ZnO Nanoparticle Biosynthesis and Its Effect on Phosphorous-Mobilizing Enzyme Secretion and Gum Contents in Clusterbean (Cyamopsis tetragonoloba L.)

Biological synthesis of ZnO nanoparticle is a new approach for environmentally benign protocol in context to green nanotechnology. In present investigation, ZnO nanoparticles were synthesized from ZnNO3 using extracellular secretions of Aspergillus fumigatus TFR-8 (NCBI GenBank Accession No. JQ675291) and effect of these biologically transformed ZnO nanoparticles was studied on clusterbean (Cyamopsis tetragonoloba L.) to enhance native phosphorous-mobilizing enzymes and nanoinduced gum production. Valid characterization techniques were employed for confirmation of size, shape, surface structure, crystalline nature, and elemental proportion. Results indicate that synthesized nanoparticle size ranging between 1.2 and 6.8 nm at least in one dimension with oblate spherical and hexagonal in structure. The samples contained 98 % atom of Zn element. The characterized ZnO nanoparticles were foliar sprayed at 10 ppm concentration on leaf of 14-day-old clusterbean plants. A significant improvement in plant biomass (27.1 %), shoot length (31.5 %), root length (66.3 %), root area (73.5 %), chlorophyll content (276.2 %), total soluble leaf protein (27.1 %), rhizospheric microbial population (11–14 %), acid phosphatase (73.5 %), alkaline phosphatase (48.7 %), and phytase (72.4 %) activity in clusterbean rhizosphere was observed over control in 6-week-old plants due to application of nanoZnO. The gum content in clusterbean seeds improved by 7.5 % after maturity which indicates ZnO in nano form may contribute more in industrial and medical applications besides agricultural sector. A possible hypothesis of mechanism for ZnO nanoparticle biosynthesis has also been made.