Effect Of Red Light Irradiation Research Articles

Effects of red-light irradiation and melatonininjection on the antioxidant capacity and occurrence of apoptosis in abalones (Haliotis discus hannai) subjected to thermal stress

High ocean temperatures caused by global warming induce oxidative stress in aquatic organisms. Melatonin treatment and irradiation using red light-emitting diodes (LEDs) have been reported to reduce oxidative stress in a few aquatic organisms. However, the effects of red LED irradiation and melatonin injection on the antioxidant capacity and degree of apoptosis in abalones, which are nocturnal organisms, have not yet been reported. In this study, we compared the expression levels of antioxidant enzymes, total antioxidant capacity, and the degree of apoptosis in abalones subjected to red LED irradiation and melatonin treatment. The results revealed that at high water temperatures (25 °C), the mRNA expression levels of the superoxide dismutase (SOD) and glutathione peroxidase (GPx) genes and the antioxidant activity of SOD decreased in abalones in the red-LED irradiated and melatonin-treated groups compared with those in abalones in the control group. Although high water temperatures induced DNA damage in the abalone samples, the degree of apoptosis was lower in the red-LED irradiated and melatonin-treated groups than in the control group. Overall, the abalones in the melatonin-treated and red-LED irradiated groups showed reduced oxidative stress and increased antioxidant enzyme levels under thermal stress compared with those in the control group. Therefore, red LED irradiation is a promising alternative to melatonin treatment, which is difficult to administer continuously for a long time, for protecting abalones from oxidative stress.

Combination effect of red light irradiation and Traychspermum ammi essential oil on colorectal cancer cells (SW480).

Colon cancer is the third significant reason for death related to cancers in the world. There are various treatments for colon cancer, which have several side effects. Polyphenol agents are a type of antioxidant in plants that have diverse biological properties, such as anti-cancer effects. Here, we investigate the effect of Trachyspermum ammi essential oil (TEO) and red light irradiation on the colorectal cancer cell line (SW 480). The colorectal cancer cell lines were irradiated at 660nm for 90s and then the cells were incubated with different TEO concentrations. In another study, cells initially were treated with various TEO concentrations and then irradiation for 90s. Effect of TEO and the red light irradiation on viability of the cell, ROS generation, and cell cycle was assessed by MTT and flow cytometry, respectively. The findings demonstrated that early incubation with TEO and then irradiation decreased the SW 480 cells survival more than the early irradiation at 660nm and then essential oil. In addition, TEO treatment at IC50 concentration in combination with low-level laser irradiation induces ROS generation in SW 480 cells as compared to the dark group. In addition, TEO treatment at IC50 in combination with low-level laser irradiation induces G0/G1 arrest of the cell cycle in SW 480 cells in comparison to the dark group. This study revealed that the Trachyspermum ammi essential oil in combination with low-level laser results in more reduction in survival which leads to ROS generation and cell cycle arrest in SW 480 colorectal cancer cells.

Effect of postharvest irradiation with red light on epidermal color and carotenoid concentration in different parts of tomatoes

The aim of this study was to investigate the effect of red light irradiation during postharvest ripening with focus on the outer (epicarp and mesocarp) and inner (endocarp and seed) parts of tomatoes by evaluating concomitant alterations in bioactive compounds, such as lycopene, β-carotene, total phenolic and total flavonoid concentrations, external fruit color and spectral reflectance pattern, and the Simple Chlorophyll Fluorescence ratio. As promising measure, deriving from previous studies, green stage-1 tomatoes were harvested and treated daily with red light for 12 h per day, for 15 days (followed by storage in darkness for additional 6 days) or continuously radiated with red light for 21 days. Control untreated tomatoes were kept in the dark for the same period. Application of continous red light strongly accelerated changes in the outer layer of fruit, for example visible in color parameters. Significant differences between treatments were analyzed for major secondary metabolite compounds such as lycopene, β-carotene, total phenolic and total flavonoid in both outer and inner fruit layers. Continuous red light treatment led to the highest concentration of secondary metabolite compounds in all parameters. Therefore, it can be concluded that continuous red light radiation is the most effective treatment to accelerate the color development and ripening of the outer layer of the epicarp. Furthermore, it plays a role in stimulating the inner layer of the endocarp to provide beneficial secondary metabolite compounds.

The Effects of Red-light Irradiation and a Reflective Sheet Cover on the Population Density of Two Thrips Species（Thysanoptera: Thripidae）on Eggplant and Cucumber in a Greenhouse

The effects of red-light irradiation and a reflective sheet cover on the population density of two thrips species（Thysanoptera: Thripidae）, the melon thrips（Thrips palmi Karny）and the onion thrips（Thrips tabaci Lindeman）, were investigated on eggplant and cucumber in a greenhouse in 2014 and 2015. Red fluorescent lamps were illuminated from above the plants and a light reflecting sheet was placed on the ridges of the treated plots. A greenhouse without either material was set up as a control plot. The population densities of the two thrips species on eggplant and T. palmi on cucumber were significantly lower in the treated plots than in the control plot.

Effects of red-light irradiation on the function and survival of fresh and liquid-stored donkey semen

This study sought to determine whether sperm irradiation using a light emission diode (LED) at 620–630 nm affects the motility, membrane integrity (viability), mitochondrial activity and intracellular levels of reactive oxygen species (ROS) in fresh diluted and liquid-stored donkey semen. With this purpose, sixteen ejaculates (eight fresh diluted and eight cooled-stored) were collected from eight adult jackasses. Fresh semen samples were diluted in Kenney extender and stimulated with red-light after collection, whereas cooled semen was stored at 4 °C for 24 h after dilution and then irradiated. In all cases, semen samples were packed into 0.5-mL transparent straws, which were then randomly divided into control and 19 treatments: six consisted of single red-light exposure, and the other 13 involved irradiation at light-dark-light intervals. Upon irradiation, sperm motility, membrane integrity mitochondrial membrane potential (MMP) and intracellular levels of superoxide anion (·O2−) and hydrogen peroxide (H2O2) were evaluated. While specific light-patterns increased both sperm motility and mitochondrial activity, they did not affect sperm membrane integrity and had no clear impact on intracellular ROS levels. The effects of irradiation patterns differed between fresh and cooled semen since, whereas 1 and 4 min patterns induced the greatest increments in the total and progressive motility of fresh semen, 4 min, 4-1-4 and 4-4-4 were the most suitable for cooled-stored samples. In both fresh diluted and cooled-stored semen, the motility increase observed after light-stimulation for 4 min was concomitant with changes in the percentages of spermatozoa with high mitochondrial membrane potential. In summary, this study shows, for the first time, that specific irradiation patterns increase sperm motility and mitochondrial activity in the donkey. Furthermore, the precise effect of red-light appears to depend on the specific functional status of cells, with separate effects on fresh and cooled samples.

The effect of red light (660 nm) on proliferative activity and growth reactions in seedlings of plants with contrast photoperiodic reaction

The results of a study of the effect of red light irradiation (660 nm) on the proliferative activity of root meristems and growth reactions of plant seedlings with contrast photoperiodic reactions are presented in this paper. Plants of the family Fabaceae contrasting in the photoperiodic reaction were used as plant material: long-day plants (LDP) of peas (Pisum sativum L.) of the Metsenat variety and short-day plants (SDP) of soybean (Glycine max (L.) Merr.) of the Korsak variety. Phytochromes were activated by irradiating the aerial part of the experimental seedlings with monochromatic red light (RL) of 660 nm using an LED matrix for 30 minutes for 5 days. The proliferative activity of meristem cells was determined by analysis of the mitotic index (MI). The growth reaction was studied by linear growth indicators: the total length of the seedling, the length of the aerial part and roots, and the integral indicator of growth and biosynthetic processes – the accumulation of biomass. According to the results of the experiments, it was shown that the mitotic activity of root meristems under the influence of red light on the aerial part in seedlings of the LDP of pea Metsenat decreased slightly – by 8 %, and in the seedlings of the SDP of soybean Korsak increased significantly – by 47 %. The linear growth and accumulation of biomass in the aerial part under the action of RL irradiation in seedlings of pea of the Metsenat variety and soybean of the Korsak variety decreased, and this effect was more pronounced in soybean than in pea. During irradiation of RL the linear root growth and their biomass accumulation in seedlings of LDP pea decreased slightly, while at the same time, these processes in the roots of soybean SDP seedlings were significantly stimulated. Under the influence of RL in pea seedlings, the growth rate did not change in the length of the aerial part, but in the roots increased, while the rate of biomass accumulation by them decreased. In soybean seedlings during RL irradiation, the growth rate of both the aerial part and the roots decreased, the biomass accumulation rate by the aerial part increased, and by the roots – decreased. LDP of pea Metsenat and SDP of soybean Korsak variety differ in the nature of the reaction of growth processes in response to irradiation of RL. The activation of the phytochrome system in the aerial part causes changes in the proliferative activity and growth processes of the roots, which indicate a systemic response of the plant organism to the action of this factor. The relationship of the photoperiodic reaction of plants with the realization of phytochrome signal in the plant by activating or inhibiting the proliferative activity of root meristems and growth reactions is discussed.

The effect of red light irradiation on the proliferation of mesenchymal stem cells

Objective To study the effect of red light on the proliferation of mesenchymal stem cells (BMSCs). Methods BMSCs were isolated from Sprague-Dawley rats and cultured in vitro. They were irradiated with red light delivered by a light-emitting diode placed 2 cm above the cell layer. The light had a wavelength of 620 nm and a maximum power of 1 W. The measured optical power density was 6.67 mW/cm2. The cells were randomly divided into a control group and three experimental groups. The control group was not irradiated, while the other 3 groups were irradiated at 0.5, 1 and 2 J/cm2 for 75 s, 150 s or 300 s, repeated twice with an interval of 12 hours. Forty-eight hours after the irradiation, cellular proliferation was evaluated using CCK-8 assays and DNA replication was quantified with a Cell-Light EdU. Changes in the cell cycle parameters were detected using flow cytometry. Results After the irradiation, the proliferation and DNA replication of the experimental group were significantly strengthened, while the cell growth cycle was significantly shortened compared with the control group, especially in the group irradiated at 0.5 J/cm2. Conclusion Low-energy red light irradiation can promote the proliferation of mesenchymal stem cells in vitro by enhancing DNA replication and shortening the cell growth cycle. Key words: Low-energy phototherapy; Light-emitting diodes; Photobiomodulation; Mesenchymal stem cells; Proliferation

Red light-emitting diode irradiation regulates oxidative stress and inflammation through SPHK1/NF-κB activation in human keratinocytes

Oxidative stress, in which the amount of oxidants exceeds the capacity of antioxidant defense system, is a well-accepted pathogenesis of several human diseases. Light-emitting diode irradiation (LEDI) is an efficient strategy to counteract this condition. The biological effect of phototherapy, using visible light, has attracted recent attention especially in dermatological practice. However, little is known about the molecular mechanism of the anti-oxidant and anti-inflammatory effects of red light irradiation. We evaluated these effects of LEDI in HaCaT human keratinocyte cells under phorbol-12-myristate-13-acetate (PMA) induced reactive oxygen species (ROS). Microarray analysis revealed changes in 309 genes after LEDI. LEDI at 625 nm produced ROS scavenging and anti-inflammatory effects. One of the most important genes identified by microarray analysis was sphingosine kinase-1 (SPHK1), which is a key molecule in sphingolipid metabolism. SPHK1 knock-down drastically reduced ROS scavenging efficiency as well as expression levels of inflammation-related proteins in PMA-treated HaCaT cells. These results not only indicate the potential for the clinical application of 625-nm LEDI in treating skin disorders via ROS and/or inflammation, but also suggest SPHK1 as a potential therapeutic target in phototherapy.

Effects of red light irradiation on blood phosphorus in maintenance hemodialysis patients

Objective To evaluate the effect of red light irradiation on serum phosphorus reduction in hemodialysis. Methods Sixty maintenance hemodialysis patients were divided into treatment group and control group. During the hemodialysis, the blood in the extracorporeal circulation tube of the patents in the treatment group was irradiated with red light by a MRX-1 red light therapy system. The irradiation was continued for 60 minutes each time, and one course of the treatment contained 10 times of irradiations. Patients in the control group were subjected to hemodialysis by conventional methods. The serum phosphate levels of all patients were measured before and after the treatment. Results The symptoms of dialysis disequilibrium of the patients in the treatment group were alleviated. There was no significant difference in serum phosphate levels between the treatment group and the control group before hemodialysis, while a statistically significant difference was found after the treatment (P<0.05). Conclusions Hemodialysis combined with red light irradiation on external blood trails can contribute to the decrease of serum phosphate levels in maintenance hemodialysis patients. Key words: Red light irradiation; Maintenance hemodialysis; Serum phosphate

Effects of 630 nm Red and 460 nm Blue Light Emitting Diode Irradiation on Healing of the Skin Wound in Japanese Big-ear White Rabbit.

Objective To observe the effects of 630 nm red light and 460 nm blue light emitting diode irradiation on the healing of skin wounds in Japanese big-ear white rabbits. Methods The skin wound model was established with 8 Japanese big-ear white rabbits. Three parts of vulnus in each rabbit were used:two parts of vulnus were irradiated vertically by red and blue LED light,respectively(15 min/time),and the distance between lights and wounds was 15 cm;the 3rd part of the wound was used as a control. On the 21st day of the wounds exposure to light,the number of healing wounds and the percentage of healing area were recorded and the treatment effect of these two light sources was compared. HE staining was used to analyze the newborn tissue structure. Masson staining was used to observe the proliferation of skin collagen fibers. Immuohistochemical staining was used to analyze fibroblast growth factor(FGF),epidermal growth factor(EGF),endothelial growth factor(CD31),proliferating cell nuclear antigen(Ki-67),and inflammatory cytokines(CD68)infiltration in the skin. Results The healing rate in the red light,blue light,and control groups was 50.0%(4/8),25.0%(2/8),and 12.5%(1/8),respectively. Since the 12th day after modeling,the healing area percentage in the red light group was significantly higher than those in the blue light and control groups(P<0.05,P<0.01). On the 21st day after modeling,the skin thickness of the red light group was(2.95±0.34)mm,which was significantly higher than that in control group [(2.52±0.42)mm;F=3.182,P=0.016)]. The average optical density of collagen fibers was 0.15±0.03 in red light group,which was significantly higher than that of the blue light group(0.09±0.01;F=7.316,P=0.012)and control(0.07±0.01;F=7.316,P=0.003). The results of immunohistochemistry showed the expression levels of EGF,FGF,CD31 antigen,and Ki-67 in the red light group were significantly higher than those in the blue light and control groups,whereas the CD68 expression was significantly lower(P<0.05 or P<0.01). Conclusion LED red light irradiation can promote the healing of skin wounds in Japanese big-ear white rabbits,which may be achieved by the effect of red light irradiation in stimulating the proliferation of skin epidermal cells,vascular endothelial cells,and fiberous tissue.

Laser Biostimulation

Photomedicine and Laser SurgeryVol. 31, No. 6 Guest EditorialLaser BiostimulationAdam MesterAdam MesterSearch for more papers by this authorPublished Online:6 Jun 2013https://doi.org/10.1089/pho.2013.9876AboutSectionsView articleView Full TextPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View articleFiguresReferencesRelatedDetailsCited byShort-Term Efficacy of High-Intensity Laser Therapy in Alleviating Pain in Patients with Knee Osteoarthritis: A Single-Blind Randomised Controlled TrialPain Research and Management, Vol. 2022Medical Applications of Diode Lasers: Pulsed versus Continuous Wave (cw) Regime17 June 2021 | Micromachines, Vol. 12, No. 6Effect of Laser Irradiation on Cell Cycle and Mitosis17 September 2018 | Journal of Lasers in Medical Sciences, Vol. 9, No. 4Low level laser therapy reduces oral leukoplakia lesion size: Results from a preliminary studyOral OncologyShould open excisions and sutured incisions be treated differently? A review and meta-analysis of animal wound models following low-level laser therapy30 March 2018 | Lasers in Medical Science, Vol. 33, No. 6Preconditioning With Low-Level Laser Irradiation Enhances the Therapeutic Potential of Human Adipose-derived Stem Cells in a Mouse Model of Photoaged Skin21 April 2018 | Photochemistry and Photobiology, Vol. 94, No. 4Approach and potentiality of low level laser therapy in veterinary medicineMechanisms and Mitochondrial Redox Signaling in Photobiomodulation19 January 2018 | Photochemistry and Photobiology, Vol. 94, No. 2The influence of experimental conditions on the final result of photoinhibition of Staphylococcus aureusPhotodiagnosis and Photodynamic Therapy, Vol. 19Apoptosis induced by low-level laser in polymorphonuclear cells of acute joint inflammation: comparative analysis of two energy densities5 April 2017 | Lasers in Medical Science, Vol. 32, No. 5Penetration depth of photons in biological tissues from hyperspectral imaging in shortwave infrared in transmission and reflection geometriesJournal of Biomedical Optics, Vol. 21, No. 12The effect of red light irradiation on spermatozoa DNADifferent Photoresponses of Microorganisms: From Bioinhibition to Biostimulation8 January 2016 | Current Microbiology, Vol. 72, No. 4Comparative effects of two different doses of low-level laser therapy on wound healing third-degree burns in rats8 February 2016 | Microscopy Research and Technique, Vol. 79, No. 4Radiation absorption in different kinds of tissue analysis: ex vivo study with supercontinuum laser sourceLight Effect on Water Viscosity: Implication for ATP Biosynthesis8 July 2015 | Scientific Reports, Vol. 5, No. 1A Comparative Study of the Effectiveness of Immediate Versus Delayed Photobiomodulation Therapy in Reducing the Severity of Postoperative Inflammatory Complications2 September 2015 | Photomedicine and Laser Surgery, Vol. 33, No. 9Low-intensity infrared laser effects on zymosan-induced articular inflammatory responseBiophotonic effect of diode laser irradiance on tensile strength of diabetic rats16 October 2014 | Journal of Cosmetic and Laser Therapy, Vol. 17, No. 2Combined Central and Peripheral Stimulation for Treatment of Chronic Tinnitus15 July 2014 | Neurorehabilitation and Neural Repair, Vol. 29, No. 3Adjunctive use of combination of super-pulsed laser and light-emitting diodes phototherapy on nonspecific knee pain: double-blinded randomized placebo-controlled trial21 May 2014 | Lasers in Medical Science, Vol. 29, No. 6Light Pumping Energy Into Blood Mitochondria: A New Trend Against Depression?10 February 2014 | Photomedicine and Laser Surgery, Vol. 32, No. 2The Current Status of LLLT in the Field of Dental and Oral Surgery -In Anticipation of the Recent Trend and the Concept of LLLT-Nippon Laser Igakkaishi, Vol. 34, No. 4The use of physiotherapy tools in medical treatment. The use of heat, light, electric, magnetic, ultrasound and shock wave therapy as well as medical massage in Hungarian medical practiceOrvosi Hetilap, Vol. 154, No. 48 Volume 31Issue 6Jun 2013 InformationCopyright 2013, Mary Ann Liebert, Inc.To cite this article:Adam Mester.Laser Biostimulation.Photomedicine and Laser Surgery.Jun 2013.237-239.http://doi.org/10.1089/pho.2013.9876Published in Volume: 31 Issue 6: June 6, 2013PDF download

Nitrergic Response to Clostridium perfringens Infection in the Rat Brain Regions Effect of Red Light Irradiation

A single intraperitoneal injection of a gram-positive pathogen Clostridium perfringens (Cp) causes a remarkable down-regulation the constitutive nitric oxide synthase (cNOS) with a simultaneous increase in the activity of inducible NOS (iNOS) and the level of reactive nitrogen species in the rat brain major regions (cortex, striatum, hippocampus and hypothalamus) at 48 h post-administration of Cp. Treatment by both a semiconductor laser (SCL) and/or a light-emitting diode (LED) with same wavelength, energy density and time exposure (continuous wave, λ=654 nm, fluence=1.27 J/cm(2), time exposure=600 s) could modulate brain nitrergic response following Cp-infection. Besides, unlike the LED, the SCL-irradiation prevents the cNOS inhibition in all the studied brain regions and might be useful in restoring its function in neurotransmission and cerebral blood flow, along with providing a protective effect against nitrosative stress-induced iNOS-mediated injury in the brain regions.

Suppression by Red Light Irradiation of Corynespora Leaf Spot of Cucumber Caused byCorynespora cassiicola

The effect of red light irradiation on development of Corynespora leaf spot of cucumber plants (Cucumis sativus L. cv. Hokushin) caused by Corynespora cassiicola (Berk. & Court.) was investigated in greenhouses. In a greenhouse without red light (―Red), lesions enlarged, coalesced, and finally covered the entire leaves of cucumber. In a greenhouse with red light (+Red), however, lesion appearance was delayed relative to that under ―Red and its development was also significantly suppressed. Such difference in disease development was also observed in cucumbers grown under +Red and ―Red in the same greenhouse. Disease suppression under red light was also observed in glasshouse-grown C. cassiicola-inoculated cucumbers. Red light did not inhibit the infection behaviour of the pathogen. Our results indicated that the delay and suppression of Corynespora leaf spot of cucumber under + Red were due to induction of resistance in cucumber, and not to differences in environmental conditions or fungal population between the two greenhouses. Red light-induced resistance might contribute to the development of new methods for controlling Corynespora leaf spot of greenhouse-grown cucumber.

Combined effect of low-power laser irradiation and anthraquinone anticancer drug aclarubicin on survival of immortalized cells: Comparison with mitoxantrone

The photodynamic response of the anthraquinone anticancer drug aclarubicin (ACL) was investigated in vitro and compared with that of mitoxantrone (MTX). Cultured immortalized rodent B14 and NIH 3T3 cells were used in the experiments as a model for cells with neoplastic phenotype. Long-term cytotoxicity and inhibition of cell proliferation assayed by the clonal growth and MTT-tetrazolium methods were estimated to compare the efficacy of aclarubicin and mitoxantrone in photosensitizing cells and their death after non-thermal exposure to monochromatic laser light. Green He-Ne (543.5 nm) or red semiconductor (670 nm) low-power laser (LPL) irradiations were applied. Different dose-responses of both cell lines to aclarubicin and mitoxantrone were found so that the cytotoxicity of MTX was considerably greater than the cytotoxicity of ACL. Phototherapy response (P < 0.0001) was observed only for B14 cells after sensitisation with aclarubicin. Under the same conditions no significant effect of red light irradiation (semiconductor 670 nm laser) on survival of both cell lines treated with mitoxantrone was found.

Gene expression of fibroblasts following light irradiation

Gene expression of fibroblasts following light irradiation

CDNA Microarray Analysis of Gene Expression Profiles in Human Fibroblast Cells Irradiated with Red Light

In this paper, the cDNA microarray technique was used to investigate the gene expression profiles of human fibroblasts irradiated by low-intensity red light. Proliferation assays showed that the fibroblast HS27 cells responded with a curve effect to different doses of low-intensity red light irradiation at a wavelength of 628 nm. An optimal dose of 0.88 J per cm2 was chosen for subsequent cDNA microarray experiments. The gene expression profiles revealed that 111 genes were regulated by the red light irradiation and can be grouped into 10 functional categories. Most of these genes directly or indirectly play roles in the enhancement of cell proliferation and the suppression of apoptosis. Two signaling pathways, the p38 mitogen-activated protein kinase signaling pathway and the platelet-derived growth factor signaling pathway, were found to be involved in cell growth induced by irradiation of low-intensity red light. Several genes related to antioxidation and mitochondria energy metabolism were also found to express differentially upon irradiation. This study provides insight into the molecular mechanisms associated with the beneficial effects of red light irradiation in accelerating wound healing.

Role of Calcium in Phytochrome-Controlled Nyctinastic Movements of Albizzia lophantha Leaflets

The involvement of Ca(2+) on phytochrome-controlled nyctinastic closure in Albizzia lophantha has been studied by testing the effect of the calcium ionophore 6S-[6alpha(2S(*),3S(*)),8beta(R(*)),9beta,11alpha]-5- methyl-amino)-2-[[3,9,11-trimethyl-8-[-1-methyl-2-oxo-2-(1H-pyrrol-2-yl) ethyl]-1,7-dioxaspiro[5.5]-undec-2yl] methyl]-4-benzoxazolecarboxylic acid (A23187) and the intracellular calcium antagonist 8-(diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8). An external supply of Ca(2+) or calcium ionophore A23187 to the Albizzia leaflets emulates the effect of red light irradiation and counteracts the inhibitory effect of far red light. The intracellular calcium antagonist TMB-8 supplied to Albizzia leaflets inhibits the effect of red light, but had no effect on far red irradiated plants. This suggests a dependence between phytochrome action and intracellular free Ca(2+). We suggest that calcium acts as a phytochrome messenger on control of ion fluxes that drive turgor changes in pulvinular motor cells.