Effect Of Different LED Light Qualities On Physiological And Biochemical Characteristics And Chloroplast Ultrastructure Of Non-heading Chinese Cabbage

Non-heading Chinese cabbage plants (Brassica campestris L.ssp. chinensis Makino)of one cultivar(Xiu Lu) was selected as material in this study by measuring the growth of plants, Chlorophyll fluorescence, antioxidant enzyme systems, and chloroplast ultrastructure in plants of the cabbage to research the effect of different light qualities on plant morphology, cell inclusions, and chloroplast ultrastructure by using LED light sources. The main results are as follows:1. Under the LED light sources condition, the results indicated that the growth of roots was increased by using the red LED light(R) source while the blue light(B) promoted the elongation of stems and enlarged the leaf area. The effects of compound light qualities on plant morphology were insignificantly. The treatment with 7R/2B/1Y was benefited the growth of plants and promoted the accumulation of dry matter. The data showed that the root fresh weight, top dry weight, root dry weight and seedling index under 7R/2B/1Y treatment were significantly higher than other treatments.2. The content of carotenoids was enhanced by treating with R. Compound light qualities 7R/2B/1Y and 5R/4B/1Y increased the chlorophyll (chlorophyll a, chlorophyll b, chlorophyll a+b) significantly. The results indicated that supplement certain amount of yellow light (Y) based on different R/B ratio promoted the chlorophyll content of Chinese cabbage.3. The largest Fv/Fm signified the potential activity of Photosynthetic SystemⅡ(PSⅡ) under compound light quality7R/2B/1Y was higher than that under other treatments.ΦPSII was significantly higher than others under Y and 7R/2B/1Y .4. The contents of soluble sugar and MDA in the leaves have been increased by irradiating with R. B and compound light qualities had negative impact of the accumulation of soluble protein in the leaves of non-heading Chinese cabbage.5. SOD activity was elevated by treating with R or compound light quality with high R ratio. B promoted CAT activity while R increased APX activity significantly. POD activity of non-heading Chinese cabbage has been raised by compound light quality7R/2B/1Y and 1R/8B/1Y.6. The effect of different light qualities on chloroplast ultrastructure was different. R had little effect on the chloroplast structure-numerous grana thylakoid stacking, neat grana lamellae arrangement, and small starch grains. Y had negative impact on chloroplast structure-blurred grana lamellae with the gap inside. And there were no or rarely had starch particles under blue light. The chloroplast ultrastructure of non-heading Chinese cabbage was favorable by irradiating with compound light qualities 7R/2B/1Y and 5R/4B/1Y—numerous grana thylakoid stacking, clear grana lamellae, and a large number of moderate size oval starch grains which promoted the accumulation of dry matter.