Abstract
Rising atmospheric [CO2] is associated with increased air temperature, and this warming may drive many rare plant species to extinction. However, to date, studies on the interactive effects of rising [CO2] and warming have focussed on just a few widely distributed plant species. Wollemi pine (Wollemia nobilis W.G.Jones, K.D.Hill, & J.M.Allen), formerly widespread in Australia, was reduced to a remnant population of fewer than 100 genetically indistinguishable individuals. Here, we examined the interactive effects of three [CO2] (290, 400 and 650ppm) and two temperature (ambient, ambient+4°C) treatments on clonally-propagated Wollemi pine grown for 17 months in glasshouses under well-watered and fertilised conditions. In general, the effects of rising [CO2] and temperature on growth and physiology were not interactive. Rising [CO2] increased shoot growth, light-saturated net photosynthetic rates (Asat) and net carbon gain. Higher net carbon gain was due to increased maximum apparent quantum yield and reduced non-photorespiratory respiration in the light, which also reduced the light compensation point. In contrast, increasing temperature reduced stem growth and Asat. Compensatory changes in mesophyll conductance and stomatal regulation suggest a narrow functional range of optimal water and CO2 flux co-regulation. These results suggest Asat and growth of the surviving genotype of Wollemi pine may continue to increase with rising [CO2], but increasing temperatures may offset these effects, and challenges to physiological and morphological controls over water and carbon trade-offs may push the remnant wild population of Wollemi pine towards extinction.
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Claims 9
Claim · model-written summary
CO2 and temperature effects on growth and physiology were generally not interactive.
WollemiaNot reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In general, the effects of rising [CO2] and temperature on growth and physiology were not interactive.”
t0“Wollemi pine”
Claim · model-written summary
Rising CO2 increased shoot growth, light-saturated net photosynthetic rates, and net carbon gain.
- Treatment
- Rising [CO2]e0
- Outcome
- shoot growth, light-saturated net photosynthetic rates (Asat) and net carbon gaine0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rising [CO2] increased shoot growth, light-saturated net photosynthetic rates (Asat) and net carbon gain.”
t0“Wollemi pine”
Claim · model-written summary
Higher net carbon gain was attributed to increased maximum apparent quantum yield and reduced respiration in the light.
- Outcome
- net carbon gaine0
- Direction
- Highere0
- Qualifier
- increased maximum apparent quantum yield and reduced non-photorespiratory respiration in the lighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Higher net carbon gain was due to increased maximum apparent quantum yield and reduced non-photorespiratory respiration in the light, which also reduced the light compensation point.”
t0“Wollemi pine”
Claim · model-written summary
Rising CO2 increased maximum apparent quantum yield.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Higher net carbon gain was due to increased maximum apparent quantum yield and reduced non-photorespiratory respiration in the light, which also reduced the light compensation point.”
e1“Rising [CO2] increased shoot growth, light-saturated net photosynthetic rates (Asat) and net carbon gain.”
t0“Wollemi pine”
Claim · model-written summary
Rising CO2 reduced non-photorespiratory respiration in the light and the light compensation point.
- Treatment
- Rising [CO2]e1
- Outcome
- non-photorespiratory respiration in the lighte0
- Direction
- reducede0
- Qualifier
- also reduced the light compensation pointe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Higher net carbon gain was due to increased maximum apparent quantum yield and reduced non-photorespiratory respiration in the light, which also reduced the light compensation point.”
e1“Rising [CO2] increased shoot growth, light-saturated net photosynthetic rates (Asat) and net carbon gain.”
t0“Wollemi pine”
Claim · model-written summary
Increasing temperature reduced stem growth and Asat.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In contrast, increasing temperature reduced stem growth and Asat.”
t0“Wollemi pine”
Claim · model-written summary
Compensatory mesophyll conductance and stomatal regulation changes suggest a narrow optimal range of water and CO2 flux co-regulation.
- Outcome
- a narrow functional range of optimal water and CO2 flux co-regulatione0
- Qualifier
- Compensatory changes in mesophyll conductance and stomatal regulatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compensatory changes in mesophyll conductance and stomatal regulation suggest a narrow functional range of optimal water and CO2 flux co-regulation.”
t0“Wollemi pine”
Claim · model-written summary
The surviving genotype may increase Asat and growth with rising CO2, but warming may offset these effects.
- Treatment
- rising [CO2]e0
- Outcome
- Asat and growthe0
- Qualifier
- increasing temperatures may offset these effectse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These results suggest Asat and growth of the surviving genotype of Wollemi pine may continue to increase with rising [CO2], but increasing temperatures may offset these effects”
Claim · model-written summary
Challenges to water and carbon trade-off controls may push the remnant wild population toward extinction.
- Outcome
- extinctione0
- Qualifier
- challenges to physiological and morphological controls over water and carbon trade-offse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“challenges to physiological and morphological controls over water and carbon trade-offs may push the remnant wild population of Wollemi pine towards extinction.”