Amur corktree (Phellodendron amurense) is one of the important accompany species in broad leaved-Korean pine forest, and the pharmaceutical resource plant of famous Chinese traditional medicine cortex phellodendri. Berberine, jatrorrhizine and palmatine are main alkaloids paid high attention by the researchers in amur corktree. In the present study, water stress treatments with four conditions, i.e. mild drought, severe drought, waterlogging and control (soil water potentials were controlled in the ranges of -40～-20 KPa、-80～-60 KPa、＜-80 KPa and -20～0 KPa) were performed using the technique of root-sphere osmotic irrigation in a soil pond. The changes of main medicinal compositions, berberine, jatrorrhizine and palmatine contents under different water conditions were discussed.
Berberine levels in amur corktree seedling differed in various organs. High berberine content was present in stem cortex, 36.6, 1.8 and 142.9 times as much as the peaks in stem xylem, root and leaves, respectively. Berberine accumulation induced in amur corktree seedlings after 20 days and significantly increased after 80 days under mild drought treatment. Berberine contents similarly lowered after 60 days and recovered after 80 days under severe drought and waterlogging compared to their respective controls. The variation of berberine content in the root under different conditions was similar to that in stem cortex. Berberine was mainly accumulated in stem cortex and root of seedlings, enhanced under mild drought treatment, whereas decreased under severe drought and waterlogging treatments compared to control (Fig. 1). Jatrorrhizine content in amur corktree seedlings was much lower than berberine. The stem cortex had relatively more jatrorrhizine, 22.3 and 4.3 times as much as stem xylem and root, whereas no jatrorrhizine was detected in leaves. Jatrorrhizine contents in stem cortex, stem xylem and root under mild drought treatment were higher than that of control. Jatrorrhizine levels in different organs were lower than or close to control under severe drought treatment. The waterlogging treatment lowered Jatrorrhizine levels in amur corktree seedlings. Thus, mild drought may induce the synthesis and accumulation of jatrorrhizine, and waterlogging might reduce jatrorrhizine content in amur corktree seedling (Fig. 2).
Palmatine content in amur corktree seedling was about 10% of berberine. It was abundant in stem cortex, and the maximum value was 20.1, 20.5, or 555 times as much as that in stem xylem, root and leaves respectively. Compared to control, palmatine contents were enhanced under mild drought treatment. No coincident effect on palmatine content was displayed under severe drought during the period of treatment. Under waterlogging, palmatine contents in stem cortex and xylem of the seedling was obviously lower than control. Similar to berberine and jatrorrhizine, mild drought was advantageous to palmatine, and waterlogging would inhibit palmatine in amur corktree seedling (Fig. 3).
The growth of amur corktree seedling was depressed under mild drought and waterlogging treatments. The plant height, stem diameter and biomass were clearly lower than control. Three alkaloids total production in control were the highest, and mainly distributed in stem cortex of seedlings. Our study showed that the mild drought improved the synthesis and accumulation of three alkaloids, but decreased biomass. Therefore, in the process of cultivation, a short time of mild drought treatment would activate alkaloids content, whereas more alkaloid yield would achieve with normal irrigation due to the effective accumulation of plant biomass.