Influence Of Exogenous Nitric Oxide, Nano-TiO₂ And Lanthanum Rare Earth On The Senescence Of Flowering Shibataea Chinensis Nakai

The experiment was focused on photosynthesis effect of exogenous nitric oxide(100～400 mg/L), Nano-anatase TiO₂ (50～450mg/L) and lanthanum rare earth (50～450mg/L) on the senescence process of flowering Shibataea chinensis Nakai.The effects of exogenous materials on photosynthetic characters were as foll- ows:the photosynthetic gas exchange parameters showed that the net photosynthetic rate (Pn), stomata conductance (Gs), transpiration rate (Tr), intercellular CO₂ concentration (Ci) decreased increased, and stomatal limitation (Ls) increased gradually in normal senescence process. However, after treatment with the three exogenous materials, Pn, Gs, Tr and Ci increased first and then decreased, and Ls was the exact opposite. The chlorophyll fluorescence parameters revealed that, compared to the control group, the decreases of PSII maximal photochemical efficiency (Fv/Fm), PSII potential activity (Fv/F0), PSII effective photochemical efficiency (Fv'/Fm'), PSII actual photochemical efficiency (ΦPSâ…¡) and acyclic electron transfer rate (ETR) were significantly inhibited during the processes of senescence when the leaves were treated with different amounts of exogenous materials. But the effects and mechanisms were different. From the two parameters above, we found that the effect of exogenous nitric oxide and Nano-anatase TiO₂ were better than lanthanum rare earth.The effect of exogenous materials on the isolated leaves senescence were as follows:exogenous nitric oxide and lanthanum rare earth at appropriate concentra- tions effectively delayed the decrease of the content of soluble proteins (Pr), chlorophyll (Chl), ascorbic acid (ASA), reduced glutathione (GSH) and the bioactivity of superoxide dismutase (SOD), peroxydase (POD) and the PSII maximal photochemical efficiency (Fv/Fm), PSII potential activity (Fv/F0), also the extensive peroxidation of membrane liquid in senescence process. SDS-PAGE analysis of soluble proteins showed that proteins degradation, especially the relatively higher molecular weight proteins, was significantly slowed down when leaves were pretreated with S30 and L5. Two different proteins, with the molecular mass 100.9KD and 22.4KD respectively, were presumably related to senescence process of flowering Shibataea chinensis Nakai leaves. Ultrastructure with SEM exhibited the irregular shape of emesophyll cell, the broken of plasma membrane system and disorganized internal structure, which were improved by S30 and L5. The cells maintained complete structure.