Effect of nitrogen forms on berberine, jatrorrhizine and palmatine content in corktree seedlings

Nitrogen nutrition is one of the important environmental factors that affect plant growth and secondary metabolism. It's a key and active element in plant nutrition. Corktree (Phellodendron amurense) is a valuable resource for both lignum and Chinese traditional medicine. It is listed at the second place as one of national protected plants in China. Berberine, jatrorrhizine and palmatine are three main bioactive alkaloids in corktree. In this paper, effect of nitrogen forms on alkaloid contents was investigated through changes of NH~+_4-N and NO~-_3-N ratios in culture medium. Response of berberine, jatrorrhizine and palmatine content to the ratio of NH~+_4-N and NO~-_3-N in roots and stems of corktree seedlings were different. In roots after 33 days of treatment, alkaloid contents declined as the treatment time increased, while the levels in stems increased. Berberine content was clearly affected by different nitrogen forms. The level fluctuated in the early 22 days of treatment, and then started to respond to the ratio of NH~+_4-N and NO~-_3-N in culture medium. High ratio of NO~-_3-N and NH~+_4-N enhanced berberine accumulation in roots and stems (figure 1-a, figure 1-b). High NO~-_3-N levels favor the accumulation of jatrorrhizine in roots until treatment of 46 days (figure 2-a). No significant correlation was found between jatrorrhizine content and the ratio of NH~+_4-N and NO~-_3-N in stems. The level was high when the ratio of NH~+_4-N and NO~-_3-N was 75/25 or 25/75 (figure 2-b). The responses of palmatine levels in roots and stems to NH~+4-N and NO~-3-N ratios were similar. During late stage of treatment, higher NH~+4-N/NO~-3-N gave lower palmatine levels except a NH~+4-N and NO~-3-N of 0/100 (figure 3-a, figure 3-b). Different nitrogen forms affect the growth of corktree seedlings, as well as the contents of berberine, jatrorrhizine and palmatine. If the effect of nitrogen forms on the growth of corktree seedlings were taken into account, berberine production (product of content and biomass) was highest at 0/100 of NH~+_4-N/NO~-_3-N ratio. As a whole, the optimal nitrogen condition was 25/75 of NH~+_4-N/NO~-_3-N ratio for both jatrorrhizine and palmatine accumulation. While berberine accumulation was a little different from those of jatrorrhizine and palmatine, berberine production per plant was high when the ratio of NH~+_4-N and NO~-_3-N was 0/100 (table 2).