Interactive effect of colloidal solution of zinc oxide nanoparticles biosynthesized using Ocimum gratissimum and Vernonia amygdalina leaf extracts on the growth of Amaranthus cruentus seeds

Abstract

Nanofertilizers may be a possible replacement for organic fertilizers because they can get to targeted sites in a plant and either enhance or thwart its growth depending on the toxicity level of the used nanoparticles. Zinc oxide nanoparticles are said to be a good source of nutrients for crop production and using these nanoparticles as bio fertilizers, could help to reduce the chemical residue in the grown vegetables which may sometimes be consumed raw or at an immature stage. Zinc oxide nanoparticles used in this work were biosynthesized using Ocimum gratissimum and Vernonia amygdalina leaf extracts. They were characterized using optical spectroscopy and electron microscopy and found to be of sizes ranging from 11 to 99 nm with some agglomeration. Colloidal solutions of these nanoparticles of concentrations 10, 100 and 500 mgl-1 were used as nanofertilizer for growing black-seeded and pale-seeded Amaranthus cruentus. Percent emergence was best at 69% for the pale seeded variety to which 100 mgl-1 Og-ZnO (pH 8) nanoparticles was applied and worst at 29% for the black seeded variety treated with 10 mgl-1 Og-ZnO (pH 12) nanoparticles. Best emergence index value of 2.28 was observed for the black seeded variety on the application of pH 8, 100 mgl-1 Og-ZnO nanoparticles. The pale seeded variety to which pH 12, 10 mgl-1 of Va-ZnO nanoparticles was applied gave the best emergence rate index results. The study showed that pH and concentration of nanoparticles can affect the seedling characteristics of A. cruentus seeds. Key words: Nanofertilizer, percent emergence, emergence index, emergence rate index, seedling characteristics, electron microscopy, optical spectroscopy.