Table 1.
Effects of metal stress on phytohormone pathways.
| Hormone | Effect | Plant |
|---|---|---|
| Auxin | Cu inhibits meristematic cell division by decreasing PIN1 expression [56,57] | A. thaliana |
| Al inhibits root elongation via PIN2 and AUX1 [58] | ||
| Cd altered AUX1 and PIN expression; pin2-1 mutant fails to show Cd-induced increase in LR density [59] | ||
| Cytokinins | Increased cytokinin content in inhibited primary root during Cu stress [56] | A. thaliana |
| Cd induced increased cytokinin content via CKX5 [60,78] | A. thaliana | |
| Cd decreased cytokinin content [80] | wheat, soybean | |
| Restore Cd-induced inhibition on photosynthesis [79] | Chlorella vulgaris | |
| Gibberellins | Protect by diminishing Cd induced changes [92,93] | A. thaliana |
| Abscisic acid | Reduces Cd translocation by decreasing transpiration [124,125] | O. sativa |
| Initiate phytochelatin production [126,127] | Potato | |
| Ethylene | Cd upregulates ethylene responsive genes, via ACS2 and ACS6 [146] | A. thaliana |
| Reverse Zn-mediated Inhibition of photosynthesis [149] | ||
| Jasmonic acids | Elevated JA levels induce accumulation of phytochelatins, glutathione, carotenoids to enhance tolerance to low Cu and Cd [93,123,150] | A. thaliana |
| Brassinosteroids | Reduce toxic effects of Cd on phytochemical processes [200,201,202] | Brassica napus, Lycopersicon esculentum |
| Hypersensitivity to Cd [199] | A. thaliana | |
| Salicylic acid | Improves Cd tolerance by increasing antioxidative enzymes and decreasing H2O2 accumulation [213] | Phaseolus aureus, Vicia sativa |
| Reduces Cd uptake and enhance antioxidative activities [214] | Cannabis sativa | |
| Cd stress induced SA accumulation [215,216,217] | Pea, maize, A. thaliana |