Growth and Dormancy in Lunularia cruciata (L.) Dum: VI. GROWTH REGULATION BY DAYLENGTH, BY RED, FAR-RED, AND BLUE LIGHT, AND BY APPLIED GROWTH REGULATORS AND CHELATING AGENTS

Experiments with photoperiods ranging from 2 to 24 h confirmthat 8 h light per day is optimal for Lunularia: there is nogrowth in the dark or in continuous light, which causes therapid onset of dormancy. Short-day cycles intercalated amonga series of continuous light cycles promote growth; in cycleslonger than 24 h very long dark periods are detrimental. Withvery short photoperiods (5 min) red light promotes growth moreeffectively than white light at higher intensity; far-red actsas dark. The growth effects of red and far-red light breaks(3 min) depended on the time of application; red light inhibitedin the middle but promoted at the beginning of the 16-h darkperiod of a short day; far-red light had the opposite effect;in each case red and far-red effects were reversible by theother wavelength. Blue light gave the same response as red includingthe reversibility of far-red effects and vice versa. Surprisingly,significant effects of 5 min red, blue, and far-red irradiationwere also found in the middle of the main high-intensity white-lightperiod, red and blue promoting growth, far-red reducing it;again there was ready reversibility of the effects. Growth promoters of higher plants are generally inhibitory toLunularia or have little effect; among growth retardants TIBA,Phosphon D, and CCC gave a slight promotion of growth. EDTApromoted growth (cell numbers) very significantly while 8-hydroxyquinolinewas initially inhibitory, but had a marked latent promotingeffect when subsequently washed from the thalli.     

The Light-Growth Response of Vaucheria. A conditio sine qua non of the Phototropic Response?

This is the first report of a positive light-growth response(LGR) in tip-growing cells. Tip-growth of a coenocytic fresh-wateralga Vaucheria terrestris was temporarily accelerated by a shortpulse of blue light. The LGR occurred after a lag period shorterthan 1 min, and reached its maximum ca. 3 min after the onsetof blue light. The growth rate then rapidly decreased againand often showed a damped oscillation with a period of about10 min. If the blue light pulse was shorter than 2 min, themagnitude of the LGR seemed to obey the reciprocity law. Anothertype of growth promotion, the apical expansion, is brought aboutwhen the pulse is longer than 5 min. In this report, however,only the LGR which is caused by a short pulse of blue light,is dealt with. The threshold fluence at 456 nm was ca. 10 Jm^–2 at pH 7.0. The response was very sensitive to thepH of the medium: it was 5 J m ^–2 at pH 7.5, 150 J m^–2at pH 6, and 750 J m^–2 at pH 5. The phototropic responsealso showed a very similar pH-dependency between pH 5.5 andpH 6.5. The relationship between the positive LGR and positivephototropic response was found to be much closer in this tip-growingalga than in diffuse-growing cells. The possibility that theLGR is the primary and essential process preceeding the phototropicresponse is discussed.     

Red and blue light-stimulated proton efflux by epidermal leaf cells of the Argenteum mutant of Pisum sativum

Light stimulates leaf expansion in dicotyledons by increasingapoplastic acidification, cell wall loosening and solute accumulationfor turgor maintenance. Red and blue light enhance growth viadifferent photo-systems, but the cellular location and modesof action of these systems is not known. Here, the effect of red and blue light was studied on transportprocesses in epidermal cells of expanding leaves of the Argenteummutant of Pisum satlvum. Both red and blue light caused extraceiiuiaracidification by isolated epidermal tissue, which was stimulatedby extracellular K⁺ and inhibited by DCCD at 0.1 mol m^–3.Acidification induced by red compared with blue light showeddifferent saturating kinetics in fluence rate-response curves.Under near saturating light conditions the effects of red andblue light were additive. The red light-induced acidificationwas inhibited by far-red light while the blue light-inducedacidification was not. Light caused a hyperpoianzation of themembrane potential in epidermal strips, and stimulated ⁸⁶Rb⁺uptake by epidermal protoplasts. These results show that phytochromeand an additional blue light-photoreceptor function in isolatedepidermal cells to promote proton efflux, hyperpolarization,and cation uptake. Key words: Pisum sativum, light-induced acidification, ion transport, epidermis, photoreceptor     

Effects of Light on Chlorophyll Formation in Cultured Tobacco Cells I. Chlorophyll Accumulation and Phototransformation of Protochlorophyll(ide) in Callus Cells under Blue and Red light

A marked accumulation of chlorophyll was observed in calluscells of Nicotiana glutinosa when they were grown under bluelight, while under strong red light no chlorophyll accumulated.This blue light effect saturated at an intensity of about 500mW.m^–2. The effects of white, blue and red light on the transformationof protochlorophyll (ide) (Pchl) accumulated in dark-grown calluscells were studied by following the changes in the intensityof fluorescence emitted by Pchl and different forms of chlorophyll(ide) (Chi). Pchl with a fluorescence maximum at 633 nm (absorptionmaximum: 630 nm) decreased slowly, concomitant with an increasein Chl having a fluorescence maximum at 677 nm (absorption maximum:675 nm), which was subsequently transformed, independently oflight, to Chi with a fluorescence maximum at 683 nm (absorptionmaximum: 680 nm). Both blue and red light of low intensitieswere effective for the phototransformation, while red light,but not blue light, of high intensities caused significant destructionof Pchl. An action spectrum for this photodestruction showedthat the maximum destruction took place at 630 nm. White lightof high intensities was effective for the photoreduction withonly slight destruction of Pchl, suggesting that blue lightcounteracts the destructive effect of red light. At low temperatures,however, blue light as well as red light of low intensitiescaused photodestruction of Pchl. It was inferred that blue lightenhances a certain step or steps involved in the productionof a reductant required for the photoreduction of Pchl to Chl. (Received July 3, 1981; Accepted November 11, 1981)     

Action Spectrum for Light-induced Chloroplast Accumulation in a Marine Coenocytic Green Alga, Bryopsis plumosa

A marine coenocytic green alga, Bryopsis plumosa exhibited multistriatetype protoplasmic streaming of a velocity less than 100 µm.min^–1.When the alga was illuminated locally, chloroplasts and othercell organelles accumulated in the illuminated zone. The actionspectrum for this reaction showed that blue light between 380and 500 nm was most effective. The velocity of chloroplast movement decreased when the cellwas totally illuminated with blue light, but no comparable changewas observed under red light illumination. Therefore, chloroplastaccumulation probably was caused by the reduced streaming ratein the illuminated zone. Electron microscopy showed cytoplasmic microtubules arrangedparallel to the cell axis in the vicinity of the chloroplasts.Chloroplast movement was inhibited heavily by treatment withantimicrotubule agents, but was little affected by cytochalasinB at a concentration of 10 µg/ml. (Received May 30, 1981; Accepted August 24, 1981)     

Effects of microbeam light on growth and phototropism ofPilobolus crystallinus sporangiophores

A small blue-light beam (50 μm in diam) was used to examine light-growth response and phototropism inPilobolus crystallinus sporangiophores. Continuous irradiation by microbeam of a region 100–150 μm from the apex promoted the growth of a dark-adapted sporangiophore for about 15 min after a lag period of 1–2 min. After the promotion, the growth rate fell below that before the irradiation. Irradiation of the apex of sporangiophore slightly promoted the growth but strongly inhibited the growth after the promotion. A smaller light beam (10 μm in diam) applied continuously at grazing incidence along one side of the sporangiophore caused bending toward the shaded side, implying that the irradiated side grew more rapidly than the shaded side and that the lens effect is involved in the phototropism of young sporangiophores ofP. crystallinus. The involvement of the lens effect was confirmed by the fact that a carotenoid-less mutant was 1.5–2 times more sensitive to unilateral blue light than the wild type, probably because of a smaller intracellular light attenuation during passage through the mutant cell.     

The Influence of Chlorophyll on the Spectral Control of Elongation Growth in Chenopodium rubrum L. Hypocotyls

The inhibitory effectiveness of various monochromatic wavelengthsbetween 399 and 802 nm on hypocotyl elongation growth in light-grownChenopodium rubrum L. seedlings has been studied. The responsesof normal light-grown seedlings and chlorophyll-free light-grownseedlings were compared. Both types of seedling responded moststrongly to the blue and red waveband although a distinct peakof red light effectiveness was not observed in normal greenseedlings. The presence of chlorophyll also correlates witha lower inhibitory effectiveness of most wavelengths in the400–700 nm waveband. Photon fluence-rate response curves were not parallel; whereasthe plants were very sensitive to changes in fluence-rate inthe blue waveband, a much less marked fluence-rate dependencywas observed in the red and far-red wavebands. (Received September 10, 1981; Accepted April 26, 1982)     

Effects of Colchicine and Light on Cell Form in Fern Gametophytes. Implications for a Mechanism of Light-induced Cell Elongation

Spores of the fern, Onoclea sensihilis L., suffer a disruption of normal development when they are cultured on media containing colchicine. Cell division is inhibited, and the spores develop into giant spherical cells under continuous white fluorescent light. In darkness only slight cell expansion occurs. Spherical cell expansion in the light requires continuous irradiation. Photosynthesis does not seem to be involved, since variations in light intensity do not affect the final cell diameter; the addition of sucrose to the medium does not permit cell expansion in darkness; and the inhibitor DCMU does not block the light-induced cell expansion. Continuous irradiation of colchicine-treated spores with blue, red or far-red light produces different patterns of cell expansion. Blue light permits spherical growth, similar to that found under white light, whereas red and far-red light promote the reestablishment of polarized filamentous growth. Although ethylene is unable to induce polarized cell expansion in colchicine-treated spores in darkness or white and blue light, it enhances filamentous growth which already is established by red or far-red irradiation. Both red and far-red light increase the elongation of normal filaments (untreated with colchicine) above that of dark-grown plants, but under all 3 conditions the rates of volume growth are identical. Light, however, does cause a decrease in the cell diameters of irradiated filaments. These data are used to construct an hypothesis to explain the promotion of cell elongation in fern protonemata by red and far-red light. The model proposes light-mediated changes in microtubular orientation and cell wall structure which lead to restriction of lateral cell expansion and enhanced elongation growth.     

Stimulation of growth and ion uptake in bean leaves by red and blue light

Red and blue light both stimulate growth and ion accumulation in bean (Phaseolus vulgaris L.) leaves, and previous studies showed that the growth response is mediated by phytochrome and a blue-light receptor. Results of this study confirm that there is an additional photosynthetic contribution from the growing cells that supports ion uptake and growth. Disc expansion in the light was enhanced by exogenous K⁺ and Rb⁺, but was not specific for anions. Light increased K⁺ accumulation and the rate of ⁸⁶Rb⁺ uptake by discs, over darkness, with no effect of light quality. The photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, inhibited light-driven ⁸⁶Rb⁺ uptake by 75%. Light quality caused differences in short-term kinetics of growth and acidification of the leaf surface. At comparable fluence rates (50 μmol m⁻² s⁻¹), continuous exposure to blue light increased the growth rate 3-fold after a 2-min lag, whereas red light caused a smaller growth response after a lag of 12 min. In contrast, the acidification of the leaf surface normally associated with growth was stimulated 3-fold by red light but only slightly (1.3-fold) by blue light. This result shows that, in addition to acidification caused by red light, a second mechanism specifically stimulated by blue light is normally functioning in light-driven leaf growth.     

Intracellular Photoreceptive Site for Polarotropism in Protonema of the Fern Adiantum capillus-veneris L.

Polarotropic response was induced by short-term irradiationwith polarized red light in single-celled protonemata of thefern Adiantum capillus-veneris L. that had been grown apicallyunder red light for 6 days then for 15 hr in the dark. Sequentialobservation of the apical growth with a time-lapse video systemshowed that the direction of apical growth changed within 30min after the brief irradiation. Microbeam irradiation withpolarized red light of the subapical, dark-grown flank of theapical, 5–15 µm region of the protonema inducedthe polarotropic response most effectively. When both sidesof the flank were irradiated simultaneously with different fluencesof polarized red light with the same vibrating plane of 45°with protonemal axis, polarotropism took place normally, ifthe fluence ratio, B/A (B: fluence given to the side towardwhich the protonema should bend in polarotropism, A: fluencegiven to the other side) was not less than one-half. But, ifthe ratio became less than that, the protonemata no longer showedpolarotropism, they grew toward the side of higher fluence dependingon the difference in fluences between both sides. (Received August 1, 1981; Accepted September 29, 1981)     

Oak Seedlings Grown in Different Light Qualities

Seedlings of oak (Quercus robur) were germinated in darkness for 3 weeks and then given continuous light or short pulses of light (5–8 min every day). The morphological development was followed during 25 days. In continuous white, blue, and red light the stem growth terminated after about 10 days by formation of a resting bud. At that time the seedlings were about 100 mm high. In con tinuous long wavelength farred light (wavelength longer than 700 nm) the stem growth including leaf formation was continuous without the formation of resting buds, and the stem length was about 270 mm after 25 days. The number of nodes developed became twice that of the seedlings grown in while light. The leaves became well developed in all light colours, but leaf areas were largest in plants cultivated in white light. Compared to dark grown seedlings the mean area per leaf was increased about five times in continuous long wavelength far red light. A supplement with short (5 min) pulses of red light each day increased the leaf area up to 20 times. The stem elongation showed a high energy reaction response, i.e. the stem length increased only in continuous long wavelength far-red light but was not influenced by short pulses of red light or far-red light. The leaf expansion, however, was increased by short pulses of red light with a partial reversion of the effect by a subsequent pulse of far-red light. The fraction of the plant covered with periderm was higher in plants given continuous light. In respect to periderm inhibition continuous long wavelength far red light was the most effective. The transfer of seedlings from darkness to continuous white light gave anthocyanin formation in the stem 10–20 mm below the apex. This formation took place in the cortex and was evident in plants grown in darkness or under short pulses of light. Plants grown in continuous red, blue or long wavelength Far red light showed only traces of anthocyanin.     

Apical Growth of Protonemata in Adiantum capillus-veneris IV. Phytochrome-Mediated Induction in Non-Growing Cells

In non-growing two-celled protonemata of Adiantum capillus-veneris,apical growth was induced most effectively by red light irradiation;half of the samples were induced to grow by 660 nm light ofca. 1.5 J m^–2 and the maximum number by ca. 70 J m^–2.The reciprocity law was valid in this photoinduction. The growthresumption became detectable 6 hr after the light irradiationand reached a plateau within 24 hr irrespective of given fluences.When non-growing samples were irradiated with red light of 4.6W m^–2 for 4 sec or shorter, the effect was fully reversedby a subsequent irradiation with far-red light to the far-redlight control level. But, when the red light was given for 16sec or longer, photoreversibility became partial. An interveningdark period of 2 min between red and far-red light did not significantlyinfluence the photoreversibility so that the escape reactionin the dark may not be attributed to the above-mentioned lossof photoreversibility. By means of a local irradiation with a narrow red light beam(10 µm in width), the apical cell was found to be photosensitivefor the growth induction, but basal cell was not. Photoreceptivesite was not localized in any particular region of the apicalcell, but was rather dispersed in the entire apical cell. (Received January 26, 1981; Accepted March 10, 1981)     

Blue Light-Induced In Vivo Absorbance Changes and In Vitro Activation of Nitrate Reductase in a Nitrate-Starved Chlorella Mutant

Illuminating a colorless mutant of Chlorella vulgaris 11h (M125)with blue light caused a reversible photoreduction of b-typecytochrome, i.e., absorbance increases at 423, 525 and 557 nm.This light-induced reduction of cytochrome b was most pronouncedin nitrate-starved cells, which showed some blue light responsesin carbon metabolism, including enhancement of respiration byblue light as reported previously. Prolonged illumination withblue light caused a decrease in the rate of the reduction. The photoactivation of nitrate reductase in the mutant cellswas studied in both cell-free crude extract and purified enzyme.The absorption spectrum of purified enzyme showed three peaksat 423, 525 and 557 nm after the addition of a reductant, indicatingthat the spectrum is that of cytochrome b associated with nitratereductase. Nitrate reductase activity was easily enhanced byblue light illumination after 1 min; red light had no effecton it. The blue light activation of nitrate reductase was notsignificant in growing cells, which showed its high activity. The relationship between the blue light-induced reduction ofcytochrome b and carbon metabolism is discussed. (Received September 30, 1987; Accepted February 9, 1988)     

Reorientation of microtubules at the outer epidermal wall of maize coleoptiles by phytochrome,blue-light photoreceptor,and auxin

Summary The effects of red and blue light on the orientation of cortical microtubules (MTs) underneath the outer epidermal wall of maize (Zea mays L.) coleoptiles were investigated with immunofluorescent techniques. The epidermal cells of dark-grown coleoptiles demonstrated an irregular pattern of regions of parallel MTs with a random distribution of orientations. This pattern could be changed into a uniformly transverse MT alignment with respect to the long cell axis by 1 h of irradiation with red light. This response was transient as the MTs spontaneously shifted into a longitudinal orientation after 1–2 h of continued irradiation. Induction/reversion experiments with short red and far-red light pulses demonstrated the involvement of phytochrome in this response. In contrast to red light, irradiation with blue light induced a stable longitudinal MT alignment which was established within 10 min. The blue-light response could not be affected by subsequent irradiations with red or far-red light indicating the involvement of a separate blue-light photoreceptor which antagonizes the effect of phytochrome. In mixed light treatments with red and blue light, the blue-light photoreceptor always dominated over phytochrome which exhibited an apparently less stable influence on MT orientation. Long-term irradiations with red or blue light up to 6 h did not reveal any rhythmic changes of MT orientation that could be related to the rhythmicity of helicoidal cell-wall structure. Subapical segments isolated from dark-grown coleoptiles maintained a longitudinal MT arrangement even in red light indicating that the responsiveness to phytochrome was lost upon isolation. Conversely auxin induced a transverse MT arrangement in isolated segments even in blue light, indicating that the responsiveness to blue-light photoreceptor was eliminated by the hormone. These complex interactions are discussed in the context of current hypotheses on the functional significance of MT reorientations for cell development.Abbreviations MT cortical microtubule - P_r, P_fr red and far-red absorbing form of phytochrome     

Photostimulation of Hydroxypyruvate Reductase Activity in Peroxisomes of Pharbitis nil Seedlings: II. Photoreceptors in Blue Light

The action spectrum for stimulation of hydroxypyruvate reductase(HPR) activity in etiolated cotyledons of Pharbitis nil showsthe three effective regions of blue (B), red (R), and far red(FR), with high B efficiency. Light duration response curvesand kinetics of stimulation in continuous light were comparedat 455 nm, 660 nm and 710 nm. Before 10 h, the efficienciesat 455 and 660 nm were higher than that at 710 nm. After 10h, lengthening of the 660 nm irradiation was ineffective whilelengthening of the 710 and 455 nm irradiation caused linearincreases in HPR activity. These results together with the effectof pre-R-irradiation on FR or B stimulation suggest that twopigments are simultaneously involved in the B light effect:phytochrome and a specific blue-absorbing pigment. Phytochromemay be the main effective pigment up to 10 h in blue light whilethe blue-absorbing pigment may be more effective for longerexposures. (Received November 22, 1983; Accepted June 20, 1984)     

Ethylene is not involved in the blue light-induced growth inhibition of red light-grown peas

Although the growth of intact plants is inhibited by irradiation with blue light, the growth rate of isolated stem segments is largely unaffected by blue light. We hypothesized that this loss of responsiveness was a result of ethylene production as part of the wounding response. However, we found no interaction between ethylene- and blue light-induced growth inhibition in dark- or red light-grown seedlings of pea (Pisum sativum L.). Inhibition of growth begins in dark-grown seedlings exposed to blue light within 3 min of the onset of blue light, as was known for red light-grown seedlings. By contrast, ethylene-induced inhibition of growth occurs only after a lag of 20 to 30 min or more (dark-grown seedlings) or 60 min (red light-grown seedlings). Also, the inhibition response of red light-grown seedlings is the same whether ethylene is present from the onset of continuous blue-light treatment or not. Finally the spatial distribution of inhibition following blue light was different from that following ethylene treatment.     

The 'end-of-day' phytochrome control of internode elongation in mustard: kinetics, interaction with the previous fluence rate, and ecological implications

Abstract The ‘end-of-day’ phytochrome control of internode growth was characterized in Sinapis alba, seedlings previously grown under continuous white light for 13 d. The transition from white light to darkness caused a reduction in internode extension rate with a lag of less than 10 min. Following this, extension rate remained almost constant for at least 48 h. i.e. ‘re-etiolation’ was not noticed. The phytochorme controlling the growth processes was stable in the Pfr form. The growth rate of plants receiving a red light pulse, and the growth promotion caused by a far-red light pulse, increased with increasing fluence rate of the previous white light treatment. In far-red treated plants a first growth rate acceleration peaked at 20–30 min after the end of white light, followed by a transient deceleration which led to a growth rate minimum at 40–60 min, followed by a final growth rate recovery yielding a more-or-less steady elevated rate. Pulses establishing different Pfr/P modified the extent, but not the early kinetics, of the growth response. The relative promotion of growth caused by low Pfr/P was limited by darkness as follows: (a), The growth promotion caused by far-red directed to the internode alone was transient. (b), The promotion caused by a reduction of Pfr/P in the whole shoot persisted in darkness for at least 48 h and also persisted if, after a 3–9 h dark period, the plants were returned to continuous white light. In darkness, however, the magnitude of this growth rate promotion decreased with time, particularly when the previous white light fluence rate was low, or the pulse preceding darkness provided the lowest Pfr/P. (c), When compared over the same period in darkness, growth rate was higher in those seedlings in which Pfr/P was reduced during the continuous white light pretreatment than in those ones in which the Pfr/P was only reduced immediately before darkness. It is proposed that in the natural environment, red/far-red signals could be more effective when provided during daytime than at the end of the photoperiod, as both the background growth rate and the relative promotion caused by low Pfr/P are reduced by darkness.     

The Comparative Effects of Blue and Red Light on the Stomata of Allium cepa L. and Xanthium pennsylvanicum

Stomatal responses to blue and red light were compared in leavesof Xanthium pennsylvanicum (which contain starch in their guardcells) and in onion leaves (which are devoid of starch). Bluelight was found to be more effective than red in opening stomatain both species. However, a significant difference in the ratiosof blue to red light required to produce equal stomatal openingwas found between Xanthium pennsylvanicum and onion. It is concludedthat blue light may promote stomatal opening by its effect onenzymes controlling the starch and soluble polysaccharide contentof guard cells.     

The Influence of Light on Geotropism in Cress Roots

Light affects the growth and orientation of roots of cress seedlings(Lepidium sativum L. cv. Curled). The effects are manifest eitheras increased rates of geotropic curvature or, if the roots arehorizontal, as distorted and crinkled forms of growth. Blue,red, and far-red irradiation can bring about these effects,but with differences of detail: at equal fluence rates duringthe period of geostimulus, blue is more effective than red atincreasing the rate of geocurvature; however, with irradiationprior to a geostimulus, only the stimulatory effects of redirradiation persist for 2–4 h of darkness. Short periods(5 min) of radiation, if given at the time of geostimulus, enhancegeocurvature, again with blue most, and far-red least, effective,but there are no clear indications of red/far-red reversibility.The possibility of there being more than one photosystem responsiblefor the effects of white light on the geotropic responsivenessof roots is discussed.     

Blue light promotes ionic current influx at the growing apex ofVaucheria terrestris

Irradiation of the growing apex of the algaVaucheria terrestris Götz var.terrestris with blue light (BL), which causes a transient acceleration of growth, also causes a large transient increase in inwardly directed current, which was monitored with a vibrating probe. The growing apex is normally the site of an inward current, and the surface of the non-growing, basal part of the coenocytic cell the site of an outward current. Irradiation of the apex causes only a slight increase in current efflux at the basal part of the cell. The BL-promoted current influx at the apex (BLCI) usually starts within 10 s after the onset of irradiation, preceding the light-growth response. With BL pulses shorter than 3 min, the BLCI reaches a maximum in about 3 min, and then declines to its original value over the next 3 min. If the BL pulse is longer than 3 min, the BLCI continues until the light is turned off. The threshold energy of the BLCI with broad-band BL is 2–5 J·m^-2, i.e. smaller than for both the light-growth response and phototropic response. The maximum BLCI reaches a value of approx. 5 A·cm^-2, equivalent to an influx of 50 pmol·cm^-2·s^-1 of monovalent cations. The effect of red light (RL) is completely different from that of BL: it either causes increases in the inward current of less than 0.3 A·cm^-2, or a transient decrease of current. Furthermore, the direction of the RL-induced change is always the same at the apex and trunk, indicating the participation of photosynthesis. Our results indicate that the BLCI is kinetically and spatially related to the light-growth response and the phototropic bending ofVaucheria. It seems to be a necessary step for the phototropic bending.Abbreviations APW artificial pond water - BL blue light - BLCI blue-light-induced current influx - LGR light-growth response - RL red light