Abstract
Through stimulation of root growth, increasing atmospheric CO2 concentration ([CO2]) may facilitate access of crops to sub-soil water, which could potentially prolong physiological activity in dryland environments, particularly because crops are more water use efficient under elevated [CO2] (e[CO2]). This study investigated the effect of drought in shallow soil versus sub-soil on agronomic and physiological responses of wheat to e[CO2] in a glasshouse experiment. Wheat (Triticum aestivum L. cv. Yitpi) was grown in split-columns with the top (0-30 cm) and bottom (31-60 cm; 'sub-soil') soil layer hydraulically separated by a wax-coated, root-penetrable layer under ambient [CO2] (a[CO2], ∼400 μmol mol-1) or e[CO2] (∼700 μmol mol-1) [CO2]. Drought was imposed from stem-elongation in either the top or bottom soil layer or both by withholding 33% of the irrigation, resulting in four water treatments (WW, WD, DW, DD; D = drought, W = well-watered, letters denote water treatment in top and bottom soil layer, respectively). Leaf gas exchange was measured weekly from stem-elongation until anthesis. Above-and belowground biomass, grain yield and yield components were evaluated at three developmental stages (stem-elongation, anthesis and maturity). Compared with a[CO2], net assimilation rate was higher and stomatal conductance was lower under e[CO2], resulting in greater intrinsic water use efficiency. Elevated [CO2] stimulated both above- and belowground biomass as well as grain yield, however, this stimulation was greater under well-watered (WW) than drought (DD) throughout the whole soil profile. Imposition of drought in either or both soil layers decreased aboveground biomass and grain yield under both [CO2] compared to the well-watered treatment. However, the greatest 'CO2 fertilisation effect' was observed when drought was imposed in the top soil layer only (DW), and this was associated with e[CO2]-stimulation of root growth especially in the well-watered bottom layer. We suggest that stimulation of belowground biomass under e[CO2] will allow better access to sub-soil water during grain filling period, when additional water is converted into additional yield with high efficiency in Mediterranean-type dryland agro-ecosystems. If sufficient water is available in the sub-soil, e[CO2] may help mitigating the effect of drying surface soil.
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Claims 11
Claim · model-written summary
Elevated CO2 increased net assimilation rate.
- Taxon
- wheat
Triticum aestivumt0 - Outcome
- net assimilation ratee0
- Direction
- highere0
- Comparator
- a[CO2]e0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with a[CO2], net assimilation rate was higher”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
Elevated CO2 lowered stomatal conductance.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- e[CO2]e0
- Outcome
- stomatal conductancee0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stomatal conductance was lower under e[CO2]”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
Elevated CO2 increased intrinsic water use efficiency.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- e[CO2]e0
- Outcome
- intrinsic water use efficiencye0
- Direction
- greatere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under e[CO2], resulting in greater intrinsic water use efficiency”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
Elevated CO2 stimulated aboveground biomass.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Elevated [CO2]e0
- Outcome
- above-e0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated [CO2] stimulated both above- and belowground biomass as well as grain yield”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
Elevated CO2 stimulated belowground biomass.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Elevated [CO2]e0
- Outcome
- belowground biomasse0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated [CO2] stimulated both above- and belowground biomass as well as grain yield”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
Elevated CO2 stimulated grain yield.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Elevated [CO2]e0
- Outcome
- grain yielde0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated [CO2] stimulated both above- and belowground biomass as well as grain yield”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
CO2 stimulation was greater in well watered than fully droughted soil.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- well-watered (WW)e0
- Outcome
- stimulatione0
- Direction
- greatere0
- Comparator
- drought (DD)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this stimulation was greater under well-watered (WW) than drought (DD) throughout the whole soil profile”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
Drought in either or both layers decreased aboveground biomass.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- drought in either or both soil layerse0
- Outcome
- aboveground biomasse0
- Direction
- decreasede0
- Comparator
- well-watered treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Imposition of drought in either or both soil layers decreased aboveground biomass and grain yield under both [CO2] compared to the well-watered treatment”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
Drought in either or both layers decreased grain yield.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- drought in either or both soil layerse0
- Outcome
- grain yielde0
- Direction
- decreasede0
- Comparator
- well-watered treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Imposition of drought in either or both soil layers decreased aboveground biomass and grain yield under both [CO2] compared to the well-watered treatment”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
The greatest CO2 fertilisation effect occurred with drought only in topsoil.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- drought was imposed in the top soil layer only (DW)e0
- Outcome
- CO2 fertilisation effecte0
- Direction
- greateste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the greatest 'CO2 fertilisation effect' was observed when drought was imposed in the top soil layer only (DW)”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
Claim · model-written summary
Elevated CO2 stimulated root growth especially in the watered bottom layer.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- e[CO2]e0
- Outcome
- root growthe0
- Direction
- stimulatione0
- Qualifier
- well-watered bottom layere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“e[CO2]-stimulation of root growth especially in the well-watered bottom layer”
t0“Wheat (Triticum aestivum L. cv. Yitpi)”
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