Research On Photosynthetic Characteristics In Camellia Japonica Growing At The Understory

Camellia japonica L. is one of the most famous ten flowers in china and it possess great ornamentalvalue and medicinal value.Camellia japonica L.has a significant effect on the ecological environment aswell. Research the photosynthetic characteristics of Camellia japonica at the open forest and theunderstory with the seasonal changes can provide theory basis for cultivating management andlandscape application etc. of the camellia japonica.This topic was that gas exchangeparameters,chlorophyll fluorescence parameters,and the content of nutrient elements etc.of the twotypes of Camellia japonica measured with LI-6400portable photosynthesis system in April, August andDecember in the selected sample area. The results showed that:1) Gas exchange parameters net photosynthetic rate (Pn) and stomatal conductance(Gs) ofCamellia japonica at the understory have not significantly change,but the apparent quantum yield (AQY)was significantly increased from April to August;Yet the net photosynthetic rate(Pn), stomatalconductance(Gs) and apparent quantum yield(AQY) of Camellia japonica at the open forest weremarkedly reduced; In addition, the intercellular CO2concentration(Ci) and transpiration rate(Tr) of thetwo types of Camellia japonica L.were significantly increased;The gas exchange parameters of the twotypes of Camellia japonica were significantly reduced from August to December.2) The PSII maximum photochemical efficiency(Fv/Fm),PSII effective photochemical quantumyield(F ’v/F’ m), PSII actual photochemical efficiency(φPSⅡ) and photochemical quenching(qP) ofCamellia japonica at the open forest were significantly decline from April to August,while itsnon-photochemical quenching(NPQ) was rise significantly.But these chlorophyll fluorescenceparameters of Camellia japonica at the understory did not change significantly.3) The relative electron transfer rate(ETR),the electron flow used in carbon assimilation and theelectron flow in light respiration of two types of Camellia japonica were decreased from April toDecember, Camellia japonica at the open forest significantly reduced while Camellia japonica at theunderstory have not.4) The mesophyll conductance(gm) and Chloroplast CO2concentration (Cc) were increased withdifferent levels from April to August, while the gm and Ccof the Camellia japonica L. at the open forestwere significantly reduced; 5)The maximum carboxylation rate (Vmax) and the maximum electron transfer rate (Jmax) of the twotypes of Camellia japonica were decreased from April to December, Camellia japonica at the open forestsignificantly reduced while Camellia japonica at the understory have not..6) The nitrogen and phosphorus content of Camellia japonica at the understory had no changewhile the content of potassium was increased significantly from April to August,Nitrogen,phosphorusand potassium content of two kinds of Camellia japonica were significantly decreased from August toDecember.All above,we could see that the photosynthesis efficiency of Camellia japonica at the understorywas lower than the control group;High temperature in summer made the photosynthesis rate of Camelliajaponica at the open forest significantly decreased, while the photo-inhibition of Camellia japonica atthe understory was small and the shading could relieve the high temperature to a certain extent;Non-photochemical quenching rising, transpiration rate increasing and photorespiration decreasing wereprotective mechanism of plant resistance to high temperature.