Abstract
Environmental conditions influence plant responses to ozone (O(3)), but few studies have evaluated individual factors directly. In this study, the effect of O(3) at high and low atmospheric vapour pressure deficit (VPD) was evaluated in two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156) used as O(3) bioindicator plants. Plants were grown in outdoor controlled-environment chambers in charcoal-filtered air containing 0 or 60 nl l(-1) O(3) (12 h average) at two VPDs (1.26 and 1.96 kPa) and sampled for biomass, leaf area, daily water loss, and seed yield. VPD clearly influenced O(3) effects. At low VPD, O(3) reduced biomass, leaf area, and seed yield substantially in both genotypes, while at high VPD, O(3) had no significant effect on these components. In clean air, high VPD reduced biomass and yield by similar fractions in both genotypes compared with low VPD. Data suggest that a stomatal response to VPD per se may be lacking in both genotypes and it is hypothesized that the high VPD resulted in unsustainable transpiration and water deficits that resulted in reduced growth and yield. High VPD- and water-stress-induced stomatal responses may have reduced the O(3) flux into the leaves, which contributed to a higher yield compared to the low VPD treatment in both genotypes. At low VPD, transpiration increased in the O(3) treatment relative to the clean air treatment, suggesting that whole-plant conductance was increased by O(3) exposure. Ozone-related biomass reductions at low VPD were proportionally higher in S156 than in R123, indicating that differential O(3) sensitivity of these bioindicator plants remained evident when environmental conditions were conducive for O(3) effects. Assessments of potential O(3) impacts on vegetation should incorporate interacting factors such as VPD.
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Claims 7
Claim · model-written summary
At low VPD, ozone reduced biomass, leaf area and seed yield substantially in both snap bean genotypes.
Verbatim
e0“two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156)”
e1“At low VPD, O(3) reduced biomass, leaf area, and seed yield substantially in both genotypes”
e2“Plants were grown in outdoor controlled-environment chambers in charcoal-filtered air containing 0 or 60 nl l(-1) O(3)”
Claim · model-written summary
At high VPD, ozone had no significant effect on biomass, leaf area and seed yield.
Verbatim
e0“two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156)”
e1“At low VPD, O(3) reduced biomass, leaf area, and seed yield substantially in both genotypes”
e2“Plants were grown in outdoor controlled-environment chambers in charcoal-filtered air containing 0 or 60 nl l(-1) O(3)”
e3“while at high VPD, O(3) had no significant effect on these components”
Claim · model-written summary
In clean air, high VPD reduced biomass and yield in both snap bean genotypes compared with low VPD.
Verbatim
e0“two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156)”
e4“In clean air, high VPD reduced biomass and yield by similar fractions in both genotypes compared with low VPD”
Claim · model-written summary
High VPD is hypothesized to reduce snap bean growth and yield through unsustainable transpiration and water deficits.
Verbatim
e0“two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156)”
e5“it is hypothesized that the high VPD resulted in unsustainable transpiration and water deficits that resulted in reduced growth and yield”
Claim · model-written summary
At low VPD, ozone increased transpiration relative to clean air in snap bean.
Verbatim
e0“two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156)”
e6“At low VPD, transpiration increased in the O(3) treatment relative to the clean air treatment”
Claim · model-written summary
Ozone-related biomass reductions at low VPD were proportionally higher in genotype S156 than in R123.
Verbatim
e0“two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156)”
e7“Ozone-related biomass reductions at low VPD were proportionally higher in S156 than in R123”
Claim · model-written summary
Assessments of potential ozone impacts on vegetation should incorporate interacting factors such as VPD.
Verbatim
t0“ozone responses of snap bean (Phaseolus vulgaris L.) genotypes”
e7“Assessments of potential O(3) impacts on vegetation should incorporate interacting factors such as VPD”
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See all 6 papers →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.