Characteristics of andrographolide accumulation and carbon and nitrogen metabolisms in different growth periods of Andrographis paniculata(Burm.f.)Nees
[Objective]The present study aimed to clarify the accumulative characteristics of andrographolide,the major active component of Andrographis paniculata(Burm.f.)Nees,and carbon and nitrogen metabolism,as well as their relationship at different growth stages of A.paniculata,providing theoretical basis for the high-quality and high-yield cultivation management of A.paniculata.[Method]According to the growth and developmental characteristics of A.paniculata under field conditions,the phenological phase of A.paniculata was divided into six stages,tower stage,cluster stage,jointing stage,budding stage,flowering stage and fruit stage.The characteristics of biomass and andrographol-ide accumulation and carbon and nitrogen metabolisms in different growth stages were analyzed.[Result]The biomass of the whole plant and stem was stable at the flowering stage,while the biomass of leaves tended to be stable after the jointing stage.The relative growth rate and the proportion of leaf biomass gradually decreased with the growth process.The content of andrographolide in leaves gradually increased during the tower stage-budding stage(vegetative growth period),reached the peak at the budding stage and thereafter remained stable.The yield of andrographolide per plant reached its maximum at the flowering stage.The expression levels of key genes for andrographolide synthesis,e.g.ApDXS,ApDXR,ApGGPS and ApCPS,increased at the cluster stage and then decreased and stabilized,while ApHMGS and ApHMGR1 genes maintained at a high expression level after the budding stage.The synthesis of andrographolide could be mainly regulated by the mevalonate(MEP)pathway,and the accumulation of andrographolide lagged behind gene expression.The nitrogen content in leaves and stems gradually decreased with the growth of the plant,and the accumulation of nitrogen in the aboveground parts and stem reached the maximum value at the budding stage.After then,the nitrogen in leaves transferred to the fruits,resulting in gradually decreased accumulation.The activities of gluta-mine synthetase(GS),glutamate dehydrogenase(NAD-GDH),and isocitrate dehydrogenase(ICDH)in leaves were higher during the tower and cluster stages,as well as the content of sucrose and total soluble sugar in leaves.Subsequently,the activity of these enzymes and the con-tent of sucrose and total soluble sugar decreased.In contrast,starch content was increased.The content of andrographolide in leaves and the yield of andrographolide per plant were extremely significantly(P＜0.01,the same as below)positively correlated with plant height,biomass,aboveground nitrogen accumulation,and starch content,but extremely significantly negatively correlated with nitrogen content in leaves,indi-cating that promoting the accumulation of biomass during the vegetative growth period of the plant was beneficial for improving the content and yield of andrographolide.[Conclusion]The optimum harvesting period for the medicinal herb of A.paniculata is from the budding stage to the flowering stage.The vegetative growth period is the main period for nitrogen assimilation and accumulation in A.paniculata.During this peri-od,increasing nitrogen fertilizer appropriately can promote the accumulation of biomass in A.paniculata,improving the content and yield of andrographolide.
Andrographis paniculata(Burm.f.)NeesGrowth stagesCarbon and nitrogen metabolismAndrographolide
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