Table 4.
Effectiveness of exogenous CA on mediating HM stress tolerance.
| Plant Species | HM Stress | Treatments | Effects | Outcomes | References |
|---|---|---|---|---|---|
| Brassica napus | Cu (50 and 100 µM as CuSO4) | CA (2.5 mM) in nutrient solution |
Increased plant growth, biomass, Chl content, stomatal conductance, and water use efficiency. Enhanced POX, SOD, CAT, and APX activities. Reduced H2O2, MDA, and EL. | Minimized Cu toxicity and enhanced biomass production. | [56] |
| Brassica napus | Cd (10 and 50 µM as CdCl2) | CA (2.5 mM) in solution medium |
Enhanced plant growth and biomass, gas exchange activities, and antioxidant enzymes activity. Reduced oxidative stress by reducing H2O2 and MDA production and decreasing EL. | Mitigated Cd stress. | [16] |
| Solanum nigram | Cd (50 mg Cd2+ kg−1 dry soil) | CA (20 mmol kg−1 soil) applied in soil | Promoted plant growth, biomass, and antioxidative defense e.g., SOD and POX activity at initial stage. | Slightly reduced Cd stress. | [70] |
| Brassica juncea | Cd (0.6 mmol kg−1 soil as CdCl2) | CA (0.6 mmol kg−1 soil) applied in soil | Increased plant height, Chl a+b, carotenoid, anthocyanins, and flavonoids in leaves. Non-significant increment of the activities of SOD, POX, CAT, and GPX. Reduced MDA levels. | Alleviated Cd-induced toxicity. | [68] |
| Brassica juncea | Cd (0.6 mM) as CdCl2 | Soil treatment with CA (0 and 0.6 mM) |
Significantly increased Chl a+b, carotenoid, and polyphenols. Non-significant increase in flavonoids, anthocyanins and total carbohydrate content. Induced stomatal opening. Reduced ROS production. | Alleviated Cd stress. | [33] |
| Brassica napus | Cr (100 and 500 μM) | Irrigated with CA (2.5 and 5.0 mM) | Increased plant growth, biomass, Chl a, Chl b, Chl a+b, carotenoid, and soluble protein concentrations. Enhanced activities SOD, POX, CAT, and APX. Reduced MDA and EL. | Improved Cr stress tolerance. | [58] |
| Brassica juncea | Cd (0.5 mM Cd and 1.0 mM CdCl2) | CA (0.5 and 1.0 mM) in nutrient solution | Increased plant growth, leaf RWC, and Chl content. Enhanced activities of APX, MDHAR, DHAR, GR, GPX, SOD, and CAT. Reduced oxidative damage. | Enhanced Cd stress tolerance by regulating antioxidant defense. | [53] |
| Helianthus annuus (Sunflower) | Cr (5, 10 and 20 mg kg−1 dry weight) | CA treatment (2.5 and 5.0 mM) |
Increased plant growth and biomass, Chl, carotenoid, photosynthesis, gas exchange, and soluble proteins. Enhanced activities of antioxidant enzymes. Reduced production of ROS and MDA. | Improved Cr stress tolerance. | [59] |
| Juncus effusus | Mn (50, 100 and 500 μM as MnSO4) | CA (5 mM) in the nutrient solution |
Increased shoot length and root number. | Alleviated Mn toxicity and enhanced growth. | [71] |
| Germinating pea seeds | Cu (as 200 µM CuCl2) | Irrigated with CA (as 100 µM Na-citrate) |
Reduced oxidative stress. Decreased H2O2, MDA, carbonyl groups, lipid peroxidation, and protein oxidation. | Enhanced growth and reduced stress. | [67] |
| Zea mays (Maize) | Cd as CdCl2 (300 mg kg−1) | Irrigation with CA (0.25, 0.5, 1.0 and 2 g kg−1 soil) | Increased root and shoot length, biomass. Reduced bioaccumulation coefficient and translocation factor. Reduced Cd uptake. | CA proved inefficient for Cd phytoextraction, however, ameliorated the toxicity of Cd |
[63] |
| Brassica juncea | Cd (150 mg Cd2+ kg−1 soil) | CA (10 and 20 mmol kg−1 soil) | Increased shoot phenolic acids. Reduced ROS production. | Improved Cd stress tolerance. | [66] |
| Brassica napus | Pb as Pb(NO3)2 (50 and 100 μM) | CA (2.5 mM) in solution media |
Increased plant height, root length, leaf growth, fresh and dry weight, Chl content, SPAD values, Pn, E, Gs, and Pn/E. Enhanced SOD, POX, CAT, and APX activities. Prevented lipid membrane damage. Reduced MDA and H2O2 production. | Increased Pb stress tolerance. | [57] |
| Solanum lycopersicum | Pb (10 μM as Pb(NO3)2) and As (10 μM as Na2HAsO4) | CA (250 μM) in nutrient solution |
Increased Chl a and Chl b content. Decreased Pb accumulation, α-tocopherol content, and MDA levels. | Increased Pb and As tolerance. | [69] |
| Roots of Vicia faba | Pb (5 μM) as Pb(NO3)2 | CA (550 μM and 1000 μM) in nutrient culture | Non-significant effect on antioxidant enzyme activities (i.e., SOD, GPX, APX, and GR). | CA did not mitigate Pb toxicity | [73] |
| Sedum alfredii | Cd (100 µmol L−1 CdCl2) | CA (0, 10, 50, 100, 500 µmol L−1) in solution culture | Increased plant growth and biomass. | Improved Cd stress tolerance | [74] |
| Corchorus olitorius | Cd (20 mg L−1) as Cd(NO3)2. 4H2O |
5 mM CA in nutrient culture | Enhanced antioxidant enzyme activity. Decreased Cd2+ uptake and accumulation. | Improved Cd stress tolerance | [62] |
| Salix variegate | Cd (50 μmol L−1) as CdCl2·2. 5H2O |
CA (100 μmol L−1) in nutrient solution | Increased biomass, carotenoid, Chl a, Chl b and Chl a+b content. Increased net photosynthesis rate, stomatal conductance, chloroplast size and width. | Reduced stress and enhanced growth, biomass, and photosynthesis. | [55] |
| Brassica juncea | Ni as NiSO4 (0.003 mmol L−1) | CA (0.5, 1.0, and 5.0 mmol L−1) in nutrient solution | Reduced Ni uptake but had no effect on Ni translocation. | Reduce stress by reducing Ni uptake. | [65] |
| Brassica juncea | Cd (0.6 mM) | Foliar spray of CA (0.6 mM) | Increased plant growth. Increased antioxidant activity. Reduced ROS. |
Enhanced growth and efficacy of photosynthetic machinery | [61] |
| Helianthus annuus (Sunflower) | Cr (5, 10, and 20 mg kg−1) | Irrigation with CA (2.5 and 5 mM) | Increased plant growth, Chl, carotenoid, Pn, E, Gs, and water use efficiency. | Increased tolerance to Cr stress. | [40] |
| Larix olgensis | 100 mg kg−1 Pb from Pb(NO3)2 | Root irrigation and foliar spraying of CA (0.2, 1.0, 5.0, and 10.0 mmol L−1) | Increased plant growth and biomass, proline, total Chl, and carotenoid content. Enhanced SOD and POX activities. Reduced Pb content and MDA levels. | Improved tolerance to Pb stress | [54] |
| Oryza sativa (Rice) | Cd as CdCl2 (25.0 µM) | CA (50.0 µM) in nutrient solution | Increased GSH, Chl, carotenoid, and anthocyanin contents. Decreased Cd content in leaves. | Enhanced Cd tolerance and promoted higher biomass production | [60] |
| Triticum aestivum (Wheat) | 20 µM Cd (added as CdCl2) | Irrigation with CA (10, 50, 100, and 500 µM) | Increased index of tolerance, root and shoot biomass. Decreased Cd uptake, MDA levels, and PCs-SH production in roots. | Reduced bioavailability of Cd. | [64] |
| Medicago sativa (Alfalfa) | 100 µM Al in nutrient solution | Foliar spraying with 100 µM of CA | Increased growth. Reduced lipid peroxidation. | Alleviated Al toxicity through roots Al detoxification | [75] |
| Typha latifolia | Pb and Hg (1, 2.5 and 5 mM) | CA (5 mM) in nutrient medium |
Increased fresh and dry biomass of root, stem, and leaf. Increased Chl a, Chl b, Chl a+b, carotenoid, soluble protein contents, and SPAD values. Decreased ROS, MDA, and EL. Enhanced the activities of SOD, POX, APX, and CAT. | Improved stress tolerance with increased physiological parameters. | [72] |