Effects of Anaerobiosis and Respiratory Inhibitors on Blue-Light Inhibition of Spore Germination in Pteris vittata

In a fern, Pteris vittata, inhibition by low-energy blue lightof phytochrome-dependent spore germination was counteractedby anerobiosis and respiratory inhibitors, such as KCN and NaN₃.A 50% inhibition of spore germination in a medium containing0.3 mM NaN₃ required about 8 times longer duration of blue lightirradiation compared with the control. The counteracting effectof NaN₃ continued for about 32 hr after withdrawal of the inhibitor.However, NaN₃ neither induced dark germination nor counteractedthe far-red light inhibition of spore germination. Reducingagents and uncouplers were tested and dithionite and arsenateslightly reversed the blue light inhibition of spore germination. (Received December 17, 1981; Accepted July 8, 1982)     

Action Spectrum between 250 and 800 Nanometers for the Photoinduced Inhibition of Spore Germination in Pteris vittata

An action spectrum between 250 and 800 nm for the inhibitionof red-light-induced germination of spores in the fern Pterisvittata was determined on the Okazaki Large Spectrograph. Theresultant spectrum showed prominent peaks of effectiveness atabout 370, 440 and 730 nm and a minor peak in the neighborhoodof 260 nm. Next, a brief red light irradiation was given immediatelyafter the monochromatic irradiation to cancel the inhibitoryeffect caused by simultaneously formed P_R. This resulted ina complete disappearance of the peak at 730 nm and considerabledecrease of other peaks in the shorter wavelength region exceptat 260 nm. Further correction of the latter spectrum by consideringthe transmission spectrum of a spore coat revealed that 260nm light acted more effectively than lights of 370 and 440 nm.The inhibitory effect of UV light on spore germination was nullifiedby subsequent irradiation with red light for 24 h or darknessfor 48 h followed by a brief red irradiation, indicating thatthe inhibitory action of UV light was ascribable to a blue-ultraviolet light-absorbing pigment. ⁴Present address (KT) and permanent address (MF): Botany Department,Faculty of Science, University of Tokyo, Hongo, Tokyo 113, Japan. (Received July 30, 1983; Accepted November 21, 1983)     

Action of Near UV and Blue Light on the Photocontrol of Phycobiliprotein Formation; A Complementary Chromatic Adaptation

Action of near UV to blue light on photocontrol of phycoerythrin(PE) and phycocyanin (PC) formation was investigated with non-photobleachedTolypothrix tenuis and Fremyella diplosiphon; this study wasdone to evaluate the proposition of Haury and Bogorad [(1977)Plant Physiol., 60: 835] that near UV to blue light is as effectiveas green and red light for photocontrol of PE and PC formationin blue-green algae and that lack of the blue effect in previousexperiments was due to destruction of blue-absorbing pigment(s)by the photobleaching treatment involved in the experimentalmethod. In our present work, light effect was measured in heterotrophiccultures incubated in darkness following brief exposure to differentwavelengths of light. Results indicated that (1) near UV to blue light was not effectivefor induction of PE formation either in T. tenuis or in F. diplosiphon,and (2) PC formation was induced by near UV light at 360 nmbut not by blue light at 460 nm. These features are identicalwith those previously reported for photobleached cells but notwith those reported by Haury and Bogorad for non-photobleachedcells. We conclude that photobleaching treatment does not haveany influence on the action of near UV to blue light. Actionat 390 and 460 nm observed by Haury and Bogorad probably resultedfrom light effects other than photocontrol, e.g., the actionof photosynthesis. (Received December 18, 1981; Accepted April 8, 1982)     

Perithecial Formation in Gelasinospora reticulispora VII: Action Spectra in UV Region for the Photoinduction and the Photoinhibition of Photoinductive Effect Brought by Blue Light

An action spectrum for photoinduction of perithecial formationafter a prior 72 h dark growth period was determined in theUV region with apically growing mycelia of a sordariaceous fungus,Gelasinospora reticulispora. The spectrum exhibited a peak at280 nm. Quantum effectiveness of 280 nm irradiation was ca.1.7 times higher than that of 450 nm light. The number of peritheciainduced by UV radiation was saturated at a lower level as comparedwith blue light. UV radiation having a fluence greater thanthe saturation level decreased the number of induced perithecia.UV radiation that was given after a saturating exposure to inductiveblue light inhibited the inductive effect of blue light. Anaction spectrum for this inhibition exhibited a peak between260 and 270 nm. Monochromatic light beyond 350 nm had no inhibitoryeffect. Inhibitory effects of UV radiation given after inductiveblue light irradiation were observed in the fluence range wherephotoinductive effects of UV radiation became obvious. Therefore,the true height of the UV peak in the photoinduction actionspectrum,when free of distortion from the inhibitory effect, should behigher than the peak obtained in this study. (Received August 20, 1983; Accepted November 4, 1983)     

Action Spectrum in the Ultraviolet Region for Phototropism of Bryopsis Rhizoids

The phototropic response of the rhizoid of the marine coenocyticgreen alga Bryopsis plumosa to ultraviolet light (250–350nm) was investigated. The rhizoid exhibited negative bendingthat was due to bulging upon absorption of light in the UV region,as well as in the visible region, of the spectrum. The negativebending might not be a result of the inhibition of growth onthe irradiated side of the apical hemisphere by UV irradiationbecause growth inhibition was observed after bending had reacheda maximum within one to two hours. The action spectrum obtainedfrom fluence rate-response curves had a pronounced peak at 260nm and a small peak at 310 nm. The quantum effectiveness at260 nm was about five times that in the visible region. Phenylaceticacid (PAA), a potent inhibitor of flavin photoreactions, inhibitedthe phototropic response to both UV light and blue light withoutany obvious effect on tip growth. The inhibition of the phototropicresponse to blue light by PAA was partially overcome by rinsingthe alga with riboflavin-containing medium, which result suggeststhe involvement of flavins in the phototropism of Bryopsis rhizoids. (Received February 6, 1995; Accepted June 19, 1995)     

Action Spectra for Stimulatory and Inhibitory Effects of UV and Blue Light on Fruit-Body Formation in Coprinus congregatus

Spectral sensitivity for stimulatory and inhibitory effectsof light on fruit-body formation in Coprinus congregatus wasdetermined between 250 and 730 nm using the Okazaki Large Spectrograph.Eight-day-old dark grown cultures were exposed to varying amountsof monochromatic photon fluences for 60 s. Primordial initiationwas strictly localized in the youngest hyphae of the culture.After a dark period of 24 h at 25C, the primordial initiationwas assayed by counting the number of primordia. The actionspectrum showed peaks of effectiveness at 260, 280, 370 and440 nm. The quantum effectiveness at 280 nm was 4 times higherthan that at 440 nm. The lethal effect of far UV (260–280nm) was demonstrated when using 100 times higher photon fluencesthan that inducing primordial formation. The primordia growing in continuous light required an uninterrupteddark period for 5 h at 25C to produce sporulating fruit-bodies.A brief exposure to light during the dark period inhibited thedevelopment of primordia. The action spectrum for this photoinhibitoryeffect showed maxima at 280, 350, 380, 440 and 460 nm. The quantumeffectiveness at 280 nm was Ca. 1.3 times higher than that ofblue light. The spectral sensitivities for primordial initiationand for inhibition of primordial development were quite similarand suggested a common photoreceptor during fruit-body morphogenesis. ⁴ Permanent address: Botany Department, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan.     

Effects of Calcium and Potassium Ions on Phototaxis in Cryptomonas

Effects on positive phototaxis and the cell motility of 7 cationsin 5mM MOPS (morpholinopropane sulfonic acid) buffer (pH 7.0)containing 0.16 mM NaCl, 0.68 mM KCl, 0.5 mM CaCl₂ and 0.16mM MgCl₂ were studied in the unicellular flagellate Cryptomonaswith a photoelectrical measuring apparatus and photomicrography.When calcium ion was removed from the medium by adding 1 mMEGTA (ethylene glycol-bis-(ß-amino-ethylether)-N,N'-tetraaceticacid), the phototactic response was totally inhibited, but theswimming rate was not much affected. The effect of EGTA waspartially reversed by the addition of 1 mM CaCl₂. When 15mMKCl or RbCl was added to the medium, phototaxis was greatlyinhibited, but there was no significant influence on the swimmingrate. Similar but less inhibitory effects were induced in thepresence of NaCl, LiCl and CsCl. KCl-induced inhibition waspartially removed by the addition of 15 mM CaCl₂ or MgCl₂. (Received June 25, 1982; Accepted September 27, 1982)     

Analysis of substances issuing from Zajdela ascitic hepatoma cells after exposure to UV radiation of different wave-lengths. I. Relationship to dose]

The release of substances from the Zaidela ascitic hepatoma cells after irradiation with physiological doses of short-wave (254 nm) and long-wave (300-380 nm) UV light (far and near UV light) has been studied spectrophotometrically. Within the range of 200-520 nm, the absorption spectra of releasing substances show maxima at 215 and 260 nm and are identical to spectra of non-irradiated cells. The amount of substances increases with dose making up, at the maximal alteration, 180-220%, of the amount releasing from non-irradiated cells. Irradiation with far UV light exceeds by one order that with near UV light. The effect of minimum doses is opposite to the action of high doses: the release of substances from irradiated cells is much less.     

Effect of preincubation UV irradiation of abscisic acid and gibberellin A3 on {alpha}-amylase induction in barley half-seeds

A 24 hr preincubation UV (254 nm) irradiation of RS-ABA andGA₃ solutions completely negated the inhibitory effect of ABAon GA₃ induced -amylase production with barley half-seeds. Thisirradiation, however, caused no significant inhibition of GA₃-induced-amylase production. UV treatment of an extract from Tulipaindicated that this technique can be used to photooxidize ABA-likesubstances present in plant extracts. ¹ Michigan Agricultural Experiment Station Journal Article No.5774. This research was supported in part by a grant from theNetherlands Flower-Bulb Institute, New York and the OrnamentalMarketing Board, The Hague. ² Present address: Istituto di Orticoltura e Floricoltura, Universitàdegli Studi di Pisa, 56100, Italy. (Received February 26, 1972; )     

Effects of blue light on respiration and carbon dioxide fixation in colorless Chlorella mutant cells

A colorless mutant of Chlorella vulgaris (Mutant #125) starvedin darkness, showed suppressed rates of respiration and darkCO₂ fixation, which were significantly recovered by illuminationwith blue light. The main CO₂ fixation product under blue lightwas aspartate. Such enhancements did not take place in cellsactively growing in the glucose medium. Both enhancing effectsof blue light (456 nm) were saturated at light intensities aslow as 400–800 erg.cm^-2.sec^-1. The action spectra forthese enhancing effects were similar to each other; both showedpeaks at 460 nm and 380 nm, which correspond to the absorptionmaxima of flavin. All these findings indicate that the samemechanism underlies the observed effects of blue light on CO₂fixation and respiration. The role of blue light which bringsabout the enhancements in CO₂ fixation and respiration is discussed. (Received June 1, 1974; )     

Photosynthetic Properties of Guard Cell Protoplasts from Vicia faba L.

Guard cell protoplasts were isolated enzymatically from theepidermis of Vicia faba L. and their photosynthetic activitieswere investigated. Time courses of light-induced changes inthe chlorophyll a fluorescence intensity of these protoplastsshowed essentially the same induction kinetics as found formesophyll protoplasts of Vicia. The transient change in thefluorescence intensity was affected by DCMU, an inhibitor ofphotosystem II; by phenylmercuric acetate, an inhibitor of ferredoxinand ferredoxin NADP reductase; and by methyl viologen, an acceptorof photosystem I. Low temperature (77 K) emission spectra ofthe protoplasts had peaks at 684 and 735 nm and a shoulder near695 nm. A high O₂ uptake (175 µmol mg^–1 Chl hr^–1)was observed in guard cell protoplasts kept in darkness, whichwas inhibited by 2 mM KCN or NaN₃ by about 60%. On illumination,this O₂ uptake was partially or completely suppressed, but itssuppression was removed by DCMU, which indicates that oxygenwas evolved (150 µmol mg^–1 Chl hr^–1) photosynthetically.We concluded that both photosystems I and II function in guardcell chloroplasts and that these protoplasts have high respiratoryactivity. (Received January 30, 1982; Accepted May 15, 1982)     

Photomorphogenic responses to UV radiation: Involvement of phytochrome and UV photoreceptors in the control of hypocotyl elongation in Lycopersicon esculentum

The photo-inhibition of Lycopersicon esculentum Mill, hypocotyl growth induced by UV radiation may be mediated by both phytochrome and UV-absorbing receptors. The inhibition of growth induced by continuous irradiation with high fluence rate UV radiation is similar in the au mutant, which is severely deficient in spectrophoto metrically and immunochemically detectable phytochrome, and in the isogenic wild type. Parallel irradiation with 692 nm light, which is equivalent to UV radiation for the phytochrome system in our experimental conditions, induced at high photon fluence rates a significant increase in hypocotyl growth in the au mutant. The same light treatments inhibited the hypocotyl growth of the wild type. The responses of water-grown seedlings and chlorophyll-free seedlings (streptomycin and norflurazon treated seedlings) were compared. Water-grown and chlorophyll-free seedlings responded similarly to UV radiation. The presence of chlorophyll correlates with a significant increase in hypocotyl growth of au mutants irradiated with 692 nm light. These results support the conclusion that UV-induced inhibition of growth in the au mutant is independent of phytochrome.     

Purification and Characterisation of the Light and Dark Forms of Phosphoenolpyruvate Carboxylase from the Dicot Plant Amaranthus viridis L. An Examination of Its Kinetic and Regulatory Properties in the Presence of Water-Alcohol Binary Solvents

The light and dark forms of phosphoenolpyruvate (PEP) carboxylase(PEPC) from the dicot plant Amaranthus viridis L. were purifiedand their kinetic properties were studied in water-based orbinary alcohol-water solvents. At pH 7.3, the specific activityof the purified light form was about 2.7-fold higher than thatpresented by the dark form of PEPC under optimal conditions,while K_m remained virtually unchanged in both forms. The enzyme'slight form was better activated by glucose 6-phosphate and lessinhibited by L-malate than the dark PEPC. From the organic solventsstudied, methanol showed the most important effect, enhancingPEPC activity by two-fold at 20% (v/v). Ethanol, ethylene glycol,tert-butanol and 2-propanol were also activators to a lesserdegree, but at high concentrations (typically greater than 20%,v/v) the effect was reduced or turned to inhibition. K_m (PEP)was reduced by an order of magnitude in the presence of 20%(v/v) methanol (i.e. from 0.32 to 0.022 mM for the light formof the enzyme). The inhibitory effect of malate at low PEP waslessened by methanol for both forms (i.e. I₅₀ 0.25 mM in aqueousmedium to 0.48 mM in binary mixture for the dark form), whileglucose-6-P activation of PEPC was not affected by methanol.The results suggest that the kinetics of PEPC in a medium thatmimics more closely in vivo conditions are different from thoseobserved by standard procedures consisting of aqueous media,and provide a new insight on the properties of PEPC as relatedto its regulation in vivo. (Received June 26, 1995; Accepted August 24, 1995)     

Destructive changes in the outer perimembrane layers (glycocalyx) of Zajdela ascites hepatoma cells under the action of UV radiation]

Immediately after far (254) nm and near (300--380 nm) UV light in small and moderate doses alcian blue sorption by glycocalix of Zaidela ascitic hepatoma cells decrease, which is indicative of destruction and solubilization. The effect of UV light on the cell surface is compared with the action of trypsin. Contribution of the damage of outer perimembrane layers to the lethal effect of UV light is discussed.     

Effects of disalicylidenepropandiamine and near far-red light on 14CO2-fixation in Chlorella cells

1) With Chlorella ellipsoidea cells, in the presence of 5x10^–6M DSPD, or in its absence, the amounts of ¹⁴CO₂ incorporatedin P-esters, serine-plus-glycine and alanine were larger underred light than under blue light, whereas blue light specificallyincreased ¹⁴CO₂-incorporation in aspartate, glutamate, malateand fumarate (blue light effect). The amount of total ¹⁴C fixedunder blue or red light was greatly decreased by the additionof DSPD. When the concentration of DSPD was raised to 5x10^–4M, practically no radioactivity was found, under blue or redlight, in aspartate, glutamate and fumarate. Radioactivity inalanine was greatly increased. Effects of higher concentrationof DSPD are explained as due to the inhibition of PEP carboxylaseactivity in Chlorella cells. 2) The percentage incorporation of ¹⁴C into aspartate and theother compounds mentioned above, under near infra-red illuminationwas significantly smaller than that under blue light and wasalmost equal to that under red light. These results along withthe effect of 5x10^–6 M DSPD, exclude the possibility thatcyclic photophosphorylation is involved in the "blue light effect"mechanism. (Received December 12, 1969; )     

Analysis of substances released from Zajdela ascites hepatoma cells exposed to UV radiation of different wavelengths. III. Release of nucleoproteins and carbohydrates]

Irradiation of the Zaidela ascite hepatoma cells with physiological doses of shortwave length (254 nm) and longwave length (300-380 nm) UV light (far and near UV radiation) is accompanied by the release of ribonucleoproteins (RNP) from the cells, whose amounts increase with dose. Irradiation with far and near UV light leads to the release of high-molecular and low-molecular RNP, respectively. No deoxyribonucleoprotein were found among the released substances. Non-protein fractions, released from irradiated cells, contain carbohydrate-like substances. At maximum far and near UV doses the amounts of these substances constitute 180-190% of the control and 6% of their amount in intact cells. After irradiation with far UV light, relatively high-molecular carbohydrates are released, while near UV light treatment induces the release of low-molecular carbohydrates. The criteria tested show that the efficiency of far UV light exceeds that of near UV light by one order.     

Wavelength options for monitoring leghaemoglobin oxygenation gradients in intact legume root nodules

Nodule oximetry, based on spectrophotometric measurements ofleghaemoglobin (Lb) oxygenation in intact nodules, has providednumerous insights into legume nodule physiology. Fractionaloxygenation of Lb (FOL) has been monitored at various wavelengths,but comparisons among wavelengths have not been published previously.Changes in transmittance were monitored simultaneously at 660nm and either 560 or 580 nm as FOL was manipulated by changingthe O₂ concentration around nodules of Medicago sativa L. orLotus comiculatus L. Video microscopy at 580 nm was used togenerate two-dimensional maps of FOL gradients in intact nodules.In general, all three wavelengths gave similar results. Smalldiscrepancies between 660 and 580 nm, sometimes seen in noduleswith high O₂ permeability, may indicate interference by theferric Lb peak at 625 nm. A slightly longer wavelength, forexample 670 nm, might be preferable. No significant discrepanciesamong wavelengths were seen in nodules whose O₂ permeabilityhad been reduced by a 48 h exposure to 10 mM nitrate. Minorgradients in FOL were seen in nodules of M. sativa and Trifoliumrepens L. under air and steeper gradients could be induced byvarious treatments. The existence of these gradients indicatesat least some restriction of longrange O₂ diffusion within theinfected zone. The FOL maps do not have enough spatial resolutionto measure gradients within infected cells. Key words: Leghaernoglobin oxygenation, nodules, spectrophotometry, nodule oximetry     

Spectral dependences of flowering in Lemna perpusilla and L. gibba

Floral induction in Lemna perpusilla and L. gibba was determinedunder continuous irradiation with monochromatic light in spectralranges from 396 to 765 nm. In the former it was induced underwavelengths from about 400 to 550 nm and longer than 700 nm,while in the latter with wavelengths near 400 nm and from about550 to 650 nm. The patterns of these spectral dependences werenearly mirror images and corresponded to the P_fr level in thephotostationary states of phytochrome. (Received December 3, 1974; )     

Flowering of the long-day plant, Lemna gibba, under short-day schedules composed of red and far-red light

Flowering in Lemna gibba, a long-day duckweed, can be inducedunder a short-day condition when the photoperiodic regimes areR₇FR₃ (7 hr red followed by 3 hr far-red), R₅FR₅ and R₃FR₇.This indicates the necessity of a proper balance between redand far-red effects for flowering. The flowering induced bythese regimes is inhibited by a brief exposure to red givenat the start of darkness and this inhibition is reversed bysubsequent exposure to far-red. Thus, the red/far-red reversibleeffect is found only at the beginning of darkness for floweringof L. gibba. However, flowering of L. gibba is promoted by a red light breakgiven near the middle of a 14 hr dark period. The promotiveeffect is not reversed by subsequent exposure to far-red, i.e.,the effect of the red break converts from inhibition to promotionas when given later in the dark period, which suggests the involvementof a timing mechanism. (Received July 21, 1973; )     

The Inhibition of Growth by Gravitropic Stimulation in Darkness in Agravitropic Primary Roots of Zea and the Role of Calcium

The primary roots of the "Golden Cross Bantam 70" cultivar ofZea mays are agravitropic in darkness and their orthogravitropismis light-dependent. Analysis of the agravitropic roots providesimportant information about the mechanism of orthogravitropism.However, the underlying mechanism of the agravitropic responsein darkness is unknown. We found that the growth of intact primaryroots was inhibited by gravitropic stimulation (i.e., changingthe orientation of the roots from vertical to horizontal) indarkness, but that of detipped roots was not. The role of calciumin this gravistimulation-dependent inhibition of growth wasinvestigated using apical 5-mm segments of the primary roots.The gravistimulation-dependent inhibition of growth was preventedby applying 10 mM MES-KOH buffer at pH 6.0 to the root cap.By contrast, the application of 0.1–1 mM buffer at pH6.0 and 10 mM buffer at pH 4.5–5.0 allowed the gravistimulation-dependentinhibition of growth. Furthermore, when the buffer of 10 mM(pH 6.0) contained 1–5 mM CaCl₂, the gravistimulation-dependentinhibition of growth was apparent. By contrast, when weak (1mM) buffer at pH 6.0 or 10 mM buffer at pH 4.5 contained 5 mMEGTA, no gravistimulation-dependent inhibition of growth wasobserved. Thus, the gravistimulation-dependent inhibition ofgrowth in darkness seemed to be mediated by an increase in thelevel of free Ca²⁺ in the root tip. These results suggest thatfree Ca²⁺ in the apoplast of the root tip plays an importantrole in the agravitropic response in darkness as well as inorthogravitropism under light of the roots of this cultivarof Zea mays. (Received March 21, 1994; Accepted July 25, 1994)