| The viability of optimizing light quality in increasing plant growth and phytochemical concentration has been focused recently. Fore-researchers studied the effects of light quality on growth of plants but ignored the phytochemical changings, most studies examined only a few selected light qualities at one time and there are no reports examining the effects of all the important components of light quality (UV, B, green (G), R and RF) affecting plant growth and/or phytochemical accumulation in plants growing under what are otherwise the same environmental conditions.Therefore, using UV-A, blue (B), green (G), red (R), and far-red (FR) light-emitting diodes (LEDs), we investigated the effects of different supplemental light qualities on phytochemicals and growth of'Red Cross'baby leaf lettuce (Lactuca sativa L.) and Salvia miltiorrhiza Bunge, furthermore, the mechanism of why phytochemical concentration in plants increased by light quality changing has been studied. Findings from such a study will be useful to better understand the light quality affecting plant phytochemical synthesis, which is an important area in plant biology drawing much attention. The main results were as follows:1. Phytochemical concentration and growth of lettuce plants were significant affected by light quality treatments. The fresh weight, dry weight, stem length, leaf length and leaf width significantly increased with supplemental FR light compare to white light, presumably due to enhanced light interception by enlarged leaf area under supplemental FR light. Plant biomass was not significantly affected with supplemental UV-A, B, G and R treatments. Anthocyanins concentration increased with supplemental UV-A and B, respectively, carotenoids concentration increased with supplemental B, phenolics concentration increased with supplemental R while supplemental FR decreased anthocyanins, carotenoids and chlorophyll concentration compared to those in the white light control.2. Compare to white light control, anthocyanins concentration in lettuce increasing linearly with UV-A PF from 4.3μmol m-2 s-1 to 20.9μmol m-2 s-1, but xanthophylls,β-carotene, chlorophyll, total phenolics and ascorbic acid concentration in lettuce leaf were not significantly affected.3. Compare to white light control, growth and phytochemical concentrations of lettuce plants were significant improved by an alternative treatment of supplemental blue and far red light. Biomass production of lettuce significantly increased without losing of phytochemical concentration with supplemental blue/far red light. Biomass production of lettuce also significantly increased with supplemental far red / blue light but the anthocyanins and carotenoids concentration were significantly decreased.4. Compare to white light control, anthocyanins and carotenoids concentration were significantly increased with supplemental blue light, and phenolics concentration were significantly increased with supplemental red light, these were caused by the changings of both protective enzyme system and metabolism enzyme system. Enzyme activity of SOD, POD, PAL, TAT and PPO were significant increased by supplemental blue light, and enzyme activity of POD, TAT and PPO were significant increased by supplemental red light.5. Compare to white light control, growth and phytochemical concentration of Salvia miltiorrhiza Bunge were significant affected by light quality treatments. Plant height was significantly decreased with supplemental blue light, and the root length, root diameter, root fresh weight and root dry weight were significantly increased with supplemental red light. Salvianolic acid B concentration in Salvia miltiorrhiza Bunge was significantly increased with supplemental blue and red light, but TanshinoneIIA concentration was not significantly affected with supplemental blue and red light. These were caused by the changings of both protective enzyme system and metabolism enzyme system. Same to results in lettuce, enzyme activity of SOD, POD, PAL, TAT and PPO in Salvia miltiorrhiza Bunge were significant increased by supplemental blue light, and enzyme activity of POD, TAT and PPO were significant increased by supplemental red light.Part 1-3 were conducted at the University of Arizona, USA. Part 4 and 5 were conducted at the Northwest A&F University.
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