered air in open‐top chambers, but not in charcoal‐filtered air. In ambient air, symptoms in the most sensitive cultivars appeared after episodes with 1‐h maximum concentrations of above 120‐140μg m −3 occurring on several consecutive days. The symptoms of injury could be reproduced in controlled‐environment fumigation experiments using concentrations comparable to those observed in ambient air. Plants of the different cultivars grown under controlled environmental conditions did not differ in superoxide dismutase or peroxidase activity, or in the content of fructose, sucrose or glucose. Differences in O 3 −sensitivity between cultivars were related to differences in stomatal density and to some degree to the length of the stomatal pore. Stomatal densities were related to leaf conductance, transpiration, and rate of water loss by excised leaves. Leaves of Milkanova (resistant) had higher 3 13 values than L. California (sensitive). Compared with filtered air, exposure to unfiltered ambient air or O 3 –amended air in open‐top chambers caused a change in δ 13 value in leaves of L. California (sensitive), but not in leaves of Milkanova (resistant). It is concluded that ambient levels of O 3 in Switzerland can be sufficient to produce visible leaf injury in sensitive white clover cultivars characterized by a high gas‐phase conductance of the leaves, that the isotopic composition of leaf tissue could be used as an indicator of O 3 sensitivity in different cultivars, and that ambient levels of O 3 can change the isotopic composition of the leaf tissue in sensitive species.
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Claims 12
Claim · model-written summary
Ozone exposure produced necrotic flecks on white clover leaves.
- Taxon
- white clover
Trifolium repense1 - Organ / stage
- leaf surfacee0
- Treatment
- Ozone exposuree0
- Outcome
- visible injury expressed as small necrotic fleckse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone exposure produced visible injury expressed as small necrotic flecks on the tipper leaf surface.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
The five cultivars differed in ozone sensitivity, ordered from L. Sacramento to Milkanova.
- Taxon
- white cloverTrifolium repense1
- Material
- L. Sacramento ≤ L. California ≪ Alban ≤ Sonja ≤ Milkanovae0
- Outcome
- O 3 sensitivitye0
- Direction
- following ordere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the following order in O 3 sensitivity was observed: L. Sacramento ≤ L. California ≪ Alban ≤ Sonja ≤ Milkanova.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Injury occurred under ambient ozone or unfiltered air but not charcoal-filtered air.
- Taxon
- white cloverTrifolium repense1
- Treatment
- ambient O 3 or to unfiltered aire0
- Outcome
- Injury symptomse0
- Comparator
- charcoal‐filtered aire0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Injury symptoms were seen when plants were exposed to ambient O 3 or to unfiltered air in open‐top chambers, but not in charcoal‐filtered air.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Sensitive cultivars developed symptoms after consecutive days with 1-hour ozone maxima above 120–140 μg m−3.
- Taxon
- white cloverTrifolium repense1
- Outcome
- symptomse0
- Value
- above 120‐140μg m −3e0
- Qualifier
- occurring on several consecutive dayse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“symptoms in the most sensitive cultivars appeared after episodes with 1‐h maximum concentrations of above 120‐140μg m −3 occurring on several consecutive days.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Controlled-environment fumigation reproduced the injury symptoms at concentrations comparable to ambient air.
- Taxon
- white cloverTrifolium repense1
- Treatment
- controlled‐environment fumigatione0
- Outcome
- symptoms of injurye0
- Comparator
- ambient aire0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The symptoms of injury could be reproduced in controlled‐environment fumigation experiments using concentrations comparable to those observed in ambient air.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Cultivars did not differ in superoxide dismutase or peroxidase activity or fructose content.
- Taxon
- white cloverTrifolium repense1
- Outcome
- superoxide dismutase or peroxidase activity, or in the content of fructosee0
- Direction
- did not differe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants of the different cultivars grown under controlled environmental conditions did not differ in superoxide dismutase or peroxidase activity, or in the content of fructose, sucrose or glucose.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Cultivars did not differ in sucrose or glucose content.
- Taxon
- white cloverTrifolium repense1
- Outcome
- sucrose or glucosee0
- Direction
- did not differe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants of the different cultivars grown under controlled environmental conditions did not differ in superoxide dismutase or peroxidase activity, or in the content of fructose, sucrose or glucose.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Ozone sensitivity differences were related to stomatal density and somewhat to stomatal pore length.
- Taxon
- white cloverTrifolium repense1
- Organ / stage
- stomatal poree0
- Outcome
- O 3 −sensitivitye0
- Qualifier
- stomatal densitye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Differences in O 3 −sensitivity between cultivars were related to differences in stomatal density and to some degree to the length of the stomatal pore.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Stomatal density was related to leaf conductance, transpiration, and excised-leaf water loss.
- Taxon
- white cloverTrifolium repense1
- Organ / stage
- excised leavese0
- Outcome
- leaf conductance, transpiration, and rate of water loss by excised leavese0
- Qualifier
- Stomatal densitiese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stomatal densities were related to leaf conductance, transpiration, and rate of water loss by excised leaves.”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Milkanova leaves had higher 3 13 values than L. California leaves.
- Taxon
- white cloverTrifolium repense1
- Material
- Milkanovae0
- Outcome
- 3 13 valuese0
- Direction
- highere0
- Comparator
- L. Californiae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaves of Milkanova (resistant) had higher 3 13 values than L. California (sensitive).”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Unfiltered or ozone-amended air changed leaf δ 13 in L. California relative to filtered air.
- Taxon
- white cloverTrifolium repense1
- Material
- L. Californiae0
- Treatment
- unfiltered ambient air or O 3 –amended aire0
- Outcome
- δ 13 valuee0
- Comparator
- filtered aire0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with filtered air, exposure to unfiltered ambient air or O 3 –amended air in open‐top chambers caused a change in δ 13 value in leaves of L. California (sensitive), but not in leaves of Milkanova (resistant).”
e1“white clover ( Trifolium repens L.)”
Claim · model-written summary
Unfiltered or ozone-amended air did not change leaf δ 13 in Milkanova relative to filtered air.
- Taxon
- white cloverTrifolium repense1
- Material
- Milkanovae0
- Treatment
- unfiltered ambient air or O 3 –amended aire0
- Outcome
- δ 13 valuee0
- Comparator
- filtered aire0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with filtered air, exposure to unfiltered ambient air or O 3 –amended air in open‐top chambers caused a change in δ 13 value in leaves of L. California (sensitive), but not in leaves of Milkanova (resistant).”
e1“white clover ( Trifolium repens L.)”
The same questions in other papers
ozone · crop injury · Trifolium repens (white clover)Results agree
2 papers in the same direction as this paper
- negative
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.