Accumulation and distribution of N, P and K in Platycodon grandiflorum and their relationships to dry matter production

Platycodon grandiflorum is a Chinese traditional medicine and health food recorded by many ancient codices. It has beneficial effect on lung, heart, and respiration system. The planting area of Platycodon grandiflorum has been gradually increasing in China in the last few years. A field experiment was conducted to study the accumulation characteristics of dry matter, nitrogen, phosphorus and potassium of Platycodon grandiflorum and their relationship. The results showed that, the accumulated dry matter increased linearly with correlation coefficient being significant. Dry matter accumulation in stem, leaf, flower and fruit in P. grandiflorum increased throughout the whole growing period, while dry matter accumulation in root showed an inconstant tendency at different stages. At the seedling and flower stage, it was negative being -11.16 and -28.33 mg/(plant·d), respectively, resulting form the nutrients translating to aerial parts for the plant growth and development. At vigorous growth and fruiting stage, the rate of dry matter accumulation in root was picking up, being 44.01 and 38.33 mg/(plant·d), respectively. The nitrogen, phosphorus and potassium absorption capacity varied among different developing stages. The absorption capacity of N, P and K was comparatively lower within first 45 days after transplantation, which only accounted for 7.21%, 3.99%, and 5.53% of the total capacity, respectively. But it increased rapidly till 90 day after transplantation, which accounted for 64.78%, 56.57%, and 76.25% respectively, then it decreased. In general, the absorption capacity of N was the highest, followed by K and P. The N∶P∶K ratio was 1∶0.28∶0.48 taking the whole growing stages inconsideration.