Light Intensity Modulates the Functional Composition of Leaf Metabolite Groups and Phyllosphere Prokaryotic Community in Garden Lettuce (Lactuca sativa L.) Plants at the Vegetative Stage.

Light intensity primarily drives plant growth and morphogenesis, whereas the ecological impact of light intensity on the phyllosphere (leaf surface and endosphere) microbiome is poorly understood. In this study, garden lettuce (Lactuca sativa L.) plants were grown under low, medium, and high light intensities. High light intensity remarkably induced the leaf contents of soluble proteins and chlorophylls, whereas it reduced the contents of leaf nitrate. In comparison, medium light intensity exhibited the highest contents of soluble sugar, cellulose, and free amino acids. Meanwhile, light intensity resulted in significant changes in the composition of functional genes but not in the taxonomic compositions of the prokaryotic community (bacteria and archaea) in the phyllosphere. Notably, garden lettuce plants under high light intensity treatment harbored more sulfur-cycling mdh and carbon-cycling glyA genes than under low light intensity, both of which were among the 20 most abundant prokaryotic genes in the leaf phyllosphere. Furthermore, the correlations between prokaryotic functional genes and lettuce leaf metabolite groups were examined to disclose their interactions under varying light intensities. The relative abundance of the mdh gene was positively correlated with leaf total chlorophyll content but negatively correlated with leaf nitrate content. In comparison, the relative abundance of the glyA gene was positively correlated with leaf total chlorophyll and carotenoids. Overall, this study revealed that the functional composition of the phyllosphere prokaryotic community and leaf metabolite groups were tightly linked in response to changing light intensities. These findings provided novel insights into the interactions between plants and prokaryotic microbes in indoor farming systems, which will help optimize environmental management in indoor farms and harness beneficial plant-microbe relationships for crop production.

Effects of light intensity and reduction of starter diet digestible lysine and metabolizable energy on broiler chicken growth performance, breast meat yield, and meat quality defects.

The etiology of Wooden Breast (WB) is unknown; therefore, it is difficult to produce broiler flocks with similar proportions of WB-affected and unaffected birds. Because WB has been detected as early as 15 d posthatch, the objective of this randomized complete block experiment with a 2 × 2 factorial treatment arrangement was to determine whether combining the effects of light intensity (LI) and early nutrient reduction strategies could reliably produce WB-affected and normal broilers to further investigate the physiological mechanisms underlying WB. On day of hatch, male, Ross 708 × Yield Plus broilers (n = 384; 16 birds per pen; 3 replicate blocks) were randomly allotted to floor pens in the same facility and exposed to either 2 (LOWLI) or 30 (HIGHLI) lux of light from d 0 to 35. Birds were fed either a commercial starter diet (CON) or the CON diet with a 10% reduction in both ME and digestible lysine (dLys; RED) from d 0 to 14 and then a common grower diet from d 15 to 35. Broiler growth performance, breast yield, and incidence and severity of WB and White Striping (WS) were assessed. Data were analyzed as a 2-way ANOVA with SAS PROC GLIMMIX and means separated at P < 0.05 with PDIFF. No interaction among LI and diet was observed (P > 0.05). Broilers reared with HIGHLI were heavier on d 35 and consumed more feed in all phases compared with broilers reared under LOWLI (P ≤ 0.0096). Broilers reared under LOWLI gained less BW from d 15 to 35 and d 0 to 35 compared with broilers reared under HIGHLI (P = 0.0073). Broilers fed the RED starter diet consumed more feed and had higher FCR from d 0 to 14 compared with broilers fed the CON diet (P ≤ 0.0012). In conclusion, combining reductions in LI and starter diet ME and dLys did not produce the hypothesized reductions in breast yield and incidence and severity of WB or WS.

Photosynthetic oxygen-supported algal-bacterial aerobic granular sludge can facilitate carbon, nitrogen and phosphorus removal from wastewater: Focus on light intensity selection.

Photosynthetic O2 is a promising alternative for mechanical aeration, the major energy-intensive unit in wastewater treatment plants. This study aimed to investigate the effects of light intensity varied from 190 to 1400 µmol·s-1·m-2 on photosynthetic O2-supported algal-bacterial aerobic granular sludge (AGS) system. Results indicate photosynthetic O2 can implement aerobic phosphorus (P) uptake and ammonia oxidation under the test illumination range even at dissolved oxygen concentration < 0.5 mg/L. An obvious O2 accumulation occurred after 60-90% nutrients being removed under 330-1400 µmol·s-1·m-2, and highly efficient ammonia removal, P uptake, and dissolved inorganic carbon removal were achieved under 670-1400 µmol·s-1·m-2. On the other hand, photosynthesis as O2 supplier showed little effect on major ions except for K+. This study provides a better understanding of the roles of light intensity on photosynthetic O2-supported algal-bacterial AGS system, targeting a sustainable wastewater industry.

The influence of spermidine on the build-up of fucoxanthin in Isochrysis sp. Acclimated to varying light intensities.

Spermidine is a type of important growth regulator, which involved in the biosynthesis of photosynthetic pigments, and has the function of promoting cell proliferation. In this study, Isochrysis sp. was selected as the research object to explore the effects of spermidine supplementation on the growth of algal cells and fucoxanthin synthesis under different light intensities. The results showed that the cell density (5.40 × 106 cells/mL) of algae were the highest at 11 days under the light intensity of 200 µmol·m-2·s-1 and spermidine content of 150 µM. The contents of diadinoxanthin (1.09 mg/g) and fucoxanthin (6.11 mg/g) were the highest when spermidine was added under low light intensity, and the growth of algal cells and fucoxanthin metabolism were the most significant. In the carotenoid synthesis pathway, PDS (phytoene desaturase) was up-regulated by 1.96 times and VDE (violaxanthin de-epoxidase) was down-regulated by 0.95 times, which may promote fucoxanthin accumulation.

Light Intensity Regulates Low-Temperature Adaptability of Tea Plant through ROS Stress and Developmental Programs.

Low-temperature stress limits global tea planting areas and production efficiency. Light is another essential ecological factor that acts in conjunction with temperature in the plant life cycle. However, it is unclear whether the differential light environment affects the low temperature adaptability of tea plant (Camellia sect. Thea). In this study, tea plant materials in three groups of light intensity treatments showed differentiated characteristics for low-temperature adaptability. Strong light (ST, 240 µmol·m-2·s-1) caused the degradation of chlorophyll and a decrease in peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and polyphenol oxidase (PPO) activities, as well as an increase in soluble sugar, soluble protein, malondialdehyde (MDA), and relative conductivity in tea leaves. In contrast, antioxidant enzyme activities, chlorophyll content, and relative conductivity were highest in weak light (WT, 15 µmol·m-2·s-1). Damage was observed in both ST and WT materials relative to moderate light intensity (MT, 160 µmol·m-2·s-1) in a frost resistance test. Chlorophyll degradation in strong light was a behavior that prevented photodamage, and the maximum photosynthetic quantum yield of PS II (Fv/Fm) decreased with increasing light intensity. This suggests that the browning that occurs on the leaf surface of ST materials through frost may have been stressed by the previous increase in reactive oxygen species (ROS). Frost intolerance of WT materials is mainly related to delayed tissue development and tenderness holding. Interestingly, transcriptome sequencing revealed that stronger light favors starch biosynthesis, while cellulose biosynthesis is enhanced in weaker light. It showed that light intensity mediated the form of carbon fixation in tea plant, and this was associated with low-temperature adaptability.

Effects of leaf-spreading on the volatile aroma components of green tea under red light of different intensities.

Spreading is an indispensable process in the aroma formation of green tea. The application of exogenous red-light spreading in tea processing has been verified to significantly improve the aroma of green tea, and endow tea with freshness, sweet flavor, and mellow taste. However, there were no previous studies investigating the effects of spreading with different red-light intensities on the aroma components of green tea. The aim of the present study was to evaluate the effect of the relationship between the aroma component and spreading with different red-light intensities (300 µmol∙m-2∙s-1, 150 µmol∙m-2∙s-1 and 75 µmol∙m-2∙s-1). As a result, a total of ninety-one volatile components were identified in this study. The orthogonal partial least squares discriminant analysis (OPLS-DA) model clearly distinguished the volatile components of green tea between different red-light intensities and obtained thirty-three differential volatile compounds. Combined with odor activity value (OAV > 1) analysis revealed that eleven volatile components were the key volatile compounds of green tea under different light conditions. Among them, 3-methyl-butanal, (E)-nerolidol, and linalool were the sources of chestnut-like aroma in green tea and were significantly accumulated under medium (MRL) and low intensity (LRL) red light. The results of the present study provided a theoretical basis that could guide green tea processing with red-light intensities to increase the aroma quality components of green tea.

Integrative analyses of transcriptome and metabolome reveal comprehensive mechanisms of Epigallocatechin-3-gallate (EGCG) biosynthesis in response to ecological factors in tea plant (Camellia sinensis).

Epigallocatechin-3-gallate (EGCG), a flavoured and healthy compounds in tea, is affected by the ecological factors. However, the biosynthetic mechanisms of EGCG in response to the ecological factors remian unclear. In this study, a response surface method with a Box-Behnken design was used to investigate the relationship between EGCG accumulation and ecological factors; further, integrative transcriptome and metabolome analyses were performed to explore the mechanism underlying EGCG biosynthesis in response to environmental factors. The optimal environmental conditions obtained for EGCG biosynthesis were as follows: 28℃, 70 % relative humidity of the substrate, and 280 µmol·m-2·s-1 light intensity; the EGCG content was increased by 86.83 % compared to the control (CK1). Meanwhile, the order of EGCG content in response to the interaction of ecological factors was as follows: interaction of temperature and light intensity > interaction of temperature and relative humidity of the substrate > interaction of light intensity and relative humidity of the substrate, indicating that temperature was the dominant ecological factors. EGCG biosynthesis in tea plants was found to be comprehensively regulated by a series of structural genes (CsANS, CsF3H, CsCHI, CsCHS, and CsaroDE), miRNAs (miR164, miR396d, miR5264, miR166a, miR171d, miR529, miR396a, miR169, miR7814, miR3444b, and miR5240), and transcription factors (MYB93, NAC2, NAC6, NAC43, WRK24, bHLH30, and WRK70); further, the metabolic flux was regulated and converted from phenolic acid to the flavonoid biosynthesis pathway based on accelerated consumption of phosphoenolpyruvic acid, d-erythrose-4-phosphate, and l-phenylalanine in response to ambient changes in temperature and light intensity. Overall, the results of this study reveal the effect of ecological factors on EGCG biosynthesis in tea plants, providing novel insights for improving tea quality.

Light plays a critical role in the accumulation of chlorogenic acid in Lonicera macranthoides Hand.-Mazz.

Light has important effects on plant metabolism. However, the relationship between the chlorogenic acid (CGA) content and light in plants remains unclear. Here, we investigated the effects of shading treatment on gene expression and CGA content in Lonicera macranthoides Hand.-Mazz. (LM), a widely used medicinal plant. A total of 1891 differentially expressed genes (DEGs) were obtained in flower buds and 819 in leaves in response to light in shading treatment compared to the control sample by RNA-Seq. After shading treatment, the content of CGA in LM leaves decreased significantly by 1.78-fold, the carotenoid content increased, and the soluble sugar and starch contents significantly decreased. WGCNA and the expression of related genes verified by qRT‒PCR revealed that CGA synthesis pathway enzyme genes form a co-expression network with genes for carbohydrate synthesis, photosynthesis, light signalling elements, and transcription factor genes (TFs) that affect the accumulation of CGA. Through a virus-induced gene silencing (VIGS) system and CGA assay in Nicotiana benthamiana (NB), we determined that downregulation of NbHY5 expression decreased the CGA content in NB leaves. In this study, we found that light provides energy and material for the accumulation of CGA in LM, and light affects the expression of CGA accumulation-related genes. Our results show that different light intensities have multiple effects on leaves and flower buds in LM and are able to coregulate LmHY5 expression and CGA synthesis.

Influencing factors for nutrient removal from piggery digestate by coupling microalgae and electric field.

Microalgae show great potential for nutrient removal from piggery digestate. However, full-strength piggery digestate have been found to severely inhibit microalgal growth. In this study, microalgae were coupled into the electric field (EF)system to form an electric field-microalgae system (EFMS). The effects of EF characteristics and environmental conditions on the growth of Desmodesmus sp. CHX1 and the removal of nitrogen and phosphorus in EFMS were explored. The results indicated that the optimal EF parameters for forming a fine EFMS were electrode of Zn (anode)/graphite (cathode), electric frequency of three times per day (10 min/time) and voltage of 12 V. The suitable light intensity and microalgae inoculation concentration for the EFMS were 180 µmol photons/(m2·s) and 0.2 g/L, respectively. Ammonium nitrogen and total phosphorus removal efficiencies were 65.38% and 96.16% in the piggery digestate by EFMS under optimal conditions. These results indicate that EFMS is a promising technology for nutrient removal from piggery digestate.

Effect of light intensity on growth performance and bone development of tibia in broilers.

Light management affects the health outcomes and growth performance of broiler chickens. However, the effects of different light intensities on growth performance and its association with tibia development of broilers remain unclear. In the present study, 462 Ross male broilers were divided into seven treatment groups with 6 replicates (11 birds per replicate), and then were subjected to different light intensity levels (0.5, 2, 5, 7, 9, 13 or 19 Lx) for 42 days. The results demonstrated that broilers under lower light intensity (2, 5Lx) obtained higher body weight (p < 0.05) and feed conversion ratio (p < 0.05). Lower light intensity exposure had no effects on the length, width, weight, breaking strength and the mineral density of the tibia (p > 0.05), but led to increased ash content and phosphorus during the starter phase (p < 0.05). Also, plasma levels of calcium (Ca), phosphorus (P) and alkaline phosphatase were increased in response to lower light intensity conditions (p < 0.05), but decreased under higher light intensity (p < 0.05), indicating dynamic mineral metabolic and depositional activity to light intensity. In addition, broilers exposed to lower intensity (0.5 Lx, 2 Lx and 5 Lx) during the starter phase had decreased hypertrophic chondrocytes (p < 0.05), but did not affect resting zone chondrocytes and proliferative chondrocytes of the growth plate (p > 0.05). In contrast, the light intensity did not affect the growth performance and the development of the tibia of broilers during the finishing phase. In summary, we demonstrated that lower light intensity promoted the growth performance and the bone development of broilers. Application of lower light intensity at the starter phase might be a management strategy for broiler industries.

Effect of Interactions between Phosphorus and Light Intensity on Metabolite Compositions in Tea Cultivar Longjing43.

Light intensity influences energy production by increasing photosynthetic carbon, while phosphorus plays an important role in forming the complex nucleic acid structure for the regulation of protein synthesis. These two factors contribute to gene expression, metabolism, and plant growth regulation. In particular, shading is an effective agronomic practice and is widely used to improve the quality of green tea. Genotypic differences between tea cultivars have been observed as a metabolic response to phosphorus deficiency. However, little is known about how the phosphorus supply mediates the effect of shading on metabolites and how plant cultivar gene expression affects green tea quality. We elucidated the responses of the green tea cultivar Longjing43 under three light intensity levels and two levels of phosphorus supply based on a metabolomic analysis by GC×GC-TOF/MS (Two-dimensional Gas Chromatography coupled to Time-of-Flight Mass Spectrometry) and UPLC-Q-TOF/MS (Ultra-Performance Liquid Chromatography-Quadrupole-Time of Flight Mass Spectrometry), a targeted analysis by HPLC (High Performance Liquid Chromatography), and a gene expression analysis by qRT-PCR. In young shoots, the phosphorus concentration increased in line with the phosphate supply, and elevated light intensities were positively correlated with catechins, especially with epigallocatechin of Longjing43. Moreover, when the phosphorus concentration was sufficient, total amino acids in young shoots were enhanced by moderate shading which did not occur under phosphorus deprivation. By metabolomic analysis, phenylalanine, tyrosine, and tryptophan biosynthesis (PTT) were enriched due to light and phosphorus effects. Under shaded conditions, SPX2 (Pi transport, stress, sensing, and signaling), SWEET3 (bidirectional sugar transporter), AAP (amino acid permeases), and GSTb (glutathione S-transferase b) shared the same analogous correlations with primary and secondary metabolite pathways. Taken together, phosphorus status is a crucial factor when shading is applied to increase green tea quality.

[Effect of light intensity on growth, accumulation of ginsenosides, and expression of related enzyme genes of Panax quinquefolius].

Appropriate light intensity is favorable for the photosynthesis, biomass accumulation, key enzyme activity, and secondary metabolite synthesis of medicinal plants. This study aims to explore the influence of light intensity on growth and quality of Panax quinquefolius. To be specific, sand culture experiment was carried out in a greenhouse under the light intensity of 40, 80, 120, and 160 µmol·m~(-2)·s~(-1), respectively. The growth indexes, photosynthetic characteristics, content of 6 ginsenosides of the 3-year-old P. quinquefolius were determined, and the expression of ginsenoside synthesis-related enzyme genes in leaves, main roots, and fibrous roots was determined. The results showed that the P. quinquefolius growing at 80 µmol·m~(-2)·s~(-1) light intensity had the most biomass and the highest net photosynthetic rate. The total biomass of P. quinquefolius treated with 120 µmol·m~(-2)·s~(-1) light intensity was slightly lower than that with 80 µmol·m~(-2)·s~(-1). The root-to-shoot ratio in the treatment with 120 µmol·m~(-2)·s~(-1) light intensity was up to 6.86, higher than those in other treatments(P<0.05),and the ginsenoside content in both aboveground and underground parts of P. quinquefolius in this treatment was the highest, which was possibly associated with the high expression of farnesylpyrophosphate synthase(FPS), squalene synthase(SQS), squalene epoxidase(SQE), oxidosqualene cyclase(OSC), dammarenediol-Ⅱ synthase(DS), and P450 genes in leaves and SQE and DS genes in main roots. In addition, light intensities of 120 and 160 µmol·m~(-2)·s~(-1) could promote PPD-type ginsenoside synthesis in leaves by triggering up-regulation of the expression of upstream ginsenoside synthesis genes. The decrease in underground biomass accumulation of the P. quinquefolius grown under weak light(40 µmol·m~(-2)·s~(-1)) and strong light(160 µmol·m~(-2)·s~(-1)) was possibly attributed to the low net photosynthetic rate, stomatal conductance, and transpiration rate in leaves. In the meantime, the low expression of SQS, SQE, OSC, and DS genes in the main roots might led to the decrease in ginsenoside content. However, there was no significant correlation between the ginsenoside content and the expression of synthesis-related genes in the fibrous roots of P. quinquefolius. Therefore, the light intensity of 80 and 120 µmol·m~(-2)·s~(-1) is beneficial to improving yield and quality of P. quinquefolius. The above findings contributed to a theoretical basis for reasonable shading in P. quinquefolius cultivation, which is of great significance for improving the yield and quality of P. quinquefolius through light regulation.

Effects of light intensity on the growth of Polygala fallax Hemsl. (Polygalaceae).

Polygala fallax Hemsl. (Polygalaceae), a traditional Chinese medicinal species, requires optimal growth conditions for artificial cultivation. Irradiance is one of the primary environmental factors that affects the growth and survival of P. fallax Hemsl. plants, which seemingly grow better under weak irradiance conditions. However, the optimum light intensity for growing P. fallax Hemsl. is not clear. To determine the optimum light intensity for cultivating this medicinal plant species, P. fallax Hemsl. plants from two different habitats were grown and exposed to three shade treatments (50% shade, 70% shade and 90% shade, which resulted in photosynthetically active radiation amounts equal to 662 µmol m-2 s-1, 401 µmol m-2 s-1, and 131 µmol m-2 s-1, respectively) to evaluate survival, growth, leaf photosynthesis, and the main pharmacological active ingredients (saponins) in response to shade. Our results revealed that the P. fallax Hemsl. plants in the different habitats consistently exhibited relatively high photosynthesis rates, biomass, survival rates and saponins under 662 µmol m-2 s-1 created by the 50% shade treatment. We concluded that photosynthetically active radiation of approximately 662 µmol m-2 s-1 is suitable for the cultivation of P. fallax Hemsl. plants.

Effects of Piperonyl Butoxide on the Accumulation of Lipid and the Transcript Levels of DtMFPα in Dunaliella tertiolecta.

As one of the sources of biodiesel, microalgae are expected to solve petroleum shortage. In this study, different concentrations of piperonyl butoxide were added to the culture medium to investigate their effects on the growth, pigment content, lipid accumulation, and content of carotenoids in Dunaliella tertiolecta. The results showed that piperonyl butoxide addition significantly decreased the biomass, chlorophyll content, and total carotenoid content but hugely increased the lipid accumulation. With the treatment of 150 ppm piperonyl butoxide combined with 8000 Lux light intensity, the final lipid accumulation and single-cell lipid content were further increased by 21.79 and 76.42% compared to those of the control, respectively. The lipid accumulation in D. tertiolecta is probably related to the increased expression of DtMFPα in D. tertiolecta under the action of piperonyl butoxide. The phylogenetic trees of D. tertiolecta and other oil-rich plants were constructed by multiple sequence alignment of DtMFPα, demonstrating their evolutionary relationship, and the tertiary structure of DtMFPα was predicted. In conclusion, piperonyl butoxide has a significant effect on lipid accumulation in D. tertiolecta, which provides valuable insights into chemical inducers to enhance biodiesel production in microalgae to solve the problem of diesel shortage.

Research Note: Effect of light intensity of calcium homeostasis in pullets.

The impact of varying light intensities on layer pullets is not yet well understood. Behaviorally, brighter illumination may increase pullet activity levels by allowing better navigation in the complexity of non-cage systems. In addition, light intensity was previously demonstrated to affect the levels of calcium and phosphate regulating hormones in mice. The objective of this study was to examine how exposure of pullets to different light intensity affects their calcium and phosphorus homeostasis. Lohmann LSL-Lite and Lohmann Brown-Lite pullets were randomized into 4 individually controlled rooms with 6 pens per room, which were assigned to 10 or 50 lux light intensity supplied via white LED lighting during the photophase. After 8 and 16 wk of exposure, plasma calcium, phosphorus, and magnesium were measured by inductively coupled plasma optical emission spectrometry; and parathyroid hormone, 1,25-dihydroxyvitamin D, fibroblast growth factor 23, and markers of bone formation and resorption were measured by ELISA. Intestine and kidney samples were collected at 16 wk and gene expression of receptors for calcium and phosphate regulating hormones was assessed. The data were analyzed by one-way ANOVA. Lohmann Brown-Lite pullets exposed to 50 lux for 8 wk exhibited lower ionized Ca levels and a trend for increased bone formation markers compared to pullets reared in 10 lux. Thus, higher light intensity during rearing may beneficially affect calcium homeostasis and bone formation in young Lohmann Brown-Lite chicken.

Roles of illumination on distribution of phosphorus in Chlorella vulgaris under mixotrophic cultivation.

Phosphorus (P) is a non-substitutable resource and global reserves of phosphate rock are limited. In this study, phosphorus recovery by Chlorella vulgaris, and the effects of different light intensities (2000 Lux, 5000 Lux, 8000 Lux, 12,000 Lux) on the phosphorus distribution in the soluble microbial product (SMP), extracellular polymeric substance (EPS) and intracellular polymeric substance (IPS) were analyzed. The results showed that the 5000 Lux was the optimum light intensity for P uptake and transformation by Chlorella vulgaris under mixotrophic cultivation. At the light intensity of 5000 Lux, the P uptake rate was 100% after 32 days of cultivation, and the concentration of intracellular organic phosphorus (OP) was 5.77 mg P/L. Moreover, EPS was the main P pool when inorganic phosphorus (IP) was depleted in bulk solution. Phosphorus recovery by microalgae is an important solution to treat P-containing wastewater.

Microalgae cultivation using unsterilized cattle farm wastewater filtered through corn stover.

The aim of this study was to investigate the cultivation of Chlorella sp. (FACHB-8) and Kirchneriella obesa (FACHB-2104) using the unsterilized cattle farm wastewater (CFW) filtered through corn stover. Corn stover filtration effectively reduced the turbidity and suspended solids of CFW and improved the adaptability of microalgae to CFW. The yields of microalgae supplemented with filtered CFW were significantly higher than those of microalgae supplemented with unfiltered CFW-by 14%-57% (FACHB-8) and 12%-78% (FACHB-2104) and comparable to those with pure blue-green algae medium (BG11). The growth kinetics of microalgae conformed to the DoseResp model. A 3:6 ratio of filtered CFW to BG11 and an 8000 lx light intensity were optimal for achieving high microalgae production. Under optimum conditions, the maximal yields of FACHB-8 and FACHB-2104 were 1.26 and 1.22 g/L, respectively, and the removal efficiencies of nitrogen, phosphorus, and chemical oxygen demand exceeded 95%, 99%, and 82%, respectively.

Stable isotope and photosynthetic response of tea grown under different temperature and light conditions.

The stable isotope and photosynthesis response of tea (Camellia sinensis) is determined under different light and temperature conditions. The results showed that isotopes of young tea leaves were more enriched with increasing light intensity (31 ~ 411 µmol m-2∙s-1). However, the value of δ13C and δ15N seemed depleted, while δ2H and δ18O became enriched as temperature increasing from 15 to 35 °C. Significant isotope differences were found in tea leaves harvested between early growth (0 ~ 10 days) and later growth (10 ~ 21 days) periods (p < 0.05). Pearson's correlation showed a negative correlation between isotopes (δ13C, δ15N and δ2H) and photosynthetic parameters (EVAP and CI) ranging from 0.497 to 0.872, under 25 °C/203 µmol m-2∙s-1. But δ18O had a weak correlation with all photosynthetic parameters under the same conditions. These distinctive correlations between isotopes and photosynthetic parameters provide new insights which could be used to predict tea isotope responses arising from subtle seasonal or climate change conditions.

Screening the Key Region of Sunlight Regulating the Flavonoid Profiles of Young Shoots in Tea Plants (Camellia sinensis L.) Based on a Field Experiment.

Both UV and blue light have been reported to regulate the biosynthesis of flavonoids in tea plants; however, the respective contributions of the corresponding regions of sunlight are unclear. Additionally, different tea cultivars may respond differently to altered light conditions. We investigated the responses of different cultivars ('Longjing 43', 'Zhongming 192', 'Wanghai 1', 'Jingning 1' and 'Zhonghuang 2') to the shade treatments (black and colored nets) regarding the biosynthesis of flavonoids. For all cultivars, flavonol glycosides showed higher sensitivity to light conditions compared with catechins. The levels of total flavonol glycosides in the young shoots of different tea cultivars decreased with the shade percentages of polyethylene nets increasing from 70% to 95%. Myricetin glycosides and quercetin glycosides were more sensitive to light conditions than kaempferol glycosides. The principal component analysis (PCA) result indicated that shade treatment greatly impacted the profiles of flavonoids in different tea samples based on the cultivar characteristics. UV is the crucial region of sunlight enhancing flavonol glycoside biosynthesis in tea shoots, which is also slight impacted by light quality according to the results of the weighted correlation network analysis (WGCNA). This study clarified the contributions of different wavelength regions of sunlight in a field experiment, providing a potential direction for slightly bitter and astringent tea cultivar breeding and instructive guidance for practical field production of premium teas based on light regimes.

Effects of Light on Secondary Metabolite Biosynthesis in Medicinal Plants.

Secondary metabolites (SMs) found in medicinal plants are one of main sources of drugs, cosmetics, and health products. With the increase in demand for these bioactive compounds, improving the content and yield of SMs in medicinal plants has become increasingly important. The content and distribution of SMs in medicinal plants are closely related to environmental factors, especially light. In recent years, artificial light sources have been used in controlled environments for the production and conservation of medicinal germplasm. Therefore, it is essential to elucidate how light affects the accumulation of SMs in different plant species. Here, we systematically summarize recent advances in our understanding of the regulatory roles of light quality, light intensity, and photoperiod in the biosynthesis of three main types of SMs (polyphenols, alkaloids, and terpenoids), and the underlying mechanisms. This article provides a detailed overview of the role of light signaling pathways in SM biosynthesis, which will further promote the application of artificial light sources in medicinal plant production.