Claim · model-written summary
At low soil water potential, photosynthesis and transpiration declined less steeply from daily maxima, with small max-min differences.
- Taxon
- Picea abies
Picea abiest0 - Outcome
- rates of photosynthesis and transpiratione0
- Direction
- decreased less steeplye0
- Qualifier
- differences between maxima and minima were smalle0
- Setting
- soil water potential was lower than -2000 hPae1
Not reportedMaterialGeneCompoundOrgan / stageInteractorInteractor roleSecond interactorSecond interactor roleTreatmentComparatorValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under these conditions, rates of photosynthesis and transpiration decreased less steeply from the daily maxima and differences between maxima and minima were small.”
e1“When soil water potential was lower than -2000 hPa”
t0“Picea abies”
Title
U. Maier-Maercker Tree Physiology 1998. doi:10.1093/treephys/18.4.211
Other claims from this paper (11)
- Observation Early in drought, daily maximum photosynthesis and transpiration were relatively high.
- Association As humidity fell during the day, gas exchange dropped more steeply and earlier on successive drought days.
- Association Maximum stomatal aperture was greatly reduced below a soil water potential of -2000 hPa, despite humid air.
- Association In the field, daily transpiration and photosynthesis sums depended more on atmospheric conditions than soil water potential.
- Association In growth chambers, daily transpiration and photosynthesis sums fell continuously as soil dried, steeply to -2000 hPa and then slowly.
- Observation Predawn water potential fluctuated in the field but tended to fall over time.
- Observation Needle osmotic potential increased slightly over time in the field.
- Observation Growth chamber predawn water potential never exceeded -1.0 MPa despite saturated soil.
- Association With high average humidity, relatively high predawn water potential persisted until soil water potential reached -8000 hPa.
- Mechanism The authors explain diurnal trends by interdependence of leaf conductance and water potential.
- Mechanism The authors state that stomata respond directly to the ratio of water supply to demand.