不同根型苜蓿品种光合及叶绿素荧光对钾胁迫的响应OA

[Objective]To investigate the responses of alfalfa photosynthesis and chlorophyll fluorescence to low-potassium stress in different root-types.[Method]Three alfalfa varieties-creeping-rooted Medicago varia cv.Gong-nong No.4(GN),tap-rooted Medicago sativa cv.Longdong(LD)and rhizomatous-rooted Medicago sativa cv.Qin-gshui(QS)was used as the research object.Nutrient solution sand culture method was adopted.Three K levels were established:Normal potassium(CK,5 mmol/L KNO3),Moderate potassium deficiency(M,1 mmol/L KNO3),and Severe potassium deficiency(S,0.1 mmol/L KNO3).The effects of low-potassium stress on the morphological,photosynthetic,and chlorophyll fluorescence characteristics of alfalfa seedlings were analyzed.[Result]Under low-K stress,the plant height,leaf length,leaf width,leaf area,K⁺ content,chlorophyll a,chlorophyll b,carotenoids,chlo-roplast pigments,transpiration rate,photosynthetic rate,stomatal conductance,stomatal limitation,PSII potential pho-tochemical activity,PSII maximum photochemistry efficiency,photochemical quenching,photochemical quantum yield and electron transport rate of alfalfa with different root types all showed a decreasing trend.However,the inter-cellular CO2 concentration,water use efficiency,and non-photochemical quenching coefficient of alfalfa with each root type showed an increasing trend.Under S treatment,the chlorophyll a,chloroplast pigment,PSII potential photo-chemical activity,PSII maximum photochemistry efficiency,electron transfer rate,intercellular CO2 concentration,and water use efficiency of LD were higher than those of QS and GN.[Conclusion]Tap-rooted alfalfa exhibits greater adaptive capacity and tolerance to low-potassium stress than creeping-rooted and rhizomatous-rooted al-falfa.