Arbuscular mycorrhizal fungi inoculation and exogenous indole-3-acetic acid application induce antioxidant defense response to alleviate cadmium toxicity in Broussonetia papyrifera

Cadmium(Cd)contamination in soil poses a huge threat to plants even at low concentrations;Broussonetia papyrifera has great potential in remediation of soil heavy metal contamination.However,whether exogenous indole-3-acetic acid(IAA)application and arbuscular mycorrhizal fungi(AMF)have synergistic effects on Cd tolerance of B.papyrifera remains unclear.To investigate the effects of AMF inoculation and IAA application on the tolerance of B.papyrifera to Cd stress,two experiments were conducted:the first to investigate the effect of AMF(Rhizophagus irregularis)inoculation on the tolerance of B.papyrifera to Cd stress and the second to investigate the combined effects of AMF inoculation and IAA application on the tolerance of B.papyrifera to Cd stress.Parameters including endogenous hormone concentration,antioxidant defense response,malondialdehyde(MDA)content,and gene expression related to antioxidant enzyme system and hormone were measured.The results indicated that AMF alleviated Cd toxicity of B.papyrifera by reducing MDA content and improving antioxidant enzyme activities and Cd absorption capacity.Furthermore,the combination of AMF inoculation and IAA application had a synergetic effect on the tolerance of B.papyrifera to Cd stress through upregulating BpAUX1 and BpAUX2,which might contribute to root growth and root xylem synthesis,and by upregulating BpSOD2 and BpPOD34 to enhance the antioxidant enzyme system.This work provides a new insight into the application of IAA in the remediation of soil Cd pollution by mycorrhizal plants.

Microstructure,tensile properties and thermal stability of AlMgSiScZr alloy printed by laser powder bed fusion

The new generation of Sc and Zr modified Al alloys has been attracted wide concerns in aerospace industry,owing to the excellent mechanical performances and superior thermal stability than other normal Al alloys.By microalloying with Sc and Zr,the Al3(Sc,Zr)particle forms as the grain refiner during the solidification,which is extremely beneficial for the laser powder bed fusion(LPBF)processed Al alloys.In this study,a new type Al-14.1 Mg-0.47 Si-0.31 Sc-0.17 Zr alloy was additively manufactured by LPBF,and the microstructure,tensile properties and thermal stability were studied in detail.By using a single melt-67°scanning strategy,the LPBF-processed specimen with a relative density of 99.4%and tensile strength of 487.7 MPa was obtained at 160 W-200 mm/s.And this AlMgSiScZr alloy can still exhibit an excellent tensile strength of 393.9 MPa at a moderate temperature of 473 K.After the aging treatment,the tensile properties further increased due to the precipitate hardening of Mg2Si and Al3(Sc,Zr),and the maximum value(580 MPa)was reached at an aging time of 10 h.The average crystal size was almost unchanged after aging treated at 325℃and 24 h,indicating this AlMgSiScZr alloy has an improved thermal stability.The AlMgSiScZr alloy is recommended to substitute some particular titanium alloys in aerospace field afterwards.