Table 1.
The effect of auxin application on rice during heavy metal stress.
| Trearment | Application | Conc. | Effect | References |
|---|---|---|---|---|
| Cd (30 mg kg−1 of soil) | Exogenous Se and L-TRP (auxin precursor) | 10−5 M | Enhanced growth and yield under Cd stress by stabilizing endogenous auxin levels and decreasing Cd translocation to rice grains | [21] |
| As | Exogenous IAA | 3.0 M | Reduced As-induced stress more efficiently when used in combination with selenium and improved chlorophyll content, proline, and cysteine; lowered protein content inhibition and DNA damage; reduced lipid peroxidation | [22] |
| - | Exogenous indole-3-butyric acid (IBA) | 1 µM | Increased synthesis of nitric oxide in lateral roots and heme oxygenase activity | [23] |
| Mercury (60 µM) | Exogenous nitroprusside (SNP or NO) | 200 µM | Induced auxin transport in roots and improved resistance to Hg-stress, decreased Hg uptake and transportation in roots and shoots, decreased auxin levels during iron deficiency. Antioxidant activity was not enhanced by SNP | [24] |
| Cd/As | Exogenous IAA or IBA | 100 mM | Mitigated alterations in root system caused by Cd stress by increasing nitric oxide content and lateral root production and AUX1 expression | [25] |
| Hexavalent chromium (300 µM) | OsMYB-R1 overexpressing lines | - | Rice plants showed higher auxin accumulation, overexpression of OsMYB-R1-induced antioxidative genes such as CAT, SOD, guaiacol peroxidase; and regulated salicylic acid signaling under Cr 300 µmol L−1 and other abiotic stresses | [26] |
| CdSO4 and Na2HAsO4 (100 µmol L−1) | IAA or IBA | 10 µM | Altered OsAUX1, OzYUCCA1, OsASA2 IAA-biosynthesis gene and OsYUCCA1 expression was downregulated under As and Cd toxicity, while OsASA2 expression was not influenced with or without Cd and As. 100 µmol L−1 CdSO4 and 100 µmol L−1 Na2HAsO4·7H2O | [25] |
| As | IAA | 2.0 μmol L−1 | Enhanced grain biomass, reduced As translocation, decreased the As concentration in rice grains | [27] |
| Cd | NAA | 1.0 and 10 μmol L−1 | Enhanced plant biomass, restricted seedling growth in both wild type and transgenic pmei12 lines | [20] |
| Vanadium (0–2 mM) | - | - | Five genes encoding auxin response transcription factors (OsIAA) as well as enhanced abscisic acid (ABA) and jasmonic acid (JA) expression in hormone signaling pathways. Upregulated ATP-dependent GSH-conjugated transport, ATP binding cassette (ABC) transporter, and markedly reduced the expression of divalent cation transporters, drug/metabolite transporter (DMT), and zinc/iron permease (ZIP) | [28] |