Abstract
Cherry seedlings ( Prunus avium ) were grown from seed for two growing seasons in three ambient [CO 2 ] (∼350 μmol mol −1 ) and three elevated [CO 2 ] (ambient+∼350 μmol mol −1 ) open‐top chambers, and in three outside blocks. A drying cycle was imposed in both the growing seasons to half the seedlings: days 69–115 in the first growing season, and in the second growing season days 212–251 on the same seedlings which had already experienced drought. Stomatal conductance was significantly reduced in elevated [CO 2 ]‐grown, unstressed seedlings in both the first and second growing seasons, but was not caused by a decrease in stomatal density. Droughted seedlings showed little or no reduction in stomatal conductance in response to elevated [CO 2 ]. However, stomatal conductance was highly correlated with soil water status. Photosynthetic rate increased significantly in response to elevated [CO 2 ] in both water regimes, leading to improvement in instantaneous transpiration efficiency over the whole duration of the experiment, but there was no relationship between instantaneous transpiration efficiency and long‐term water use efficiency. The A max was strongly reduced in the second growing season, but unaffected by [CO 2 ] treatment. Although photosynthetic rate was not down‐regulated, Rubisco activity was decreased by elevated [CO 2 ], possibly because of the increased leaf carbon: nitrogen ratio which had occurred by the ends of the two growing seasons. Elevated [CO 2 ] did not improve plant water relations (for example, bulk leaf – water potential, osmotic potentials at full and zero turgor, relative water content at zero turgor, bulk modulus of elasticity of the cell) and thus did not increase water‐stress tolerance of cherry seedlings.
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Claims 13
Claim · model-written summary
Elevated CO2 significantly reduced stomatal conductance in unstressed cherry seedlings in both seasons.
- Taxon
- Cherryt0
- Treatment
- elevated [CO 2 ]e0
- Outcome
- Stomatal conductancee0
- Direction
- reducede0
- Qualifier
- unstressed seedlings in both the first and second growing seasonse0
Not reportedComparator
Verbatim
e0“Stomatal conductance was significantly reduced in elevated [CO 2 ]‐grown, unstressed seedlings in both the first and second growing seasons”
t0“cherry (Prunus avium)”
Claim · model-written summary
The stomatal conductance reduction was not caused by reduced stomatal density.
Verbatim
e0“but was not caused by a decrease in stomatal density”
t0“cherry (Prunus avium)”
Claim · model-written summary
Droughted seedlings showed little or no stomatal conductance reduction under elevated CO2.
- Taxon
- cherryt0
- Treatment
- elevated [CO 2 ]e0
- Outcome
- stomatal conductancee0
- Direction
- little or no reductione0
- Qualifier
- Droughted seedlingse0
Not reportedComparator
Verbatim
e0“Droughted seedlings showed little or no reduction in stomatal conductance in response to elevated [CO 2 ]”
t0“cherry (Prunus avium)”
Claim · model-written summary
Stomatal conductance was highly correlated with soil water status.
Not reportedTreatmentSettingDirection
Verbatim
e0“stomatal conductance was highly correlated with soil water status”
t0“cherry (Prunus avium)”
Claim · model-written summary
Elevated CO2 significantly increased photosynthetic rate under both water regimes.
- Taxon
- cherryt0
- Treatment
- elevated [CO 2 ]e0
- Outcome
- Photosynthetic ratee0
- Direction
- increasede0
- Qualifier
- both water regimese0
Not reportedComparator
Verbatim
e0“Photosynthetic rate increased significantly in response to elevated [CO 2 ] in both water regimes”
t0“cherry (Prunus avium)”
Claim · model-written summary
Elevated CO2 improved instantaneous transpiration efficiency throughout the experiment.
- Taxon
- cherryt0
- Treatment
- elevated [CO 2 ]e1
- Outcome
- instantaneous transpiration efficiencye0
- Direction
- improvemente0
- Qualifier
- over the whole duration of the experimente0
Not reportedComparator
Verbatim
e0“leading to improvement in instantaneous transpiration efficiency over the whole duration of the experiment”
t0“cherry (Prunus avium)”
e1“Stomatal conductance was significantly reduced in elevated [CO 2 ]‐grown, unstressed seedlings in both the first and second growing seasons”
Claim · model-written summary
Instantaneous transpiration efficiency was unrelated to long-term water use efficiency.
Verbatim
e0“there was no relationship between instantaneous transpiration efficiency and long‐term water use efficiency”
t0“cherry (Prunus avium)”
Claim · model-written summary
A max was strongly reduced in the second growing season.
Verbatim
e0“The A max was strongly reduced in the second growing season”
t0“cherry (Prunus avium)”
Claim · model-written summary
CO2 treatment did not affect A max.
Not reportedComparator
Verbatim
e0“but unaffected by [CO 2 ] treatment”
t0“cherry (Prunus avium)”
e1“The A max was strongly reduced in the second growing season”
Claim · model-written summary
Elevated CO2 decreased Rubisco activity.
Not reportedComparator
Verbatim
e0“Rubisco activity was decreased by elevated [CO 2 ]”
t0“cherry (Prunus avium)”
Claim · model-written summary
Leaf carbon:nitrogen ratio increased by the end of both seasons.
Verbatim
e0“the increased leaf carbon: nitrogen ratio which had occurred by the ends of the two growing seasons”
t0“cherry (Prunus avium)”
Claim · model-written summary
Elevated CO2 did not improve cherry plant water relations.
Not reportedComparator
Verbatim
e0“Elevated [CO 2 ] did not improve plant water relations (for example, bulk leaf – water potential, osmotic potentials at full and zero turgor, relative water content at zero turgor, bulk modulus of elasticity of the cell)”
t0“cherry (Prunus avium)”
Claim · model-written summary
Elevated CO2 did not increase water-stress tolerance of cherry seedlings.
Not reportedComparator
Verbatim
e0“thus did not increase water‐stress tolerance of cherry seedlings”
t0“Elevated [CO 2 ]”