Abstract: We examined the effects of mineral nutrient deficiency on plant physiological characteristics and secondary metabolites. Sterile Houttuynia cordata seedlings were cultured under different element levels (including lack of P (T1), Ca (T2), Mg (T3), K (T4) and Fe (T5), and complete medium (CK) as a control) in solid media simulating soil environment for 30 days. The activities of superoxide dismutase (SOD) and peroxidase (POD), the contents of malondialdehyde (MDA), chlorophyll, phenols, and volatile components in the leaves, and the amount of oxalic acid secreted by the roots were analyzed. The results showed that leaves in the treatment groups were thin, prematurely aged (lack of P, Ca), yellow (lack of K), and less new roots (lack of Fe) in morphology. In terms of antioxidant stress, MDA content, SOD and POD activities were increased in different degrees, with MDA content increased by 99.7% (P<0.05, lack of Mg), SOD activity by 24.1% (P<0.05, lack of Ca), POD activity by 29.4% (P<0.05, lack of P). In terms of physiology and biochemistry, foliar chlorophyll content in treatment groups (lack of Mg, Fe and P) was significantly decreased by 29.4%, 59.9%, and 56.1% (P<0.05), respectively. The oxalic acid content was 4.84 μg·mL^-1, with an increase of 51.3% (P<0.05, lack of Fe). As for secondary metabolites, different treatments were beneficial to the accumulation of phenolics and volatiles. Under the condition with P, Ca, Mg and K deficiency, isoquercitrin increased by 259.7%, 213.7%, 177.1% and 411.7%, respectively (P<0.05), while chlorogenic acid increased by 108.2% (P<0.05, lack of K). Under P, Mg and K deficiency, cis-3-hexene ethyl ester increased by 130.1%, 160.3% and 166.9%, respectively (P<0.05), γ-terpinene increased by 140.3% (P<0.05, lack of Mg), and decanal and borneol increased by 125.2% and 227.2%, respectively (P<0.05, lack of Fe). Our results suggested that mineral nutrient deficiency affected the physiological characteristics and metabolites accumulation, providing theoretical basis for directional cultivation and medicinal use of H. cordata.

Key words: nutrient stress, malondialdehyde, superoxide dismutase, peroxidase, secondary metabolites.