Comparative metabolic activity related to flavonoid synthesis in leaves and flowers of Chrysanthemum morifolium in response to K deficiency

K limitation could decrease the flavonoids content in many Chinese traditional herbs. These results may be caused by the influence of K deficiency on the synthesis pathway of flavonoids. In this paper, we aim to study the influence of K deficiency on secondary metabolites and activities of phenylalanine ammonia lyase (PAL), 4-coumarate coenzyme A ligase (4CL) and cinnamate 4-hydroxylase (C4H) enzymes in the process of flavonoid synthesis in Chrysanthemum morifolium Ramat. The results show that K deficiency decreased the flavonoid and chlorogenic acid contents slightly in flower of C. morifolium while the same effect was obtained on C4H and PAL. Total flavonoids content increased with the content of cinnamic acid and p-coumaric acid in the plant under K deficiency, respectively. The regression equations between content of flavonoids and cinnamic acid/ p-coumaric acid should be expressed in term of linear effects (R2 = 0.9809, P < 0.001 for cinnamic acid and R2 = 0.9929, P < 0.0001 for p-coumaric acid, respectively). But the effect of phenylalanine on flavonoids should be expressed in term of quadratic pattern (R2 = 0.9375, P < 0.05). There were two kinds principal components from chorismate to coumaryl CoA synthesis process, principal 1 was the substrate (phenylalanine, cinnamic acid, p-coumaric acid and PAL) and principal 2 was the enzyme (4CL, C4H), the principal 1 was the domination principal in both K deficient (88.36% and 10.57%) and sufficient treatments (88.17% and 9.64%), however, the factor loading (correlation coefficient of measured targets and the corresponding principal component) in principal 1 was opposite under different K application.