Chrysanthemum morphology, photosynthetic efficiency and antioxidant capacity are differentially modified by light quality

Manipulating the light spectrum to increase the biomass production, physiological plasticity and nutritional quality of Eruca sativa L

The extensive development in light-emitting diodes (LEDs) in recent years provides an opportunity to positively influence plant growth and biomass accumulation and to optimize biochemical composition and nutritional quality. This study aimed to assess how different light spectra affect the growth, photosynthesis and biochemical properties of Eruca sativa. Therefore two LED lighting modes - red:blue (RB, 1:1) and red:green:blue (RGB, 2:1:2) were compared to the conventional white light fluorescent tubes (WL). Plant biomass, photosynthetic performance, several antioxidants, polyamines and nitrates contents were analyzed across different treatments. The plant growth was affected by the light quality - the presence of green light in the spectrum resulted in smaller plants and leaves, and correspondingly less biomass. RB spectral mode enhanced the total antioxidant and guaiacol peroxidase activity, pigments, flavonoids, polyphenols, ascorbate and polyamines contents. This effect under RB was combined with better leaf development compared to RGB and less nitrate in the leaves among all treatments. The RB light generated modifications in polyamines, which are interrelated with the nitrate content, further induce important metabolite and antioxidant changes. Both RB and RGB enhanced photosynthesis. The afterglow thermoluminescence band varied according to leaves development, being higher in RB and WL as a consequence of their faster growth. The RB light spectrum was found to be the most efficient for promoting the growth, biochemical composition, and overall quality of Eruca sativa compared to RGB and WL. These findings suggest that RB LEDs can be an effective tool for improving crop production in controlled environments.

Effects of LED polarized and vortex light on growth and photosynthetic characteristics of pepper (Capsicum annuum L.)

Most studies currently focus on traditional illuminant regulating plant growth, while less attention has been given to the LED internal luminescence. This study examined how polarized and vortex light affect the growth and photosynthetic traits of pepper plants, with LED light used as the control. The findings indicated that circular polarized light significantly increased the aboveground biomass of pepper. Additionally, both polarized and vortex light treatment significantly influenced the root development of pepper. In comparison to the control group, the chlorophyll content was highest under circular polarized light, while the Pn, Sc, Tr, and Ci values were highest under linear polarized light, and the enzyme activity of Rubisco was increased. Circular polarized light notably increased the activities of POD, CAT, and SOD, the activity of SOD reached its peak under the left vortex light. Moreover, the content of MDA was observed to be the lowest under linear and right vortex light treatments. The expressions of key genes for chlorophyll synthesis (CaHEMA1 and CaCAO) and antioxidant enzyme synthesis (CaPOD, CaSOD, and CaMDHAR) were significantly altered under varying polarized light conditions, The latter genes, which play crucial roles in antioxidant enzyme activity, also showed significant variations in response to different polarized light treatments. In conclusion, polarized light significantly impacts the growth of pepper and is anticipated to be utilized for plant growth, setting the stage for future research in this area.

Evaluation of Environmental Factor Effects on the Polyphenol and Flavonoid Content in the Leaves of Chrysanthemum indicum L. and Its Habitat Suitability Prediction Mapping

The leaves of Chrysanthemum indicum L. are known to have various bioactive compounds; however, industrial use is extremely limited. To overcome this situation by producing high-quality leaves with high bioactive content, this study examined the environmental factors affecting the phytochemical content and antioxidant activity using C. indicum leaves collected from 22 sites in Kochi Prefecture, Japan. Total phenolic and flavonoid content in the dry leaves ranged between 15.0 and 64.1 (mg gallic acid g-1) and 2.3 and 11.4 (mg quercetin g-1), while the antioxidant activity (EC50) of the 50% ethanol extracts ranged between 28.0 and 123.2 (µg mL-1) in 1,1-Diphenyl-2-picrylhydrazyl radical scavenging assay. Among the identified compounds, chlorogenic acid and 1,5-dicaffeoylquinic acid were the main constituents in C. indicum leaves. The antioxidant activity demonstrated a positive correlation with 1,5-dicaffeoylquinic acid (R2 = 0.62) and 3,5-dicaffeoylquinic acid (R2 = 0.77). The content of chlorogenic acid and dicaffeoylquinic acid isomers varied significantly according to the effects of exchangeable magnesium, cation exchange capacity, annual temperature, and precipitation, based on analysis of variance. The habitat suitability map using the geographical information system and the MaxEnt model predicted very high and high regions, comprising 3.2% and 10.1% of the total area, respectively. These findings could be used in future cultivation to produce high-quality leaves of C. indicum.

Exploring Plants with Flowers: From Therapeutic Nutritional Benefits to Innovative Sustainable Uses

Flowers have played a significant role in society, focusing on their aesthetic value rather than their food potential. This study's goal was to look into flowering plants for everything from health benefits to other possible applications. This review presents detailed information on 119 species of flowers with agri-food and health relevance. Data were collected on their family, species, common name, commonly used plant part, bioremediation applications, main chemical compounds, medicinal and gastronomic uses, and concentration of bioactive compounds such as carotenoids and phenolic compounds. In this respect, 87% of the floral species studied contain some toxic compounds, sometimes making them inedible, but specific molecules from these species have been used in medicine. Seventy-six percent can be consumed in low doses by infusion. In addition, 97% of the species studied are reported to have medicinal uses (32% immune system), and 63% could be used in the bioremediation of contaminated environments. Significantly, more than 50% of the species were only analysed for total concentrations of carotenoids and phenolic compounds, indicating a significant gap in identifying specific molecules of these bioactive compounds. These potential sources of bioactive compounds could transform the health and nutraceutical industries, offering innovative approaches to combat oxidative stress and promote optimal well-being.

The effect of a chrysanthemum water extract in protecting the retina of mice from light damage

Background

Oxidative stress can induce age-related diseases. Age-related retinal diseases, such as age-related macular degeneration (AMD), are difficult to cure owing to their complicated mechanisms. Although anti-neovascular therapeutics are used to treat wet AMD, vision cannot always be completely restored, and disease progression cannot always be inhibited. Therefore, determining a method to prevent or slow retinal damage is important. This study aimed to investigate the protective effect of a chrysanthemum water extract rich in flavone on the oxidatively stressed retina of mice.

Methods

Light damage was induced to establish oxidative stress mouse models. For in vitro experiments, ARPE-19 cells were cultured and divided into four groups: control, light-damaged, and low- and high-dose chrysanthemum extract. No treatment was administered in the control group. The light-damaged and low- and high-dose chrysanthemum extract groups were exposed to a similar white light level. The chrysanthemum extract was added at a low dose of 0.4 mg/mL or a high dose of 1.0 mg/mL before cell exposure to 2500-lx white light. Reactive oxygen species (ROS) level and cellular viability were measured using MTT and immunofluorescence staining. For in vivo experiments, C57BL/6 J mice were divided into the same four groups. Low- (0.23 g/kg/day) and high-dose (0.38 g/kg/day) chrysanthemum extracts were continuously intragastrically administered for 8 weeks before mouse exposure to 10,000-lx white light. Retinal function was evaluated using electroretinography. In vivo optical coherence tomography and in vitro haematoxylin and eosin staining were performed to observe the pathological retinal changes in each group after light damage. Fluorescein fundus angiography of the arteriovenous vessel was performed, and the findings were analysed using the AngioTool software. TUNEL immunofluorescence staining was used to assess isolated retinal apoptosis.

Results

In vitro, increased ROS production and decreased ARPE-19 cell viability were found in the light-damaged group. Improved ARPE-19 cell viability and reduced ROS levels were observed in the chrysanthemum extract treatment groups. In vivo, dysfunctional retinas and abnormal retinal structures were found in the light-damaged group, as well as increased apoptosis in the retinal ganglion cells (RGCs) and inner and outer nuclear layers. The apoptosis rate in the same layers was lower in the chrysanthemum extract treatment groups than in the light-damaged group. The production of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), increased in the treatment groups. NF-κB in the nucleus and TNF-α were more highly expressed in the light-damaged group than in the low- and high-dose chrysanthemum extract groups.

Conclusions

Light damage-induced retinal oxidative stress can lead to ROS accumulation in the retinal tissues. Herein, RGC and photoreceptor layer apoptosis was triggered, and NF-κB in the nucleus and TNF-α were highly expressed in the light-damaged group. Preventive chrysanthemum extract administration decreased ROS production by increasing SOD, CAT, and GSH-Px activities and reversing the negative changes, demonstrating a potential protective effect on the retina.

Red Light Enhances the Antioxidant Properties and Growth of Rubus hongnoensis

The purpose of this study was to determine the effect of light quality on R.hongnoensis growth, physiology, and antioxidant properties. Five light conditions were employed, including white (control), red (R), blue (B), combined LED of R, green (G), and B at 7:1:2 (RGB), as well as combined LED of R, G, B, and far-red (Fr) at 7:1:2:1 (RGBFr). R light had the greatest growth-promoting effect based on plant height, leaf length, leaf width, stem diameter, and leaf area. However, leaf width and root length exhibited the greatest growth under RGB. The fresh and dry weight of shoots and roots were highest under R and RGB light. Photosynthesis was highest under RGB and lowest under B. Transpiration was highest in RGBFr. Stomatal conductance and photosynthetic water use efficiency were greatest under RGBFr. Total phenol content and radical scavenging activity were highest under R, while total flavonoid content was highest under RGB. Superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities were upregulated under W, whereas guaiacol peroxidase (GPX) activity was highest under RGB. The present results suggest that, among the tested light treatments, R light was most conductive for vegetative growth and antioxidant capacity in R. hongnoensis.

Comparison of the transcriptomic responses of two Chrysanthemum morifolium cultivars to low light

BACKGROUND

Low light is a primary regulator of chrysanthemum growth. Our aim was to analyse the different transcriptomic responses of two Chrysanthemum morifolium cultivars to low light.

METHODS AND RESULTS

We conducted a transcriptomic analysis of leaf samples from the 'Nannonggongfen' and 'Nannongxuefeng' chrysanthemum cultivars following a 5-day exposure to optimal light (70%, control [CK]) or low-light (20%, LL) conditions. Gene Ontology (GO) classification of upregulated genes revealed these genes to be associated with 11 cellular components, 9 molecular functions, and 15 biological processes, with the majority being localized to the chloroplast, highlighting the role of chloroplast proteins as regulators of shading tolerance. Downregulated genes were associated with 11 cellular components, 8 molecular functions, and 16 biological processes. Heat map analyses suggested that basic helix-loop-helix domain genes and elongation factors were markedly downregulated in 'Nannongxuefeng' leaves, consistent with the maintenance of normal stem length, whereas no comparable changes were observed in 'Nanonggongfen' leaves. Subsequent qPCR analyses revealed that phytochrome-interacting factors and dormancy-associated genes were significantly upregulated under LL conditions relative to CK conditions, while succinate dehydrogenase 1, elongated hypocotyls 5, and auxin-responsive gene of were significantly downregulated under LL conditions.

CONCLUSIONS

These findings suggest that LL plants were significantly lower than those of the CK plants. Low-light tolerant chrysanthemum cultivars may maintain reduced indole-3-acetic acid (IAA) and elongation factor expression as a means of preventing the onset of shade-avoidance symptoms.

Analyses of the photosynthetic characteristics, chloroplast ultrastructure, and transcriptome of apple (Malus domestica) grown under red and blue lights

BACKGROUND

Light quality significantly affects plant growth and development, photosynthesis, and carbon and nitrogen metabolism. Apple (Malus domestica Borkh.) is a widely cultivated and economically important fruit crop worldwide. However, there are still few studies on the effects of different light qualities on the growth and development of apple seedlings.

RESULTS

In this study, we explored the effects of blue and red light treatments on the growth and development, photosynthetic characteristics, leaf chloroplast ultrastructure, and carbon and nitrogen metabolism of apple seedlings. Blue light significantly inhibited apple plant growth and leaf extension, but it promoted the development of leaf tissue structures and chloroplasts and positively affected leaf stomatal conductance, the transpiration rate, and photosynthetic efficiency. The red light treatment promoted apple plant growth and root development, but it resulted in loosely organized leaf palisade tissues and low chlorophyll contents. The blue and red light treatments enhanced the accumulation of ammonium nitrogen in apple seedlings. Moreover, the blue light treatment significantly promoted nitrogen metabolism. Additionally, an RNA-seq analysis revealed that both blue light and red light can significantly up-regulate the expression of genes related to carbon and nitrogen metabolism. Blue light can also promote amino acid synthesis and flavonoid metabolism, whereas red light can induce plant hormone signal transduction. The expression of a gene encoding a bHLH transcription factor (MYC2-like) was significantly up-regulated in response to blue light, implying it may be important for blue light-mediated plant development.

CONCLUSIONS

Considered together, blue and red light have important effects on apple growth, carbon and nitrogen metabolism. These findings may be useful for determining the ideal light conditions for apple cultivation to maximize fruit yield and quality.

Blue Light Improves Photosynthetic Performance during Healing and Acclimatization of Grafted Watermelon Seedlings

To investigate the importance of light on healing and acclimatization, in the present study, grafted watermelon seedlings were exposed to darkness (D) or light, provided by blue (B), red (R), a mixture of R (68%) and B (RB), or white (W; 35% B, 49% intermediate spectra, 16% R) LEDs for 12 days. Survival ratio, root and shoot growth, soluble carbohydrate content, photosynthetic pigments content, and photosynthetic performance were evaluated. Seedling survival was not only strongly limited in D but the survived seedlings had an inferior shoot and root development, reduced chlorophyll content, and attenuated photosynthetic efficiency. RB-exposed seedlings had a less-developed root system. R-exposed seedlings showed leaf epinasty, and had the smallest leaf area, reduced chlorophyll content, and suppressed photosynthetic apparatus performance. The R-exposed seedlings contained the highest amount of soluble carbohydrate and together with D-exposed seedlings the lowest amount of chlorophyll in their scions. B-exposed seedlings showed the highest chlorophyll content and improved overall PSII photosynthetic functioning. W-exposed seedling had the largest leaf area, and closely resembled the photosynthetic properties of RB-exposed seedlings. We assume that, during healing of grafted seedlings monochromatic R light should be avoided. Instead, W and monochromatic B light may be willingly adopted due to their promoting effect on shoot, pigments content, and photosynthetic efficiency.

Leaf development and energy yield of hydroponic sweetpotato seedlings using single-node cutting as influenced by light intensity and LED spectrum

Vine cuttings with six to eight unfolded leaves are utilized as is conventional in sweetpotato (Ipomoea batatas (L.) Lam.) seedling production. However, most vine cuttings wilt after transplanting into the field. Moreover, few researchers have examined the influence of photon flux density (PFD) provided by white or white plus red light-emitting diodes (LEDs) on sweetpotato plantlets. In this study, hydroponic sweetpotato (cv. Beniharuka) seedlings using single-node cutting were grown under 20 combinations of five levels of PFDs of 150, 200, 250, 300, and 350 μmol m^-2 d^-1 and four light qualities: white LEDs with a red light to blue light ratio (R:B ratio) of 0.9, white plus red LEDs with R:B ratios of 1.2 and 2.2, respectively, and fluorescent lamp with an R:B ratio of 1.8 as control, for 20 days under a controlled enviroment. Results showed that the number of newly developed leaves on hydroponic sweetpotato seedlings increased with time in a quadratic function, regardless of light quality. Fluorescent lamps led to greater numbers of new leaves on hydroponic sweetpotato seedlings compared with those grown under LEDs. Plant height, leaf area, and fresh and dry weights increased initially and then decreased with increasing daily light integral (DLI) in quadratic funcitons with a highest value under a PFD of 250 μmol m^-2 d^-1. However, no significant differences were observed in fresh and dry weights of hydroponic sweetpotato seedlings grown under PFDs of 200 and 250 μmol m^-2 s^-1. The quantum yield of photosystem II (ФPSII) decreased linearly as DLI increased from 8.6-20.2 mol m^-2 d^-1. Power consumptions based on fresh and dry weights were lowest in sweetpotato seedlings grown under a PFD of 200 μmol m^-2 s^-1 provided by white LEDs with an R:B ratio of 0.9. White LEDs also showed higher light energy use efficiency than white plus red LEDs. In summary, it is recommended that a PFD of 200 μmol m^-2 s^-1 with DLI at 11.5 mol m^-2 d^-1 provided by white LEDs with an R:B ratio of 0.9 is suitable for hydroponic sweetpotato (cv. Beniharuka) seedling production under a controlled environment.

Comparison of blue discoloration in radish root among different varieties and blue pigment stability analysis

The internal blue discoloration of radish root after harvest is a physiological phenomenon that decreases the radish quality. Internal blue discoloration in the roots of 16 varieties of Chinese radish along with the stability of blue pigment under different light, pH, and temperature conditions were investigated. Among the varieties LB05-244 and LB05-240 displayed the greatest degrees of discoloration, while the Piton and Dense radishes exhibited the lowest degrees of discoloration. The light and pH conditions along with the storage temperature affected the pigment stability. The degradation of blue pigment occurred faster under blue light than under green, red, and white light and darkness. Blue pigment degraded fastest at pH values of 13 and 1. The blue pigments in radish exhibited thermal instability, with complete degradation occurring in 5 or 10 min at 90 or 100 °C, respectively. In conclusion, variety affected the discoloration. The pigment exhibited light, pH and thermal instability.

Anthocyanins in Floral Colors: Biosynthesis and Regulation in Chrysanthemum Flowers

Chrysanthemum (Chrysanthemum morifolium) is an economically important ornamental crop across the globe. As floral color is the major factor determining customer selection, manipulation of floral color has been a major objective for breeders. Anthocyanins are one of the main pigments contributing to a broad variety of colors in the ray florets of chrysanthemum. Manipulating petal pigments has resulted in the development of a vast range of floral colors. Although the candidate genes involved in anthocyanin biosynthesis have been well studied, the genetic and transcriptional control of floral color remains unclear. Despite advances in multi-omics technology, these methods remain in their infancy in chrysanthemum, owing to its large complex genome and hexaploidy. Hence, there is a need to further elucidate and better understand the genetic and molecular regulatory mechanisms in chrysanthemum, which can provide a basis for future advances in breeding for novel and diverse floral colors in this commercially beneficial crop. Therefore, this review describes the significance of anthocyanins in chrysanthemum flowers, and the mechanism of anthocyanin biosynthesis under genetic and environmental factors, providing insight into the development of novel colored ray florets. Genetic and molecular regulatory mechanisms that control anthocyanin biosynthesis and the various breeding efforts to modify floral color in chrysanthemum are detailed.

Blue Light Improves Vase Life of Carnation Cut Flowers Through Its Effect on the Antioxidant Defense System

Improving marketability and extension of vase life of cut flowers has practical significance for the development of the cut flower industry. Although considerable efforts have been made over many years to improve the vase life of cut flowers through controlling the immediate environment and through post-harvest use of floral preservatives, the impact of lighting environment on vase life has been largely overlooked. In the current study, the effect of three LED light spectra [white (400-730 nm), blue (peak at 460 nm), and red (peak at 660 nm)] at 150 μmol m-2 s-1 on vase life and on physiological and biochemical characteristics of carnation cut flowers was investigated. Exposure to blue light (BL) considerably delayed senescence and improved vase life over that of flowers exposed to red light (RL) and white light (WL). H2O2 and malondialdehyde (MDA) contents in petals gradually increased during vase life; the increase was lowest in BL-exposed flowers. As a consequence, BL-exposed flowers maintained a higher membrane stability index (MSI) compared to RL- and WL-exposed flowers. A higher activity of antioxidant enzymes [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX)] was detected in petals of BL-exposed flowers, compared to their activities in RL- and WL-exposed flowers. In BL-exposed flowers, the decline in petal carotenoid contents was delayed in comparison to RL- and WL-exposed flowers. Maximum quantum efficiency of photosystem II (Fv/Fm) and a higher percentage of open stomata were observed in leaves of BL-exposed flowers. Sucrose and glucose contents accumulated in petals during vase life; sugar concentrations were higher in BL-exposed flowers than in RL- and WL-exposed flowers. It is concluded that BL exposure improves the vase life of carnation cut flowers through its effect on the antioxidant defense system in petals and on photosynthetic performance in the leaves.

Spectral quality of monochromatic LED affects photosynthetic acclimation to high-intensity sunlight of Chrysanthemum and Spathiphyllum

Vertical farming using light-emitting diode offers potential for the early production phase (few weeks) of young ornamental plants. However, once transferred to the greenhouse, the photosynthetic acclimation of these young plants might depend on this initial light regime. To obtain insight about this acclimatization, Chrysanthemum (sun species) and Spathiphyllum (shade species) were preconditioned in growth chambers for 4 weeks under four light qualities: blue (B), red (R), red/blue (RB, 60% R) and white (W) at 100 μmol m^-2 s^-1 . Monochromatic light (R and B) limited leaf development of both species, which resulted in a lower leaf mass per area when compared to multispectral light (RB for Chrysanthemum, RB and W for Spathiphyllum). R-developed leaves had a lower photosynthetic efficiency in both species. After the light quality pretreatment, plants were transferred to the greenhouse with high-intensity natural light conditions. On the first day of transfer, R and B preconditioned leaves of both species had an inhibited photosynthesis. After 1 week in natural light condition, rapid light curve parameters of Chrysanthemum leaves that developed under B acclimated to sunlight had a similar level than RB-developed leaves unlike R-leaves. Spathiphyllum leaves showed a decrease in maximum electron transport rate and this was most pronounced for the R pretreatment. After 1 month, R-preconditioned Chrysanthemum had the lowest dry mass, while no effects on the dry weight of Spathiphyllum with respect to the pretreatments were observed. Light quality during preconditioning affected the leaf ability to acclimate to natural high light intensities in greenhouse environment.

Light quality affects light harvesting and carbon sequestration during the diel cycle of crassulacean acid metabolism in Phalaenopsis

Crassulacean acid metabolism (CAM) is a specialized photosynthetic pathway present in a variety of genera including many epiphytic orchids. CAM is under circadian control and can be subdivided into four discrete phases during a diel cycle. Inherent to this specific mode of metabolism, carbohydrate availability is a limiting factor for nocturnal CO₂ uptake and biomass production. To evaluate the effects of light quality on the photosynthetic performance and diel changes in carbohydrates during the CAM cycle. Phalaenopsis plants were grown under four different light qualities (red, blue, red + blue and full spectrum white light) at a fluence of 100 µmol m^-2 s^-1 and a photoperiod of 12 h for 8 weeks. In contrast to monochromatic blue light, plants grown under monochromatic red light showed already a significant decline of the quantum efficiency (Φ_PSII) after 5 days and of the maximum quantum yield (F_v/F_m) after 10 days under this treatment. This was also reflected in a compromised chlorophyll and carotenoid content and total diel CO₂ uptake under red light in comparison with monochromatic blue and full spectrum white light. In particular, CO₂ uptake during nocturnal phase I was affected under red illumination resulting in a reduced amount of vacuolar malate. In addition, red light caused the rate of decarboxylation of malate during the day to be consistently lower and malic acid breakdown persisted until 4 h after dusk. Because the intrinsic activity of PEPC was not affected, the restricted availability of storage carbohydrates such as starch was likely to cause these adverse effects under red light. Addition of blue to the red light spectrum restored the diel fluxes of carbohydrates and malate and resulted in a significant enhancement of the daily CO₂ uptake, pigment concentration and biomass formation.

Effects of Artificial Light Treatments on Growth, Mineral Composition, Physiology, and Pigment Concentration in Dieffenbachia maculata “Compacta” Plants

Specific wavebands may allow precise control of plant growth. However, light sources must be carefully evaluated before the large-scale use of supplemental light sources can be implemented. Dieffenbachia maculata “Compacta” plants were grown for 8 weeks in pots in a growth chamber under tightly controlled temperature and humidity in order to assess the effects of supplemental light. Three treatments were applied: (i) using 18-W fluorescent bulbs (T1), (ii) using the same bulbs with supplemental light emitting diodes (LEDs) (Pure Blue and Pure Red Mix-Light-Emitting Diodes (BR-LEDs)) (T2), and (iii) using high-efficiency TL5 fluorescents (T3). Plant biomass, mineral composition, and physiological and photosynthetic parameters were assessed under each light treatment. Total plant dry weight was highest in plants grown under treatments T1 and T3. Other differences were observed between different light treatments, including variation in biomass partitioning as well as N and K concentrations in roots, stems, and leaves. Further, proline and indole 3-acetic acid (IAA) levels were higher in plants grown under the T1 treatment, whereas total soluble sugars and starch were higher in plants grown under treatment T3. Plants grown under treatment T1 had the lowest chlorophyll concentrations. No differences were observed in organ water content and P concentration. T2 was not the best treatment, as expected. The model proposed a linear regression between integrated use of spectral energy (IUSE) and total dry weight (TDW), which showed a good relationship with an R2 value of 0.83. Therefore, we recommend this methodology to discern the effects of the different spectral qualities on plant biomass.

Supplementary Light Source Affects Growth, Metabolism, and Physiology of Adenophora triphylla (Thunb.) A.DC. Seedlings

Adenophora triphylla (Thunb.) A.DC., a well-known herbaceous medicinal species, has been reported to protect against human obesity, cancer, and inflammation. Supplementary lighting is a practical strategy to improve crop quality, especially at a propagation stage. However, there has been no study available on the optimal supplementary light source for the commercial production of A. triphylla seedlings. In this study, plug seedlings were cultivated in a greenhouse for four weeks under an average daily light intensity of 490 μmol·m⁻²·s⁻¹ PPFD coming from the sun and a supplemental lighting (16 h per day) at 120 μmol·m⁻²·s⁻¹ PPFD provided by high pressure sodium (HPS), metal halide (MH), far-red (FR) light, white LED (red: green: blue = 2:4:3, LED-w), or mixed (red: green: blue = 4:1:4) LED (LED-mix). The results showed that LED-mix, with a higher percentage of red and blue light, substantially promoted seedling growth compared to other treatments by increasing stem diameter, biomass, specific leaf weight, and root to shoot ratio. The LED-mix also promoted accumulation of soluble sugar, starch, and chlorophyll in the tissue and increased contents of total phenols and flavonoids. Moreover, stomata density and pore area per leaf area under the LED-mix were remarkably greater than those under other treatments. Furthermore, the Western blot analysis revealed that the expression of photosynthetic protein, D1, was notably enhanced by the LED-mix as compared with other light sources. In addition, the LED-mix alleviated the oxidative damage of seedlings by improving enzymatic and nonenzymatic antioxidant systems. Collectively, these results suggest that the LED-mix was the optimal supplementary light source for the production of highest quality A. triphylla seedlings.

Adventitious rooting of Chrysanthemum is stimulated by a low red:far-red ratio

Adventitious rooting, a critical process in the vegetative propagation of many ornamentals, can be affected by both light intensity and light quality. We investigated the use of spectral light quality to improve adventitious rooting of Chrysanthemum morifolium cuttings by applying different combinations of blue, red and far-red light. Additionally, unrooted cuttings were treated before planting with two auxin transport inhibitors (TIBA and NPA) to study the effect of light quality on auxin biosynthesis and/or transport. Results showed that lowering the R:FR ratio (decreasing the phytochrome photostationary state, PSS) improved rooting significantly and decreased the inhibiting effect of the auxin transport inhibitor NPA. An extra decrease of PSS by adding blue light to a red + far-red spectrum further enhanced rooting. In contrast, adding blue light to solely red light decreased rooting, an effect which was more pronounced in combination with the auxin transport inhibitors TIBA and NPA. Our results show that phytochrome plays a role in adventitious root formation through the action of auxin, but that also blue light receptors interact in this process.

Unravelling the effects of blue light on aerobic methane emissions from canola

It is now well documented that plants produce methane (CH₄) under aerobic conditions. However, the nature of methane production in plants and all the potential precursors and environmental factors that can be involved in the process are not fully understood. Earlier studies have suggested several chemical compounds, including the amino acid methionine, as precursors of aerobic methane in plants, but none have explored other amino acids as potential precursors or blue light as a driving force of methane emission. We examined the effects of blue light, and the promoter or inhibitor of endogenous ethylene on methane and ethylene emissions, amino acids, and some plant physiological parameters in canola (Brassica napus). Plants were grown under four light conditions: no supplemental blue light, and low, medium, or high blue light, and exposed to three chemical treatments: no chemical application, ethylene promoter (kinetin), or ethylene inhibitor (silver nitrate). Regardless of chemical treatment, blue light significantly increased methane emission, which was accompanied by decreased plant biomass, gas exchange, and flavonoids, but by increased wax, and most amino acids. This study revealed that blue light drives aerobic methane emission from plants by releasing of methyl group from a number of amino acids, and that the methane production in plants may have several pathways.