NanoTiO2, Quantum dot-Graphene Oxide, and CeO2 Foliar Prescription Meliorates Growth and Some Physiological Traits of Gazania (Gazania splendens L.) Under Salinity

The production and maintenance of ornamental plants are closely related to the high consumption of fresh water. Today, due to the limited water resources, we have to water plants with salt water sources. To evaluate the effects of foliar application of nano TiO2, CeO2, and quantum dot-graphene oxide (zero and 1.5 mg/L) and NaCl salinity stress (0, 75, 150 mM) on Gazania splendens L.; a factorial experiment was conducted based on completely randomized design. The results revealed that plant dry weight, flower number, proline and flavonoids content, antioxidant enzymes activity, MDA, H2O2, Na, N, and P content were influenced by the interaction effects of experimental treatments. The highest leaf dry weight, flower number, and N content were recorded at no-salinity × quantum dot-graphene oxide. The highest data for Na content, ion leakage (56.6%), H2O2 (246 nmol/mg FW), malondialdehyde (37 nmol/mg FW), and proline (1.1nmol/mg FW) content were recorded at NaCl150 mM × no-foliar spray. 150 mM salinity stress × quantum dot-graphene oxide increased catalase activity (8.9 micro;mol/g FW) in the plant. Superoxide dismutase and ascorbate peroxidase activity were influenced by NaCl150 mM × quantum dot-graphene oxide and TiO2 foliar spray. Chlorophyll index, total phenolics, and K/Na ratio were responded to the simple effects of salinity and foliar application. The top ratio of K/Na and chlorophyll index was recorded at quantum dot-graphene oxide foliar spray. 75 and 150 mM salinity improved phenolics content in plants. Foliar spray with all nanoparticles increased phenolics content. The overall results showed that salinity had adverse effects on the growth and physiological characteristics of Gazania splendens. Foliar treatments under 150 mM salinity stress; promisingly influenced the antioxidant enzymes activity and root dry weight of plants. All in all, Gazania splendens can tolerate up to 75 mM NaCl salinity stress without a remarkable decline in growth and physiological attributes. /p