Growth, Photosynthesis and Quality of Water Spinach (Ipomoea aquatica) as Influenced by Magnetic Nanoparticles (MNP) Application

Aims: To characterize the growth, carbon assimilation and quality of Ipomoea aquatica as influenced by magnetic nanoparticles (MNP) application as well as to determine the best rates of iron oxide nanoparticles that give high growth, carbon assimilation and quality of Ipomoea aquatica.

Study Design: Ipomoea aquatica plants were exposed to four different treatments of magnetic iron oxide nanoparticles (Fe3O4) (0, 50, 100 and 150 mg L-1). The experiment was conducted in a randomized complete block design (RCBD) with 3 replications. One unit of experiment consisted of 8 plants and there were 96 plants used in the experiment.

Place and Duration of Study: Department of Biology, Faculty of Science, Universiti Putra Malaysia, between March 2018 and July 2018.

Methodology: The growth parameters measured included: plant height, basal diameter, total leaf number, leaf temperature, total chlorophyll content and plant biomass. The carbon assimilation parameters were measured using IRGA (Infrared Gas Analyzer, LICOR 6400 XT Portable Photosynthesis System). i.e. transpiration rate (E), stomatal conductance and water use efficiency (WUE). The chlorophyll fluorescence were measured by using Pocket PEA that measured maximum efficiency of photosystem ii, (fv/fm), maximum quantum yield of phytochemical and non-photochemical process in photosystem II (fv/fo), minimal fluorescence (fo), performance index (PI) and Density of Reaction Centers Per PSII Antenna Chlorophyll (RC/ABS). Total phenolics and flavonoids contents in leaves were measured using Folin-Ciocalteu method.

Results: It was observed that plant height, shoot length, plant temperature, total biomass, and total chlorophyll content were significantly influenced (p≤0.05) by the different concentrations of magnetic nanoparticles. The net photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs), maximum efficiency of photosystem II (Fv/fm), maximum quantum yield of phytochemical and non-photochemical process in photosystem II (Fv/fo), performance index and the density of reaction centers per PSII antenna chlorophyll of Ipomoea aquatica were significantly reduced at higher concentration of magnetic nanoparticles. However, water use efficiency and minimal fluorescence value (Fo) of Ipomoea aquatica increased with increase of MNP concentration. In addition, the application of magnetic nanoparticles significantly influenced (P≤0.05) the total flavonoids and total phenolics content in water spinach. Both of these parameters were increased when higher concentration of magnetic nanoparticles was applied to Ipomoea aquatica. This study showed that MNP affected the growth, carbon assimilation and secondary metabolites production of Ipomoea aquatica.

Conclusion: In conclusion, the higher concentration of magnetic nanoparticles reduced the growth rate and carbon assimilation of water spinach and enhanced the production of secondary metabolites.