Effects of photoperiod on leaf nutrition and photosynthetic physiology of Magnolia wufengensis 'Jiaohong 1'
[Objective]To provide reference for the cultivation of Magnolia wufengensis.[Method]Taking 2-year-old large container seedlings of M.wufengensis'Jiaohong 1'as the research object,six photoperiods were set by artificially regulating LED light source,respectively 8 h(light period)/16 h(dark period),10 h/14 h,12 h/12 h,14 h/10 h,16 h/8 h and natural light(CK).After a certain time of treatment,the growth of seedling height and ground diameter,leaf nutrient content,leaf protective enzyme activity,leaf photosynthetic pigment content,photosynthetic gas exchange parameters and chlorophyll fluorescence parameters were determined.[Result]The growth of seedling height and ground diameter under the treatment of 14 h/10 h was significantly higher than that of other treatments,and the growth of seedling height and ground diameter under the treatment of 8 h/16 h was significantly lower than that of other treatments.The content of photosynthetic pigment in leaves was significantly increased under 12 h/12 h and 14 h/10 h treatments,and significantly decreased under 8 h/16 h and 16 h/8 h treatments.In general,the net photosynthetic rate,stomatal conductance,transpiration rate and intercellular CO2 concentration of seedling leaves were the lowest under 8 h/16 h treatment,the highest under 14 h/10 h treatment,and the parameters were decreased under 16 h/8 h treatment.There were no significant differences in maximum fluorescence(Fm),initial fluorescence(Fo),photochemical quenching coefficient(CPQ)and non-photochemical quenching coefficient(CNPQ)between different photoperiod treatments and CK treatment.The values of relative electron transfer rate(ETR),PSII maximum light energy conversion efficiency(Fv/Fm),PSII potential photochemical activity(Fv/Fo)and PSII actual photochemical efficiency(ΦPSⅡ)under 14 h/10 h treatment were the highest and significantly higher than those under CK treatment,which were 26.33,0.77,3.45 and 0.74,respectively.[Conclusion]Photoperiod can affect the seedling height and diameter growth,leaf nutrient content,leaf protective enzyme activity,leaf photosynthetic pigment content,photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of M.wufengensis'Jiaohong 1'seedlings.Appropriately extending the light time in the photoperiod is conducive to improving the quality of M.wufengensis'Jiaohong 1'seedlings.The photoperiod of 14 h/10 h is the most suitable light condition for its growth.
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