Effect of chitosan on physiology, photosynthesis and biomass of rice (Oryza sativa L.) under elevated ozone

This research aimed to study the effects of chitosan on physiology, photosynthesis and biomass of rice cultivar RD47 under elevated ozone. Rice samples were grown at indoor climate controlled chambers, allowing the inlet air to pass through charcoal filters. For combined effects of chitosan and ozone, rice was soaked and sprayed with chitosan 0.05% (W/V) under elevated ozone concentration at 40 ppb (Chi+EO 3 40) and 70 ppb (Chi+EO 3 70). Control groups (CF) with no additional ozone were also studied. Samples were analyzed weekly for tiller number per plants, leaf area, leaf chlorophyll, photosynthesis, shoot biomass, root biomass and total biomass. The results obviously showed that ozone at the concentration of both 40 and 70 ppb caused negative effects on rice physiology, photosynthesis and biomass. The 70 ppb concentration, particularly, caused sever damage. Whilst soaking and spraying with chitosan could significantly reduce the harmful effects of ozone compared with the control group. For the samples soaked and sprayed with chitosan under elevated ozone for 21 days, Chi+EO 3 40 and Chi+EO 3 70 significantly performed more photosynthesis and contained more leaf chlorophyll than EO 3 40 and EO 3 70, respectively (p 0.05). In addition, chitosan could reduce the ozone negative effects and increased higher physiology and photosynthesis rate. However, there was no significant difference in biomass compared with the control group. Even through, ozone has been gradually increasing which made plants at risk, chitosan treatment could significantly ameliorate the effect of ozone and serve as a plant growth promoter with no harmful to human being.