Study On Photosynthetic Characteristics Of Phyllostachys Edulis Stems During Rapid Growth Period

In order to reveal the photosynthetic pigmentcontents,chlorophyll fluorescence characteristics and reflectance spectra of different internodes in the rapid growth period of Phyllostachys edulis.The shoots and stems were used as materials in this study,we measured the photosynthetic pigment contents,chlorophyll fluorescence parameters and reflectance spectrum parameters of different internodes of P.edulis stems.The main conclusions are as follows:1.When P.edulis shoots grew to 6 m,the contents of chlorophyll a,chlorophyll b and carotenoid decreased in the green tissue with the increased of internodes（P<0.05）.The changes of the 1-7internodes were relatively small,and the 10-22 internodes were large.The chlorophyll a/b ratio showed an increasing trend as a whole.2.With the increased of internodes,the spectral reflectivities were obviously different.The whole reflectivity of visible light region was increased.There were two absorption troughs at wavelength490nm and 680nm,and a peak at 560nm.The reflectivities of near infrared region fluctuated with the increased of internodes.The“blue shift”appears in the red edge position,and the area of the red edge decreased significantly（P<0.05）.The blue edge position and the yellow edge position of different internodes had no changed significantly.The chlorophyll spectral index（SR680,PSSRa,PSSRb,NDVI,rNDVI,mND,PSNDa,PSNDb）and the carotenoid spectral index（RARSc,PSSRc,CRI,Mcri,PSRI）were decreased significantly（P<0.05）.3.With the increased of internodes,minimum fluorescence（F₀）was increased and maximum fluorescence（F_P）showed a decreasing trend as a whole.The unit area captured light energy（TRo/CSo）,probability of trapping excitons to other electron receptors downstream of Q_A^-（ψ_o）,PSⅡreaction center absorbed light energy for electron transfer quantum yield(φ_Eo),maximum photochemical efficiency(φ_Po),number of reaction centerper unit area（RC/CSo）and photosynthetic index based on absorbing light energy(PI_ABS)were decreased significantly（P<0.05）.Light energy absorbed by unit reaction center（ABS/CSo）,quantum ratio for heat dissipation（φDo）and energy dissipation per unit reaction center（DIo/RC）were increased significantly（P<0.05）.In conclusion,the contents of photosynthetic pigment,chlorophyll fluorescence and reflectance spectra were obviously different between different internodes of stems in the rapid growth period of P.edulis.The structure of PSⅡin the internodes of middle and lower parts had been basically developed and perfected.The contents of photosynthetic pigment were higher,the chlorophyll fluorescence and spectral reflectivities were lower,efficiency of absorption and conversion of light energy was higher and the photosynthetic ability was stronger,the energy dissipation was less,so the middle and lower stems grew faster and the upper internodes grew slower.