Different Structures in Humic Substances Lead to Impaired Germination but Increased Protection against Saline Stress in Corn

• Published in: Communications in Soil Science and Plant Analysis Vol. 50; no. 17; pp. 2209 - 2225
• Main Authors: Pinos, N. Q., Berbara, R. L. L., Tavares, O. C. H., García, A. C.
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 25-09-2019; Taylor & Francis Ltd
• Subjects: abiotic stress; Aromatic compounds; Biological activity; Composting; Corn; Design of experiments; Experimental design; Germination; Humic acids; Humic substances; Humified organic matter; lability; NMR; Nuclear magnetic resonance; Plant growth; Plant protection; Polarity; recalcitrance; Seed germination; Soil; Soil contamination; Structures; Vermicomposting; Worms
• ISSN: 0010-3624; 1532-2416; 1532-4133
• DOI: 10.1080/00103624.2019.1659294

The effects of humic substances (HS) on plants are related to humic structure. The present study aimed to characterize HS different origins and to evaluate the effects on germination and protective effects against salt stress in corn. HS were extracted from an Andosol -Ecuador (HS
And
), Histosol -Brazil (HS
Hist
) and vermicompost (HS
Vc
) and characterized by
13
C-NMR CP/MAS combined to chemometric analyzes. Germination indexes and metabolic parameters were used to evaluate the effects of HS on corn plants. Two types of experiments were performed, both with a completely randomized experimental design and twenty-five replicates per treatment. The results show that HS
And
are predominantly more aromatic and low polarity. The HS
Hist
and HS
Vc
were less aromatic and had higher polarities. None of the tested HS stimulated corn seed germination and HS
And
had more pronounced negative effects. Protective effects of HS were related to different structures. Labile structures were related to plant growth and more aromatic structures affected the plant's pigment production. The humic structural balance increases HS bioactivity and protective effects more than a specific type of structure. The present results are important for agriculture because maintaining HS with adequate structural quality in soils may protect plants from eventual periods of high salinity.