| Platycodon grandiflorum(Jacq.)A.DC is a perennial herb,and it is used as medicine with its dried roots.This paper focuses on the waterlogging stress characteristics,agronomic traits of Platycodon grandiflorum root growth regularity,photosynthetic characteristics and physiological response differences,theresults will guide the field cultivation of Platycodon grandiflorum,meanwhile,it also lays the theoretical foundation for the breeding of resistant varieties of wet stess type of Platycodon grandiflorum.The rapid growth period of main agronomic indexes of Platycodon grandiflorum was concentrated from May to June,which is in the jointing stage,while the number of index branches increased in the jointing stage and flowering stage.In different stages,the change trend of growth index of Platycodon grandiflorum aboveground and underground parts of indicators are not the same: the aboveground part of agronomic indexhas stabilized in flowering stage,the index of underground part continued to grow until the whole growth period end.Under the condition of waterlogging stress,some indexes of the aboveground part of Platycodon grandiflorum showed accelerated growth,while most of the underground roots were in the state of limited growth.The dry matter quantity of aboveground part and underground dry matter quantity of Platycodon grandiflorum were all decreased under the condition of wet treatment,which indicated that the waterlogging stress inhibited the accumulation of organic matter.Durning the four stages of Platycodon grandiflorum under waterlogging stress,chlorophyll a,chlorophyll b,total chlorophyll and net photosynthetic rate index decreased,and waterlogging later appeared chlorosis of Platycodon leaf color,which showed that waterlogging inhibited photosynthesis and leads to degradation of Platycodon grandiflorum,photosynthetic pigment.The stomatal conductance,intercellular CO2 concentration,transpiration rate and water utilization index showed a rising state,Which indicated that the Platycodon grandiflorum trys to ease the damage of the water wet environment by adjusting the Platycodon stomatal conductance,transpiration rate.Under waterlogging stress,the changes of physiological indexes in leaves of Platycodon grandiflorum were significantly different in the four growth stages: SOD showed a trend of increasing firstly and then decreasing in the growth stages,and the similarity was stronger.However,the changes of plasma membrane permeability,proline MDA and CAT content in different growth stages were more chaotic,which need further study.In addition,the total saponin content in roots was lower than that of the control group under the waterlogging stress condition in four growth stages,which indicated that the wet injury could inhibit the accumulation of saponins.We use factor analysis and membership function evaluation method to evaluate the resistance of Platycodon grandiflorum to waterlogging stress.In terms of growth index,the four growth period,fruit stage > seedling stage >flowering stage > jointing stage.In terms of physiological indicators,jointing stage > fruit stage > flowering stage> seedling stage.According to the physiological indexes: Fruit stage>seedling stage > flowering stage>jointing stage.It can be seen that at the jointing stage,the treatment of wet damage had the greatest effect on the growth index of Platycodon grandiflorum,and the wet treatment had a more significant effect on the photosynthesis of Platycodon grandiflorum at seedling stage.The comprehensive index of the wet damage response value showed that the resistance of waterlogging is weak in vegetative growth stage and reproductive growth exuberant flowering of Platycodon grandiflorum,and this stage is in the humid and rainy season,We need to be ready to prevent waterlogging in this period. |
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