Effects of graphene oxide and zinc oxide nanoparticles on growth, chlorophyll, carotenoids, proline contents and diseases of carrot

Abstract

The effects of graphene oxide (GO) and zinc oxide (ZnO) nanoparticles (NPs) at two concentrations, i.e., 0.05 mg ml−1 and 0.10 mg ml−1 were observed on Pectobacterium carotovorum, Xanthomonas campestris pv. carotae, Meloidogyne javanica, Alternaria dauci and Fusarium solani on the growth of carrot (Daucus carota). Specific physiological variables studied include chlorophyll, carotenoid and proline contents. Inoculation of plants with P. carotovorum, X. campestris pv. carotae, M. javanica, A. dauci and F. solani reduced plant growth and chlorophyll and carotenoid contents but increased proline contents. Application of GO or ZnO NPs to plants with or without pathogens caused significant increases in plant growth, chlorophyll, carotenoid and proline contents. ZnO NPs were more effective than GO NPs in increasing plant growth, chlorophyll, carotenoid and proline contents. The 0.10 mg ml−1 concentration of both NPs was more effective in increasing plant growth, chlorophyll, carotenoid and proline contents than the 0.05 mg ml−1 concentration. Galling and multiplication of M. javanica was reduced by NPs application. ZnO NPs at concentration, 0.10 mg ml−1 caused highest reduction in galling and nematode multiplication and GO NPs at 0.05 mg ml−1 the least. Soft rot, bacterial leaf blight, leaf spot and root rot indices caused by P. carotovorum, X. campestris pv. carotae, A. dauci and F. solani respectively were 4. Disease indices were reduced to 2 when 0.05 and 0.10 mg ml−1 GO and 0.05 mg ml−1 ZnO were sprayed onto plants with test pathogens. Indices were highly reduced to 1 when 0.10 mg ml−1 ZnO was sprayed onto plants with test pathogens.