The seed stimulant effect of nano iron pyrite is compromised by nano cerium oxide: regulation by the trace ionic species generated in the aqueous suspension of iron pyrite

Abstract

A brief seed pretreatment of 12 hours, in an aqueous suspension of synthesized nano iron pyrite (FeS₂), significantly increases the yield of spinach and other crops. The effector mechanism is not clear. An aqueous suspension of FeS₂, produces very trace amounts of H₂O₂, Fe₂O₃, FeS, FeSO₄, Fe(SO₄)₃, SO₂, S and H⁺ ionic species. Thus for 12 hours, seeds are exposed to this complex aqueous suspension. Among these trace species, H₂O₂ and Fe₂O₃ are known seed stimulants and plant growth promoters respectively. In this work, an attempt has been made to quench one of these trace compounds generated in the aqueous suspension of FeS₂, viz., H₂O₂; and the long-term effect on the mature plant was monitored. To test this, along with FeS₂, an agriculturally relevant inorganic peroxide scavenger viz., nano cerium oxide (CeO₂) was introduced into this system. Four seed pretreatment regimens were followed for the spinach viz., (i) control (water), (ii) FeS₂ + water, (iii) CeO₂ + water, (iv) FeS₂ + CeO₂ + water; and growth was monitored for the next 80 days. It was found that, at maturity, CeO₂ and FeS₂ + CeO₂, resulted in significantly smaller leaves, as compared to the control and FeS₂; furthermore, FeS₂ resulted in leaves with increased chlorophyll and carbohydrate. Thus, the data indicates that by quenching the H₂O₂, the seed-stimulant effect of FeS₂ is compromised. So, while the FeS₂ + water suspension functions as a seed vigor enhancer, CeO₂ + water on the contrary, functions as a ‘seed vigor reducer’. It is noteworthy, that CeO₂ is used by Chinese farmers, as a micro-nutrient to increase crop production. Current data indicates that, it delays germination of seeds, whereas FeS₂ hastens germination. Thus such an approach could be used for hastening or delaying germination, manipulating weed population, seed storage in critical conditions, timing the life-cycle of a plant and developing more energy-efficient plants, especially in regions, where there is limited sunlight during significant parts of the year.