Effect Of Lanthanum On Flavonoids Contents In Soybean Seedlings Exposed To Supplementary Ultraviolet-B Radiation

Effect of La(III) on the content,anti-oxidation and metabolic of flavonoid of soybean seedlings under elevated ultraviolet-B radiation (UV-B:0.15 W·cm^-2,0.45 W·cm^-2) was studied with hydroponics under laboratory conditions in this paper. The aim was to understand the mechanism of flavonoid in UV-B stress and posted the mechanism of RE which induced the plant fastness. It provided experiment gist for the lanthanon applied in agriculture. The main results were as follows:1. 20 mg·L^-1 of LaCl₃ can improve the content of the Chl, the UV-B absorbting compound and flavonoid of soybean seedling. Consequently it can alleviate the harm by UV-B radiation, and the protected effect on low dosage was better than high dosage; although UV-B radiation can improve the content of the Chl, UV-B absorbting compound and flavonoid of soybean seedling, the mechanism was different. The former one was advanced on its own initiative, while the latter one was stimulated passively.2. Under the low dosage of the UV-B stress, the soybean seedlings synthesized large amount of flavonoids in order to weaken the only flux of UV-B radiation entered inside and improve the ability of removing the excessive free bases inside. Under the high dosage of the intimidation of UV-B, the soybean seedlings can't synthesis large amount of flavonoid, the effective mechanism of alleviating the harm by UV-B radiation was that adjusted the component of flavonoid in order to produce more anti-oxidation flavonoid; while La(III) can effectively adjust the synthesis of flavonoids and eliminate ROS, so that it alleviated the harm to soybean seedlings by UV-B radiation.3. La(III) can accelerate the synthesis of flavonoids by improving the amount of Phe of soybean seedling and activity of the PAL, so thst it can reduce the only flux of UV-B radiation entered into plant; UV-B radiation decreased the content of IAA, although it can make some product of photosynthesis shift into the synthesis of flavonoids, the growth of the soybean delayed. La(III) alleviated the harm on plant growth by UV-B radiation through improving the relative content of IAA and restraining the acivity of IAA oxidatase, and made the contradiction between plant growth and flavonoids synthesis catabatic. La(III) decreased the amplitude of ABA, maybe it was related to that La(III) increased the content of flavonoids, alleviated the harm by UV-B radiation, stabilized the structure of cell membrane, keep the flow of water of plant, reduced the intensity of plant on the reaction of intimidate, decreased the accumulation of ABA. The accumulation of the product of photosynthesis not only was the substance base of growing of plant, but also was the precondition of the synthesis of flavonoids,the relationship between them was eat and flow.