Effects of two plant growth retardants on the diurnal variation of photosynthetic fluorescence in main branch walnut

QIN Jiang-nan;GUO Yong-cui;WANG Bo;SUN Hao-yang;ZHANG Rui;College of Plant Science,Tarim University;Xinjiang Production & Construction Crops Key Laboratory of Protection and Utilization of Biological Resources in Tarim Basin,Tarim University;College of Life Sciences,Tarim University;

QIN Jiang-nan%GUO Yong-cui%WANG Bo%SUN Hao-yang%ZHANG Rui%College of Plant Science,Tarim University%Xinjiang Production & Construction Crops Key Laboratory of Protection and Utilization of Biological Resources in Tarim Basin,Tarim University%College of Life Sciences,Tarim University

trunk-shaped walnut;;paclobutrazol(PP333);;mepiquat chloride(DPC);;photosynthetic characteristics;;photosynthetic fluorescence

【Objective】The purpose of this experiment was to screen out the types and optimum concentrations of plant growth retardants that could significantly improve the photosynthetic fluorescence efficiency of trunk-shaped walnuts,and provide reference for high-yield cultivation of walnut in Xinjiang.【Method】A 6-year-old trunk-shaped new Wen 185 walnut was used as the test material,and four concentrations of paclobutrazol(PP333)(500,1000,2000 and 3000mg/L)and mepiquat chloride(DPC)(200,300,400 and 500 mg/L)were set.The seedlings were sprayed twice on April 10 and May 28,2017.The difference in photosynthetic fluorescence of walnut leaves was compared during the oil conversion period(July 25).【Result】The results showed that the net photosynthetic rate(Pn),transpiration rate(Tr)and stomatal conductance(Gs)showed a bimodal curve under the various concentrations of PP333 and DPC.The maximum value of Pnwas12.50 μmol/(m2·s)treated with 1000 mg/L DPC,the maximum value of Trwas 6.93 mmol/(m2·s)under 200 mg/L PP333,the maximum Gswas 0.217 mol/(m2·s)treated by 1000 mg/L DPC.Walnut leaf initial fluorescence(Fo),the largest fluorescence(Fm),optical system II(PSII)total photochemical quantum yield(Yield)and PSII photochemical efficiency(Fv/Fm)presented down-up change under all concentrations.The diurnal change of PSII non-photochemical quenching coefficient(qN)presented a single peak curve,and its peak value appeared at 14:00 in control,the maximum in the treatments was 0.5368 under 400 mg/L DPC.PSII non-circulating photosynthetic electron transfer rate(ETR)presented dynamic change,and the maximum value was 224.15 under 500 mg/L DPC treatment.By analyzing the dereference between the two retardants groups,it was learned that under PP333,Pn,Gsand Trof walnut leaves were all extremely different from CK3(P<0.01),but all the photosynthetic parameters under DPC treatment were not significantly different from CK3(P>0.05).Foin PP333 treatment was significantly higher than CK3(P<0.05,the same below),and qN in DPC treatment was significantly higher than CK3.【Conclusion】The trunk-shape walnut can improve the absorption and utilization of light energy in walnut leaves under the treatment of 1000 mg/L PP333.