Skip to main content

Table 1 Common mechanisms related to symptom relief of different types of abiotic stress (salinity, drought and heavy metal toxicity) by humic substances applied directly to plants or soils

From: Plant chemical priming by humic acids

Salinity

Osmoprotection/osmotic adjustment

Antioxidant activity

Ionic balance

Water efficiency use

References

Proline; sugars, phenols

–

✔

–

[15]

Proline, sugars,

CAT, SOD; ascorbic acids

✔

✔

[16]

Soluble protein

CAT, POX

✔

–

[17]

Soluble sugars, proline

CAT, SOD, GPOX; ascorbic acid, glut, TOC

✔

 

[18]

Soluble sugars

 

✔

–

[19]

Pigments

Ascorbic acid, phenols, anthocyanins

✔

✔ RWC

[20]

Proline

SOD, CAT, POX

–

–

[21]

–

–

✔

 

[22]

Pigments

–

✔

 

[23]

MDA, proline, H2O2

SOD, POD, CAT

✔

✔

[24]

–

–

✔

 

[25]

MDA. H2O2

SOD, APX, GST

  

[26]

Proline, free sugars

 

✔

✔

[27]

Heavy metal stress

Stress marker

Antioxidant activity

Uptake

Toxicity

References

Proline

CAT, SOD, POX

–

Fe

[28]

CAT, SOD, POX

–

Pb

[29]

SOD, CAT

+

Cd

[30]

SOD, POX

–

Cd

[31]

Protective DNA activity

  

Mn

[32]

 

+ or − according HA concentration

Cd

[33]

Decrease on H2O2 production and lipid peroxidation

 

–

Pb

[34]

Proline. MAD

SOD, CAT, GPOX, GST

 

Cu, Cd

[35]

 

–

Pb, Cd

[36]

Sugars, soluble proteins RWC

 

–

Cd

[37]

 

Decrease

Cd

[38]

Drought

Osmoprotection/osmotic adjustment

Antioxidant activity

Water efficiency use

References

–

–

Improve net photosynthesis

[39]

Changes in metabolic profile

CAT, POX and SOD

RWC

[40]

Proline, vitamin C

CAT, POX

RWC and (WEU)

[41]

Decrease of MDA; proline

Enhancement of CAT, POX, APX

 

[42]

MDA

Enzymatic: POX; decrease of H2O2 content

Enhance of aquaporins gene expression (TIPS)

[43]

Proline,

Enzymatic: POX; decrease of H2O2 content

 

[44]

  1. CAT: catalase activity; SOD: superoxide dismutase activity; POX: peroxidases; APX: H2O2: hydrogen peroxide concentration; RWC: relative water content; WUE: water use efficiency; GPOX: GST: MAD: malondialdehyde heavy metals: Cu (copper) Cd (cadmium): Fe (iron): Pb: Mn