Different Structures in Humic Substances Lead to Impaired Germination but Increased Protection against Saline Stress in Corn
2019
Pinos, N. Q. | Berbara, R. L. L. | Tavares, O. C. H. | García, A. C.
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 (HSᴬⁿᵈ), Histosol -Brazil (HSᴴⁱˢᵗ) and vermicompost (HSⱽᶜ) 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 HSᴬⁿᵈ are predominantly more aromatic and low polarity. The HSᴴⁱˢᵗ and HSⱽᶜ were less aromatic and had higher polarities. None of the tested HS stimulated corn seed germination and HSᴬⁿᵈ 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.
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