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

ABSTRACT

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 ¹³C-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.

KEYWORDS:

• Humified organic matter
• abiotic stress
• recalcitrance
• lability

Acknowledgments

A.C.G. (sisFaperj: 2012028010), E.Z, O.C.H.T, R.L.L.B thanks Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) for support and grant “cientista do nosso estado” and “jovem cientista do nosso estado”. N.R.Q.P thank to Secretararia de Educación Superior Ciencia Tecnologia e Innovación (SENESCYT) and Instituto de Fomento al Talento Humano (IFTH) of Equador for support and grant. Thank the National Counsel of Technological (CNPq) for funding through the project PDJ program (168782/2017-0). This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001”

Disclosure statement

The author declares no conflict of interest.

Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico [Bolsa de Pesquisa Nível B];Coordenação de Aperfeiçoamento de Pessoal de Nível Superior [Finance Code 001];Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro [sisFaperj: 2012028010];Secretaría de Educación Superior, Ciencia, Tecnología e Innovación [N.Q.P].