Hemin-induced increase in saponin content contributes to the alleviation of osmotic and cold stress damage to Conyza blinii in a heme oxygenase 1-dependent manner

Hemin can improve the stress resistance of plants through the heme oxygenase system.Additionally,substances contained in plants,such as secondary metabolites,can improve stress resistance.However,few studies have explored the effects of hemin on secondary metabolite content.Therefore,the effects of hemin on saponin synthesis and the mechanism of plant injury relief by hemin in Conyza blinii were investigated in this study.Hemin treatment promoted plant growth and increased the antioxidant enzyme activity and saponin content of C.blinii under osmotic stress and cold stress.Further study showed that hemin could provide sufficient precursors for saponin synthesis by improving the photosynthetic capacity of C.blinii and increasing the gene expression of key enzymes in the saponin synthesis pathway,thus increasing the saponin content.Moreover,the promotion effect of hemin on saponin synthesis is dependent on heme oxygenase-1 and can be reversed by the inhibitor Zn-protoporphyrin-IX(ZnPPIX).This study revealed that hemin can increase the saponin content of C.blinii and alleviate the damage caused by abiotic stress,and it also broadened the understanding of the relationship between hemin and secondary metabolites in plant abiotic stress relief.

Roles of hydroxyl and oxygen vacancy of CeO_(2)·xH_(2)O in Pd-catalyzed ethanol electro-oxidation

In the field of noble metal-catalyzed alcohol electro-oxidation reaction(AOR),huge attention is paid on the composition,size,facet,and structure of the metals,while the support engineering should also be emphasized.CeO_(2)has been widely used as a unique support in AOR,primarily due to its abundant oxygen vacancies(O_(v)).Herein,we report CeO_(2)·xH_(2)O nanoparticles with both massive hydroxyl groups(OH)and O_(v)remarkably enhance the catalytic activity and stability of Pd toward ethanol oxidation reaction(EOR).The CO striping experiments and density functional theory(DFT)calculations suggest that OH and O_(v)on CeO_(2)·xH_(2)O surface bring about a large downshift of Pd d-band center and a significant weakening of CO absorption on Pd.Moreover,OH and O_(v)also play synergic roles in the removal of toxic intermediates.Consequently,the important roles of OH and O_(v)of CeO_(2)·xH_(2)O are confirmed in Pd-catalyzed EOR.The facile CeO_(2)·xH_(2)O-enhanced strategy can contribute to the catalyst design for other energy conversion reactions.