Abstract
Aims Stipa purpurea is a dominant species of alpine grassland in northern Tibet, a region sensitive to climate change. Environmental variations in temperature, water and atmospheric carbon dioxide (CO2) concentration caused by regional climate change should affect the photosynthetic physiology of plants. Our objective was to investigate the response of S. purpurea to environmental variation. Methods We irrigated natural alpine grassland to imitate rainfall increasing soil moisture and then used a portable gas exchange system (LI-6400) to measure photosynthesis parameters at the irrigated field (H) and a natural field (CK). During measurement, we set three levels of leaf temperature (15, 20 and 25 °C) and gradually elevated CO2 concentration from 50 to 1 500 μmol·mol–1. Important findings CO2, temperature and soil moisture affected photosynthesis parameters of S. purpurea significantly, and interactions were apparent among these three factors. Rising CO2 gradually increased net photosynthetic rate (Pn) until it decreased at extremely high CO2. Higher temperature caused Pn to decrease, but sufficient water supply partially alleviated the negative effect. Sufficient water supply increased Pn. With rising CO2, intercellular CO2 concentration (Ci) increased, transpiration rate (Tr) decreased, water use efficiency (WUE) increased and stomatal conductance (Gs) decreased; higher temperature caused Gs to decrease faster. The photosynthesis parameters abovewere also impacted by the combined actions of humidity and temperature. Gs was maximized at 20 °C, and sufficient water supply increased Gs further. Ci increased with increased temperature, and this response was more pronounced with sufficient water. Tr was positively correlated with temperature and soil water. Vapor pressure deficit (VPD) was directly proportional to temperature and decreased with sufficient water. Increased temperature and increased water supply made WUE decline. Therefore, increased soil water had compensatory effects on the relationship between high temperature and photosynthetic parameters.
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Claims 20
Claim · model-written summary
CO2, temperature and soil moisture significantly affected photosynthesis parameters of Stipa purpurea, with interactions among the three factors.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- CO2, temperature and soil moisturee2
- Outcome
- photosynthesis parameterse2
Not reportedDirection
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“CO2, temperature and soil moisture affected photosynthesis parameters of S. purpurea significantly, and interactions were apparent among these three factors”
Claim · model-written summary
Rising CO2 increased the net photosynthetic rate of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- Rising CO2e2
- Outcome
- net photosynthetic rate (Pn)e2
- Direction
- increasede2
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“Rising CO2 gradually increased net photosynthetic rate (Pn) until it decreased at extremely high CO2”
Claim · model-written summary
At extremely high CO2 the net photosynthetic rate of Stipa purpurea decreased.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- extremely high CO2e2
- Outcome
- net photosynthetic rate (Pn)e2
- Direction
- decreasede2
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“Rising CO2 gradually increased net photosynthetic rate (Pn) until it decreased at extremely high CO2”
Claim · model-written summary
Higher temperature decreased the net photosynthetic rate (Pn) of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- Higher temperaturee3
- Outcome
- Pne3
- Direction
- decreasee3
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e3“Higher temperature caused Pn to decrease, but sufficient water supply partially alleviated the negative effect”
Claim · model-written summary
Sufficient water supply partially alleviated the negative effect of higher temperature on Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- sufficient water supplye3
- Outcome
- negative effecte3
- Direction
- partially alleviatede3
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e3“Higher temperature caused Pn to decrease, but sufficient water supply partially alleviated the negative effect”
Claim · model-written summary
Sufficient water supply increased the net photosynthetic rate of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- Sufficient water supplye4
- Outcome
- Pne4
- Direction
- increasede4
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e4“Sufficient water supply increased Pn”
Claim · model-written summary
Rising CO2 increased the intercellular CO2 concentration (Ci) of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- rising CO2e5
- Outcome
- intercellular CO2 concentration (Ci)e5
- Direction
- increasede5
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e5“With rising CO2, intercellular CO2 concentration (Ci) increased, transpiration rate (Tr) decreased, water use efficiency (WUE) increased and stomatal conductance (Gs) decreased”
Claim · model-written summary
Rising CO2 decreased the transpiration rate (Tr) of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- rising CO2e5
- Outcome
- transpiration rate (Tr)e5
- Direction
- decreasede5
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e5“With rising CO2, intercellular CO2 concentration (Ci) increased, transpiration rate (Tr) decreased, water use efficiency (WUE) increased and stomatal conductance (Gs) decreased”
Claim · model-written summary
Rising CO2 increased the water use efficiency (WUE) of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- rising CO2e5
- Outcome
- water use efficiency (WUE)e5
- Direction
- increasede5
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e5“With rising CO2, intercellular CO2 concentration (Ci) increased, transpiration rate (Tr) decreased, water use efficiency (WUE) increased and stomatal conductance (Gs) decreased”
Claim · model-written summary
Rising CO2 decreased the stomatal conductance (Gs) of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- rising CO2e5
- Outcome
- stomatal conductance (Gs)e5
- Direction
- decreasede5
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e5“With rising CO2, intercellular CO2 concentration (Ci) increased, transpiration rate (Tr) decreased, water use efficiency (WUE) increased and stomatal conductance (Gs) decreased”
Claim · model-written summary
Higher temperature made the stomatal conductance of Stipa purpurea decrease faster.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- higher temperaturee6
- Outcome
- Gse6
- Direction
- decrease fastere6
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e6“higher temperature caused Gs to decrease faster”
Claim · model-written summary
Stomatal conductance of Stipa purpurea was maximized at 20 °C.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- 20 °Ce7
- Outcome
- Gse7
- Direction
- maximizede7
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e7“Gs was maximized at 20 °C”
Claim · model-written summary
Sufficient water supply increased the stomatal conductance of Stipa purpurea further.
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“sufficient water supply increased Gs further”
Claim · model-written summary
Intercellular CO2 concentration of Stipa purpurea increased with increased temperature, more pronounced with sufficient water.
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“Ci increased with increased temperature, and this response was more pronounced with sufficient water”
Claim · model-written summary
Transpiration rate of Stipa purpurea was positively correlated with temperature and soil water.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- temperature and soil watere2
- Outcome
- Tre2
- Direction
- increaseinferrede2
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“Tr was positively correlated with temperature and soil water”
Claim · model-written summary
Vapor pressure deficit of Stipa purpurea was directly proportional to temperature.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- temperaturee2
- Outcome
- Vapor pressure deficit (VPD)e2
- Direction
- higherinferrede2
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“Vapor pressure deficit (VPD) was directly proportional to temperature and decreased with sufficient water”
Claim · model-written summary
Vapor pressure deficit of Stipa purpurea decreased with sufficient water.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- sufficient watere2
- Outcome
- Vapor pressure deficit (VPD)e2
- Direction
- decreasede2
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“Vapor pressure deficit (VPD) was directly proportional to temperature and decreased with sufficient water”
Claim · model-written summary
Increased temperature and increased water supply made water use efficiency of Stipa purpurea decline.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- Increased temperature and increased water supplye2
- Outcome
- WUEe2
- Direction
- declinee2
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“Increased temperature and increased water supply made WUE decline”
Claim · model-written summary
Increased soil water had compensatory effects on the relationship between high temperature and photosynthetic parameters of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- increased soil watere2
- Outcome
- relationship between high temperature and photosynthetic parameterse2
- Qualifier
- compensatory effectse2
Not reportedDirection
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“Therefore, increased soil water had compensatory effects on the relationship between high temperature and photosynthetic parameters”
Claim · model-written summary
The combined actions of humidity and temperature impacted the photosynthesis parameters of Stipa purpurea.
- Taxon
- Stipa purpureaStipa purpureat0
- Treatment
- combined actions of humidity and temperaturee2
- Outcome
- photosynthesis parameterse2
Not reportedDirection
Verbatim
t0“Stipa purpurea under irrigation in northern Tibet”
e2“The photosynthesis parameters abovewere also impacted by the combined actions of humidity and temperature”