Table 2.
Summary of effects of Elevated CO2 and drought in plants.
| Plant/Crop/Tree | CO2 Concentration | Water Stress Imposition | Effect | Reference |
|---|---|---|---|---|
| Poplar (Populus spp.) | 700 ± 50 µmol mol−1 | Soil drying cycle by withholding water | Reduced Gas exchange, decreased leaf conductance, increased photosynthesis, increased transpiration efficiency | [12] |
| Wheat (Triticum aestivum) | 400 μmol mol−1, 790 μmol mol−1 | Progressive restriction of water from 10 percent to 60 percent pot capacity | Reduced plant biomass, Stomatal conductance and carbon isotope signature indicated water saving strategy. PEPC expression increased |
[72] |
| Tabernaemontana divaricata | 1000 μmol mol−1, 700 μmol mol−1 | 70 percent of field capacity (FC) for 4 days and 30 percent of FC for 4 days | Increase in stomatal conductance (gs), plant height (PH) and plant girth (PG) | [82] |
| Maize (Zea mays) | 550 μmol mol−1 | Half water in water stress treatment compared to control | 37 percent reduction in whole plant transpiration | [43] |
| Napier grass (Pennisetum purpureum Schumach × Pennisetum glaucum (L.) R. Br) and hydric common reed grass (Phragmites australis (Cav.) Trin. Ex Steud) | 563 ± 6.7 μmol mol−1 541 ± 6.9 μmol mol−1 601 ± 9.1 μmol mol−1 |
Withdrawing irrigation | Increase in Photosynthesis, reduced leaf water potential and increase in transpiration | [44] |
| Maize (Zea mays) | 700 μmol mol−1, 900 μmol mol−1, and 1200 μmol mol−1 | deficit irrigation | Decreases in stomatal conductance and reduced transpiration rate | [45] |
| Soyabean (Glycine max) | Ambient + 200 μmol mol−1 | 35–45 percent of RWC | Elevated CO2 enhanced the resistance to drought by improving the capacity of photosynthesis and WUE in soybean leaves | [46] |
| Pinus halepensis (Aleppo pine) | 867 ± 157 μmol mol−1 | 10 Percent Relative Substrate Water Content | Under drought, the effect of CO2 on WUE was pronounced, with intercellular CO2 being increased near stomatal closure | [83] |
| Lemon (Citrus limon) | 650 and 850 μmol mol−1 | leaf water potential of −3.5 MPa | Stomatal downregulation at elevated CO2 reduced water-use but not photosynthesis. | [84] |
| Soybean (Glycine max) | 800 μmol mol−1 | water deficit was applied by randomly moving plants out of the hydroponic solution exposing the roots to ambient- or elevated-air |
Responses of soybean roots to short-term water deficit are buffered by Elevated CO2 | [47] |
| Cassava (Manihot esculenta Crantz) | 750 μmol mol−1 | Stopping irrigation for 7 days | Elevated CO2 reduced the negative effect of drought on transpiration, water use efficiency, all growth measures and harvest index. |
[85] |
| Faba bean (Vicia faba L.) | 550 μmol mol−1 | Water was withheld until 30 percent FC | Elevated CO2-induced stimulation of nodulation and nodule density helped maintain N2 fixation under drought | [86] |
| Andiroba (Carapa surinamensis) | 700 μmol mol−1 | 50 percent field capacity | Whole-plant water-use efficiency (WUE) improved under combination treatments | [87] |
| Hymenaea stigonocarpa Mart. ex Hayne, Solanum lycocarpum A. St.-Hil. and Tabebuia aurea (Silva Manso) Benth. and Hook. f. ex S. Moore | 700 μmol mol−1 | Water stress was introduced three times during the experiment by halting irrigation 1 month before the fourth (360 days old), fifth (450 days old) and sixth (540 days old) morphophysiological surveys |
Water stress decreased biomass production under high CO2 | [88] |
| Grapevines (Vitis labrusca) | 800 μmol mol−1 | Stopping irrigation | Elevated CO2 delayed drought effects on both net photosynthetic rate and Rubisco activity for four days, by reducing stomatal conductance, transpiration, and stomatal density | [89] |
| Brassica napus | 800 μmol mol−1 | Withholding water for 7 days | Elevated CO2 diminished the adverse effect by improved water relations | [52] |
| Maize (Zea mays) | 550, 700, and 900 μmol mol−1 | Deficit irrigation | Photosynthetic rate in elevated CO2 concentrations was higher under Deficit irrigation than under regular irrigation. | [90] |
| Acrocomia aculeata | 700 μmol mol−1 | Water withholding | Higher Rubisco carboxylation rate (Vc max) and electron transport rate (J max) contributed to recovery from drought | [56] |
| Cucumber (Cucumis sativus L.) | 800 ± 20 μmol mol−1 | ψw = −0.05 MPa and ψw = −0.15 with PEG 6000 | Higher photosynthetic performance and increased grana thickness under moderate drought stress, increased palisade cells length and chloroplasts number per palisade cell under severe drought stress. |
[91] |