不同 LED 光质对紫花苜蓿种子萌发及幼苗酚类化合物合成的影响.

The purpose of this study was to explore the effects of different LED light quality on the germination of alfalfa seeds and the content of photosynthetic pigments and phenolic compounds in seedlings, so as to provide a basis for further light quality control technology for the sprout vegetable production and industrial production of alfalfa plants. [Methods] The effects of 10 different LED light quality(red light R660 and R630, blue light B450 and B465, green light G520, yellow light Y590, red and blue combination R5B2, R1B1 and R2B5, white light W)on seed germination, seedling growth, anatomy, and phenolic compound synthesis of alfalfa‘WL656'were studied using dark treatment (D) as the control. [Results] Different treatments had no effect on the germination rate, germination potential and germination index of alfalfa seeds. Among monochromatic light treatments, both pure red lights promoted radicle elongation of alfalfa seedlings; B465 treatment significantly increased the stem diameter, epidermal cell thickness, cortical thickness, and individual vessel area of the hypocotyl of seedlings, and B450 significantly increased the diameter of vascular bundles. Different monochromatic light had no significant effect on chlorophyll a content, while the chlorophyll b content was lowest under two different blue light treatments, and the carotenoid content was highest under R660 treatment. Both pure blue lights promoted the accumulation of anthocyanins, total phenols and flavonoids in seedlings, but seedlings contained almost no anthocyanins under G520, Y590 and D treatments. R630 increased the chalcone synthase (CHS) activity in the hypocotyl, and G520 significantly increased the CHS activity in cotyledons. W increased the anthocyanin synthase (ANS) activity in the hypocotyl of seedlings, and Y590 increased the ANS activity in seedlings. Among the three combinations of red and blue light, with the decrease of red light ratio, stem diameter, cortical thickness and CHS activity in hypocotyl decreased, the content of root length, epidermal cell thickness, vascular bundle diameter, and anthocyanins of hypocotyls decreased first and then increased, and the content of photosynthetic pigments and CHS activity in seedling cotyledons increased. The content of total phenols and flavonoids in hypocotyl was highest under R2B5 treatment, and there was no difference in the content of three phenolic compounds in cotyledons. ANS activity in hypocotyl was the highest under R1B1 treatment, and ANS activity in cotyledon was the highest under R5B2 treatment. [Conclusions] Pure red light promoted seedling elongation after seed germination, pure blue light promoted the formation of anthocyanins, flavonoids, and total phenolsin seedlings, and the influence of red and blue combination light on the physiological characteristics of seedlings was more complicated. Taking into account the growth and physiological indicators, this study preliminarily believed that R2B5 treatment was a suitable LED light quality for the growth of alfalfa seedlings as it had moderate growth, high chlorophyll and phenolic content. [ABSTRACT FROM AUTHOR]