Effects of Exogenous Melatonin on Growth and Chlorophyll Fluorescence Characteristics of Chrysanthemum Seedlings under Drought Stress
With the seedlings of chrysanthemum'Xuanqiu Ninghong'as materials,and using 20% PEG solution to simulate drought stress,the effects of foliar spraying of different concentrations(50,100,150,200 μmol/L)melatonin(MT)on the biomass,root morphology and chlorophyll fluorescence parameters of leaves under drought stress were studied,in order to explore the alleviating effects of exogenous MT on light inhibition of drought stress to chrysanthemum seedlings.The results showed that the aboveground and underground bio-mass and total biomass of chrysanthemum seedlings under drought stress(T1 treatment)were significantly re-duced by 49.1% ,36.4% and 46.6% respectively compared with the control(CK),while those increased by 52.4% ,26.9% and 34.9% under T3 treatment(100 μmol/L MT+PEG)compared with T1 treatment,respec-tively.Moreover,when the concentration of MT was 100 μmol/L,the root activity and average diameter of roots increased to the highest,and the number of root tips decreased to the lowest.Compared with CK,exoge-nous application of different concentrations of MT significantly reduced the qP,NPQ,Fv/Fo,Fv/Fm and ETR of leaves,so maintained higher openness of PSⅡreaction center and improved the light energy utilization efficiency.In conclusion,spraying 100 μmol/L MT could effectively improve the chlorophyll fluorescence pa-rameters and photosynthetic performance of the leaves,and reduce the harm to the growth of chrysanthemum seedlings caused by drought stress.
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