| Flavonoids are an important group of secondary products and play an important role in environmental adaptation and self-protection in plants. Environment is important factors influencing on the synthesis and accumulation of flavonoids and determines the composition and content of flavonoids. Hippophae neurocarpa of Elaeagnaceae family are distributed in the eastern edge of the Tibetan Plateau. The leaves are rich in flavonoids which have important medicinal value. In this study, using leaves of natural populations of H. neurocarpa as test materials, we measured leaf flavonoid compound concentration by HPLC technique, compare the differences of the leaf flavonoids compound and concentration of different places and analyze the spatial variation, and explored the relationships between the leaf flavonoids concentration and climatic factors(average growing season temperature, average rainfall in the growing season), and revealed the main factors influencing on the leaf flavonoid concentration. While using plantlets of H. neurocarpa as test materials, we measured three key enzymes phenylalanine ammonialyase(PAL), 4-hydroxy cinnamic acid enzyme(C4H) and 4-Coumadin acid coenzyme A ligase(4CL) activity of flavonoids metabolic pathways and flavonoid concentration under a temperature and drought stress, and explored the temperature and drought stress effect on the metabolism of flavonoids for providing a theoretical basis on the cultivation and management of sea-buckthorn. Conclusions are summarized as follows:(1) The geometric mean of myricetin, quercetin, kaempferol, isorhamnetin and the total flavonoid contcentration in H. neurocarpa were 0.031 mg g-1, 1.910 mg g-1, 1.098 mg g-1, 3.502 mg g-1 and 6.588 mg g-1 respectively. Kaempferol, isorhamnetin and the total flavonoid contcentration in H. neurocarpa were significantly negatively correlated with altitude. Myricetin contcentration in H. neurocarpa were significantly negatively correlated with longitude. Isorhamnetin contcentration in H. neurocarpa were significantly negatively correlated with longitude. Kaempferol contcentration in H. neurocarpa were significantly negatively correlated with latitude. Kaempferol contcentration was significantly positively correlated with the growing season average rainfall and quercetin(GSP). Myricetin, quercetin, isorhamnetin, kaempferol and the total flavonoid contcentration of H. neurocarpa were significantly negatively correlated with growing season average temperature(GST).(2) A significant difference for flavonoid metabolism in test-tube plantlets leaves of H. neurocarpaa under the different temperatures(P < 0.05). Regression analysis showed that the content of total flavonoids, quercetin, isorhamnetin,kaempferol and PAL, C4 H and 4CL activity were negatively related to the temperature. Low temperature stress was conducive to the increase of PAL, C4 H and 4CL activity and content of quercetin, kaempferol, isorhamnetin, flavonoids and carotenoids, but not conducive to the accumulation myricetin content. Under temperature stress, plantlets of Hippophae neurocarpa synthesized high concentrations of flavonoids through the activation of a key enzyme activity in phenylpropanoid pathway.(3) A significant difference for PAL,C4 H and 4CL is found in test-tube plantlets leaves of H. neurocarpaa under the drought stress(P < 0.05).With the serious of drought stress,the activity of PAL is significantly increased.The activity of C4 H and 4CL increased at first,and then decreased,which reaches the highest value under 20% PEG-6000.The content of myricetin, quercetin, kaempferol and total flavonoids were associated with PAL, C4 H and 4CL activity negatively correlated. Although the related enzyme activities are increased by drought stress, the content of myricetin, quercetin, kaempferol and total flavonoid in test-tube plantlets leaves of H. neurocarpaa is not significantly increase, which may be more intermediary metabolism biological products for secondary metabolites such as lignin synthesis. |
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