Table 1.

Physiological trait alterations under elevated CO₂ conditions along with other stress responses in selected legumes and other key crop species.

Crop	Stress imposed (CO2 level and others)	Trait [increased (↑), decreased (↓), not affected (-)]	Reference
Soybean	aCO2 (ambient CO2) of 390 ppm or eCO2 (elevated CO2) of 550 ppm	Nodule number per plant (↑), nodule fresh weight per plant (↑), nodule density (↑), single nodule N fixation (↑), seed yield (↑), proportion of remobilized N in seeds (↓) and shoot N concentration (↓)	[29]
	eCO2 of 550 ± 30 ppm and aCO2 of 390 ± 30 ppm	At mature stage: Protein content (↓), fatty acid content (↑), total free amino acid (↓) total and specific isoflavons (↑), concentrations of potassium (K), calcium (Ca), magnesium (Mg), phosphorous (P) and sulphur (S) (↓), zinc (Zn), iron (Fe) (↓) and Mg, S, and Ca (↑)	[98]
Mung bean	400 or 700 μmol/mol CO2+heat + ABA	Above ground biomass (↑), growth indices (↑), nitrogen balance index (NBI) (↑), flavonoids (↑), shoot/root mass ratio (↑) and chlorophyll (↓)	[99]
	eCO2 levels of 550 and 700 μL/L	Plant height (↑), leaf area (↑), total dry matter (↑), pod and seed yields (↑)	[53]
Peanut	CO2 levels: 400 ppm and 700 ppm	Total biomass (↑) and final seed yield (↓)	[100]
	Temperatures: 33/21 °C (TA), 35.5/23.5 °C and 38/26 °C
	CO2 levels of 375 ppm and 700 ppm + Temp: 28 °C and 32 °C	Transpiration equivalent (↑)	[101]
Field pea	aCO2 level of 390 ppm or eCO2 of 550 ppm with N treatments by adding Ca(15NO3)2 at either 10 (Low N) or 25 (High N) mg N/kg soil.	Root dry weight (↑), shoot dry weight (↑), root shoot ratio (↓), biomass (↑), soil nitrogen (↓), nodule mass and size (↑) and leghemoglobin content (↓)	[8]
Rice	aCO2 of 374-386 μmol/mol or eCO2 of 571, 588 and 590 μmol/mol	Grain protein (↓), grain micronutrients (↓), Fe and Zn concentrations (↓) and vitamin content (↓)	[102]
Wheat	CO2 above normal levels (365 μmol/mol) and FACE (186 μmol/mol) above ambient + two levels of soil nitrogen supply (350 and 15 kg/ha of nitrogen, NH4NO3, applied in the irrigation water)	Total activity of ribulose-1,5-bisphosphate carboxylase/ oxygenase (Rubisco) (↑), leaf content of Rubisco (↑) and Light Harvesting Chlorophyll a/b protein associated with Photosystem II (LHC II) (↑)	[103]
Wheat, ryegrass, clover, potato, grape, rice, barley, sugar beet, soybean, cassava, rapeseed, mustard, coffee (C3 crops) and sorghum and maize (C4 crops)	aCO2 of 353 ppm and eCO2 of 550 ppm	Shoot biomass (↑), evapotranspiration (↓), biomass (↑), yield (↑) and canopy temperature (↑)	[3]
Quinoa	aCO2 of 400 and eCO2 of 600 μmol/mol at 20/14 °C day/night temperature, with or without exposure to day/night temperatures of 35/29 °C (“high”) for seven days during anthesis	Leaf photosynthesis and stomatal conductance (↓), Harvest index (↑) and total dry biomass (↑)	[104]
Chinese yam	aCO2 and eCO2 (ambient +200 μmol/mol) and two mean air temperatures of 22.2 °C and 25.6 °C	Plant growth and vigor (↑), dry weight (↑) and germination percentage (↑)	[105]
Potato, tomato, lettuce and other vegetables	aCO2 of ≥200 and ≤450 μmol/L and eCO2 of 540 and 1200 μmol/L	Fructose (↑), glucose (↑), total soluble sugar (↑), total antioxidant capacity (↑), total phenols (↑), total flavonoids, ascorbic acid (↑) and Ca (↑) in the edible part of vegetables, protein (↓), nitrate (↓), Mg (↓), Fe (↓) and Zn (↓), total chlorophyll (-), carotenoids (-), lycopene (-), anthocyanins (-), P (-), K (-), S (-), Cu (-) and Mn (-)	[106]
Trifolium pretense (legume) and Agrostis capillaris (grass)	aCO2 of 400 μmol/mol and 700 μmol/mol and under drought with varying soil water content up to 15%	Leaf water potential (↓), root shoot ratio (↑) and leaf water area (↓)	[41]
Caragana microphylla Lam (sub-shrub legume species)	aCO2 of 380 μmol/mol and eCO2 of 760 μmol/mol + two nitrogen levels (0 and 17.5 g N/m/year)	Net photosynthesis (↑), above ground growth (↑), root biomass (-), root shoot ratio (-), symbiotic nitrogenase activity (-) and leaf N content (-)	[107]