Effects Of LED Lights On Flavonoid Synthesis In Sprouts Of Tartary Buckwheat

As a kind of edible herbs, tartary buckwheat (Fagopyrum tataricum Garetn) is rich in flavonoids. Particularly, rutin, the main flavonoid, has the biological function to stabilize blood pressure and blood sugar, and improve antioxidation activity. At present, tartary buckwheat has been received extensive attention as a functional health food due to its flavonoids. Furthermore, while buckwheat sprouts have the more flavonoids, free amino acids, minerals and crude fiber, they also show the features of easier mastication and special flavour. Due to the healthy characteristics, tartary buckwheat sprouts are pursued by the international vegetarian. In this study, after the tartary buckwheat sprouts were cultivated under the LED lights with different wavelength, the effects of the different lights on flavonoids synthesis were anlysized. So, this work would be the theoretical foundation and cultivation guidance for tartary buckwheat sprouts with higher quality. The results are as follows:1. When the tartary buckwheat seeds germinated for 6 days in darkness, the sprouts were cultivated under LED red light, LED white light, LED blue light, LED UV-B light and fluorescent light, respectively. They were grown under a 14h (day):8h (night) photoperiod at 27℃ for 3 days. The transcriptional levels of ten genes on the flavonoids biosynthesis pathway, FtPAL, FtC4H, Ft4CL, FtCHS, FtCHI, FtF3H, FtF3’H, FtFLS, FtDFR and FtANS, were investigated by semi-quantitative RT-PCR. Under the LED red light treatment, the results showed that the expression levels of Ft4CL, FtCHS and FtFLS were increased significantly (P< 0.05) in cotyledons, but only the expression level of FtFLS was improved observably in hypocotyls (P< 0.05). Under the LED white light treatment, when the expression levels of Ft4CL, FtCHS, FtFLS and FtANS were enhenced markablely (P< 0.05) in cotyledons, the expression levels of FtC4H, Ft4CL, FtCHS, FtF3H, FtDFR and FtANS were improved sharply (P< 0.05) in hypocotyls. Under LED blue light treatment, the expression levels of Ft4CL and FtF3H were increased significantly (P< 0.05) in cotyledons, the expression levels of FtCHI, FtF3’H and FtFLS were improved observably (P< 0.05) in hypocotyls. Under LED UV-B light treatment, while the other genes’ expression were extremely improved (P< 0.05) except FtDFR in cotyledons, the other genes’ expression were increased significantly(P< 0.05) except Ft4CL and FtF3’H in hypocotyls. Under fluorescent light treatment, when the expression levels of Ft4CL, FtFLS and FtDFR were up-regulated observably (P< 0.05) in cotyledons, the expression levels of FtC4H, FtCHI, FtF3H, FtFLS, FtDFR and FtANS were up-regulated significantly (P< 0.05) in hypocotyls. The results indicated that tartary buckwheat had the tissue-specifity of respones to different light. However, UV-B light could make a higher expression for almost genes significantly.2. The results of total flavonoids indicated the flavonoids were accumulated about 6.143%(mg/100mg dry weight) in cotyledons, and 0.993%(mg/100mg dry weight) in hypocotyls of tartary buckwheat sprouts. Under LED blue and UV-B light, their total flavonoids contents, the 1.42-fold and 2.07-fold of the control, were increased significantly in cotyledons (P< 0.01), but the other treatments showed no significant difference with control (P> 0.05). Under LED red, white, blue and UV-B light, their total flavonoids contents were enhanced dramatically in hypocotyls (P< 0.01), and they were the 1.82-fold,2.2-fold,2.73-fold and 5.86-fold of the control, respectively. Results indicated that tartary buckwheat had the tissue-specifity of respones to different light. Particularly, the LED blue and UV-B could cause sharply accumulation of total flavonoids in cotyledons and hypocotyls.3. Correlation coefficients between total flavonoids content and expression level of flavonoid biosynthesis related genes were analysized in cotyledon and hypocotyl of tartary buckwheat. Under these lights, total flavonoids content was significantly correlated with the expression levels of FtPAL, FtCHS, FtCHI, FtF3H and FtANS in cotyledons (correlation coefficients> 0.75). However, total flavonoids content showed a significant correlation with Ft4CL expression in hypocotyl (correlation coefficients=0.975). The results imply that the tartary buckwheat sprouts have the different regulatory mechanism of flavonoid biosynthesis in cotyledons and hypocotyls.