Physiological responses of different varieties of soybean to low phosphorus stress and comprehensive evaluation
[Objective]To investigate how seedlings of various soybean varieties reacted to low phosphorus stress and to offer a theoretical reference for selecting and breeding more low phosphorus tolerant soybeans.[Method]Thirteen soy-bean varieties Qiandou 11(Qd11),Shangdou 1013(Sd),Niumao soybean(Nm),Zhonghuang 13(Zh13),Qixing 1(Qx1),Huachun 6(Hc6),Zhonghuang 30(Zh30),Huaxia 3(Hx3),Aixuan(Ax),Huaxia 2(Hx2),Suiyangdou(Sy),Zhonghuang 301(Zh301),and Zhonghuang 61(Zh61)were used as test materials.Two phosphorus treatments were set up:0.5 mmol/L KH2PO4 for normal phosphorus supply and 0.02 mmol/L KH2PO4 for low phosphorus stress.The effects of low phosphorus stress on the growth morphology and physiological characteristics of soybean seedlings were in-vestigated through the sand cultivation test.The ability of different soybean varieties to tolerate low phosphorus was com-prehensively evaluated by the membership function method.[Result]While the root-shoot ratio and aboveground phospho-rus use efficiency tended to rise,soybean plant height,stem diameter,leaf area,aboveground dry weight,and phospho-rus content tended to decrease under low phosphorus stress.The SPAD values and fluorescence parameters of soybean leaves were also impacted by low phosphorus stress;there were primarily increasing trends in initial fluorescence(Fo)and decreasing trends in maximum fluorescence yield(Fm),variable fluorescence(Fv),potential PS II activity(Fv/Fo),and maximum photochemical efficiency of PSII(Fv/Fm).Additionally,low phosphorus stress led to a tendency of decrea-sing the malonaldehyde(MDA)content of soybean leaves,while superoxide dismutase(SOD)and peroxidase(POD)ac-tivities exhibited an increasing trend.The thirteen soybean varieties could be divided into three categories based on capac-ity comprehensive value(D)of the comprehensive evaluation of low phosphorus tolerance:low phosphorus tolerant type,intermediate type,and low phosphorus sensitive type.Low phosphorus tolerant varieties(Qx1,Sy and Hx2)dem-onstrated greater physiological regulation overall,higher aboveground phosphorus utilization efficiency,and the ability to maintain normal photosystem pathways by increasing the activity of antioxidant enzymes to reduce leaf damage;inter-mediate varieties(Ax,Zh30,Hc6 and Qd11)had lower leaf membrane damage but greater photosystem damage;low phosphorus sensitive soybean varieties(Zh301,Hx3,Zh61,Zh13,Sd and Nm)had reduced aboveground phosphorus utilization efficiency and weak physiological regulation ability,their leaf functions were severely damaged.[Conclusion]Different soybean varieties varied in their response to low phosphorus stress.Among the materials used,Qx1,Sy and Hx2 are comparatively more tolerant of low phosphorus and better suited to low phosphorus environments to ensure nor-mal growth,development and physiological activities.
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