On the Mechanism of Phase Control by Light in the Rhythm of Carbon Dioxide Output in Leaves of Bryophyllum fedtschenkoi

The induction of phase shifts in the rhythm of CO₂ output inleaves of Bryophyllum fedtschenkoi kept in continuous darknessand a CO₂-free air stream at 15 °C has been investigatedby scanning the circadian cycle with 1-h and 3-h exposures tolow fluence rates of red light. The experiments were designedto test the hypothesis (Wilkins, 1983) that phase-shift inductionwas achieved by the redistribution of malate between the vacuolarand cytoplasmic compartments of the leaf cells due to red lightopening ‘gates’ in the tonoplast through which malatediffusion can take place. The use of red light exposures oftwo different durations enabled the direction of phase shiftsto be established. From 8 h to about 22 h of darkness, whenthe cytoplasm would be expected to have a higher level of malatethan the vacuole, only phase advances were observed, as predictedfrom the hypothesis. At later times in the cycle, phase delaysand then phase advances were induced in a pattern closely similarto that reported for high temperature treatments (Wilkins, 1983).The results are discussed in relation to the tonoplast gatehypothesis which appears to account adequately for every featureof the phase shifts induced by exposing leaves to red light. Key words: Bryophyllum fedtschenkoi, Circadian rhythm, CO² fixation, phase control, red light, malate transport     

An Endogenous Rhythm in the Rate of CO2 Output of Bryophyllum: II. THE EFFECTS OF LIGHT AND DARKNESS ON THE PHASE AND PERIOD OF THE RHYTHM

The effects of light, darkness, and changes in light intensityon the phase and period of the endogenous rhythm in the rateof CO₂ output of excised leaves of Bryophyllum fedtschenkoihave been examined. The duration, intensity, and wavelength of a short light treatment,and the point in the cycle at which it is administered, determinethe degree of phase shift induced in a rhythm persisting indarkness. When light treatments of 3 and 6 hours' duration,at an intensity of 3,000 lux, are applied between the peaksthe phase is completely reset, the first post-treatment peakoccurring 18–19 hours after the end of the treatment.The degree of phase shift is therefore determined not by theduration of the treatment but by the time at which the treatmentterminates. One hour's illumination has little or no effect.The phase is unaffected when light treatments of up to 5 hours'duration at an intensity of 3,000 lux are applied at the crestof a peak. Over the range 8-3,000 lux the intensity of lightduring a 6-hour treatment applied between the peaks does notaffect the efficiency with which that treatment completely resetsthe phase. At an intensity of 2 lux, however, the phase delayis equal to the duration of the treatment. A 6-hour red-light treatment (850 ergs/cm.²/sec.) applied betweenthe peaks completely resets the phase whereas blue light (10,860ergs/cm.²/sec.) has no effect on the phase but induces a slightprotraction of the period. Moreover, continuous red light inhibitsthe rhythm, which recommences in blue light. A rhythm is induced in illuminated leaves when the light intensityis either gradually or suddenly reduced by at least 80 per cent.Whether a given intensity of illumination inhibits or permitsthe persistence of a rhythm depends upon the light intensityby which it is immediately preceded. A rhythm will persist in illuminated leaves for approximatelyas long as in leaves in darkness and the phase shows no correlationwith time of day. The period is unaffected by the intensityof white light (from 0-500 lux) to which the leaves are subjected.The duration of a short dark treatment, and the point in thecycle at which it is applied, determine the degree of phaseshift induced in a rhythm in illuminated leaves. The phase isreset when 3-, 6-, and 9-hour dark treatments are applied atthe crest of a peak, the amount of phase shift increasing toa maximum with 9 hours' darkness. The phase shift is not equalto the duration of the treatment. The phase is unaffected when3- and 6-hour dark treatments are applied between the peaks. The variation in the sensitivity of the phase of a rhythm persistingin darkness to short light treatments is in the opposite senseto that of a rhythm persisting in light to short dark treatments.The phase of a rhythm in illuminated leaves is completely resetwhen the leaves are transferred to continuous darkness commencingeither at the crest of, or between, the peaks. The results are discussed and compared with those of other authors.     

Effects of Light Quality on Formation of 5-Aminolevulinic Acid, Phycoerythrin and Chlorophyll in Cryptomonas sp. Cells Collected from the Subsurface Chlorophyll Layer

Phycoerythrin obtained from the cells of Cryptomonas sp. (Cryptophyceae)which had been isolated from the subsurface chlorophyll layerin the western Pacific Ocean showed peaks in absorption andfluorescence spectra at 545 and 586 nm, respectively. The rateof photosynthetic O₂ evolution under green light was higherthan those under blue and red light. The rate of 5-aminolevulinic acid (ALA) accumulation in thepresence of levulinic acid was higher under green light thanunder blue and red light. The effects of light quality on therates of O₂ evolution and ALA formation closely resembled eachother. On the other hand, the formation of phycoerythrin andALA was suppressed during growth under blue light. Possible effects of light quality on the formation of photosyntheticpigments in Cryptomonas sp. were discussed. (Received January 31, 1984; Accepted May 14, 1984)     

Effects of lanthanum on rhythmic and nyctinastic leaflet movements in Albizzia lophantha

The involvement of extracellular calcium in rhythmic and nyctinasticmovement oi Albizzia lophantha Benth. leaflets has been studiedby testing the effect of LaCl₃ and its interaction with thephytochrome control of these movements. A 2h pulse of LaCl₃(10–50 mM) promotes a loss of rhythmicity, leaving leafletsin an open position, and also overrides the phase shift causedby phytochrome. A 2 h pulse of LaCl₃ (1 mM) decreases the amplitudeof rhythmic oscillations but does not promote arhythmicity normodify the phase shift caused by red light. The red light pulseabolishes the damping effect of 1 mM La³⁺. LaCl₃ inhibits nyctinasticclosure and decreases the phytochrome control of nyctinasticclosure. A subsequent supply of CaCl₂ (10 to 100 mM) does notreverse La³⁺ (10 mM) inhibition of closure. Light-induced openingis independent of LaCl, but rhythmic opening in darkness showsdifferent responses to La³⁺ depending on the time at which La³⁺is applied. Data suggest that extracellular calcium is requiredfor the closure mechanism and for the expression of rhythmicmovement. It could also be involved in the phytochrome transductionpathway and/or in the linking steps between phytochrome andthe circadian clock. Key words: Albizzia lophantha, calcium, circadian rhythm, lanthanum, phytochrome     

Der Einflu{beta} verschiedener Lichtqualitaten auf Chlorophyllgehalt und Wachstum von Gewebekulturen aus Crepis capillaris (L.) WALLR.

The influence of different light qualities on chlorophyll contentand growth of tissue cultures from Crepis capillaris (L.) WALLR. Tissue cultures from Crepis capillaris growing on media (M₁; M₂ ; M₂-E) formed chlorophyll and intact chloroplasts onlyin the short wave length region of the visible spectrum (350–550nm). In red light (600–700 nm) as well as in darknessthey lost their chlorophyll after 8–10 weeks. The growth of Crepis-cultures was strongly influenced by lightand the nitrogen of the medium. The highest increase in freshweight (425–485% increase in 3 weeks) was attained inred light or in darkness on M₂ by cultures which had lost theirchlorophyll completely. M₂ contains nitrates, ammonium saltsand amino acids. In contrast, the increase in fresh weight ofgreen cultures growing on M₂ in blue or white light was considerablylower (155–180% increase in 3 weeks). Omission of amino acids, (M₂-E), resulted in the reduction ofthe growth (increase of fresh weight in 3 weeks: 120%) of thechlorophyll-free cells growing in the dark. Green cultures behaveddifferently on M₂-E. In white light they attained an increasein fresh weight of 245%. This suggests that the growth promotingeffect of the amino acids can be replaced by light. Results with cultures growing on M₁, which contains neitherammonium salts nor amino acids, point in the same direction.Green cultures in white or blue light grew better (90–100%increase in fresh weight in 3 weeks) on this "deficient" mediumthan chlorophyll-free tissues in red light or in darkness (20–30%increase in fresh weight in 3 weeks). Some aspects of thesefindings which concern the effect of light on growth are discussed. (Received November 28, 1969; )     

The Damping and Reinitiation of the Circadian Rhythm of CO2 Output in Bryophyllum Leaves in Relation to their Malate Content

The circadian rhythm of CO₂ output in leaves of Bryophyllumfedtschenkoi damps out after 3–4 d in continuous darknessand a CO₂-free air stream at 15°C. The rhythm is reinitiatedafter a single exposure to white light of 2, 4, 6 or 8 h duration,damps out again after a further 3–4 d and can be reinitiatedfor a second time by a further exposure to light. During the exposure to light there is a burst of CO₂ outputconsistent with the decarboxylation of malate, and the rhythmbegins afterwards with an initial high rate of CO₂ fixation.Malate gradually accumulates in the leaves in continuous darknessto attain a maximum value (35 mol m^–3) at the time whenthe circadian rhythm disappears, and decreases to a low value(19 mol m^–3) after a 4 h exposure to light which reinitiatesrhythmicity. These results support the hypothesis that damping of the rhythmof CO₂ output in continuous darkness is due to the accumulationof malate in the leaf cells, eventually reaching such a levelthat its removal from the cytoplasm into the vacuole cannottake place, with the result that PEPc activity, upon which therhythm of CO₂ output depends, remains allosterically inhibited. Key words: CAM, circadian rhythm, Bryophyllum, CO₂-fixation, malate metabolism     

Germination of seeds in Jussiaea suffruticosa

Seeds of Jussiaea suffruticosa reach high germination percentagesonly when exposed to long periods of continuous illumination.The light reaction may be repeatedly reversed by short exposuresto red and far red light, thus being mediated by the phytochromesystem. Seeds also germinate at high percentages if exposedto various cycles of 1 hr light and 24 hr of darkness at 20°C.If the temperature in the periods of darkness is raised up to30°C or lowered to 10°C the promotive effect of lightis inhibited. High temperatures (35°C) during imbibitionhave a promotive effect, whereas a pure O₂ atmosphere decreasesthe response to light. KNO₃ and kinetin enhance the responseto light but do not provoke germination in the dark. Only ifseed coats are punctured or removed does germination in thedark occur. (Received January 14, 1969; )     

Green Light Drives CO2 Fixation Deep within Leaves

Maximal ^l4CO₂-fixation in spinach occurs in the middle of thepalisade mesophyll [Nishio et al. (1993) Plant Cell 5: 953],however, ninety percent of the blue and red light is attenuatedin the upper twenty percent of a spinach leaf [Cui et al. (1991)Plant Cell Environ. 14: 493]. In this report, we showed thatgreen light drives ¹⁴CO₂-fixation deep within spinach leavescompared to red and blue light. Blue light caused fixation mainlyin the palisade mesophyll of the leaf, whereas red light drovefixation slightly deeper into the leaf than did blue light.¹⁴CO₂-fixation measured under green light resulted in less fixationin the upper epidermal layer (guard cells) and upper most palisademesophyll compared to red and blue light, but led to more fixationdeeper in the leaf than that caused by either red or blue light.Saturating white, red, or green light resulted in similar maximal¹⁴CO₂-fixation rates, whereas under the highest irradiance ofblue light given, carbon fixation was not saturated, but itasymptotically approached the maximal ¹⁴CO₂-fixation rates attainedunder the other types of light. The importance of green lightin photosynthesis is discussed. ¹Supported in part by grants from Competitive Research GrantsOffice, U.S. Department of Agriculture (Nos. 91-37100-6672 and93-37100-8855).     

Control of the Entry into S Phase by Phytochrome and Blue Light Receptor in the First Cell Cycle of Fern Spores

Phytochrome- and a blue light receptor-dependent pathway antagonisticallyregulate the first mitosis in spores of the fern Adiantum capillus-venerisL. This study focused on determining which phase(s) of the cellcycle is positively regulated by phytochrome and negativelyregulated by a blue light receptor in germinating spores. Incorporationof the radioactivity of ³H-thymidine into the acid-insolublematerial prepared from the spores indicated that phytochromein the PFR form induced the entry into S phase of the firstcell cycle in the spores 20-28 h after irradiation with redlight. Blue light treatment before or after red light treatmenttotally prevented the P_FR-induced DNA synthesis. Brief irradiationwith red, far-red or blue light showed no effects on mitosisif the irradiation was given 28 h after the red light induction,during S and M phases. These results indicate that phytochromeand a blue light receptor regulate the entry into S phase duringthe first cell cycle of fern spores. ( Accepted July 10, 1997)     

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; )     

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; )     

Some Biochemical Changes Related to Starch Breakdown Induced by Blue Light Illumination and by Addition of Ammonia to Chlorella Cells

Illumination with blue light enhanced the production of ammoniaby cells of C. vulgaris 11h, while no such effect was inducedby red light illumination. Addition of ammonia caused increasesin ATP levels and decreases in Pi and ADP levels. When 5 mMNH₄Cl was added to phosphorylase and amylase isolated from thecells of C. vulgaris 11h, their activities increased about 5–15%and 40–100%, respectively. (Received June 21, 1986; Accepted December 23, 1986)     

Relationship between Photosynthesis and Plasmalemma Transport

Hansen, U.-P., Kolbowski, J. and Dau, H. 1987. Relationshipbetween photosynthesis and plasmalemma transport.—J. exp.Bot. 38: 1965–1981. The yield of chlorophyll-fluorescence (F), of oxygen evolution(PAS, photo-acoustic signal) and the light-induced changes ofplasmalemma potential (V) were measured in the presence of red(633 nm) background light with blue or far-red (720 nm) sinusoidallymodulated actinic light. The kinetic study based on curve-fittingof the measured frequency responses led to the following: theresponse of chlorophyll-fluorescence (F) to blue actinic lightcomprises four time-constants located at 2·7,50,400 and4000 s. Membrane potential (V) displays five time-constants:2· 50, 160±330, —1, 4000 s. These time-constantswere assigned to the reactions involved as follows: from thecomparison of the effects of blue and far-red actinic lightthe time-constants of 2·7 s and 400 s were related tothe plastoquinone pool and to the state-transition controller.The time-constant of 4000 s was not investigated. The complextime-constants of V are known to be related to the controllerof cytoplasmic pH from previous studies. The time-constant of50 s was common to V, F, and PAS. From the sign of the 50 scomponent in F and in PAS (q_E-component), the following modelof the light action on membrane transport was developed: theuptake of protons into the inner space of the thylakoids causesan alkalinization of the cytoplasm which slows down the plasmalemmaH₊-pump via a substrate effect. Key words: Chlorophyll-fluorescence, frequency responses, kinetic analysis, plasmalemma potential, photo-acoustic effect, proton flux, spinach, state-transitions, thylakoid membrane, time-constants     

Effects of Monochromatic Radiations on Growth of Pelargonium Callus Tissue

Pith callus tissues were grown under continuous blue (450 mµ),green (545 mµ), red (650 mµ), and ‘white’(full-spectrum) light, and in the dark for 22 days at 27±2°C at energy levels of 15,000 ergs cm^–2 sec^–1. Mean increases in fresh weight of tissues grown under ‘white’and blue light were significantly greater than those of tissuesgrown in green and red light and in the dark. Tissues grownin the dark yielded mean fresh weight increases significantlylower than tissues grown under blue, red, and ‘white’light. No significant differences were shown between blue and‘white’, red and green, and green and dark treatmentsrespectively. Cell differentiation occurred in all treatmentsonly to the extent of vessel element formation. There were nodifferences in degree of differentiation between treatments. It was proposed that the high-energy reaction of photomorphogenesiswas in operation in the Pelargonium callus tissue. The resultsindicated the presence in the tissue of high-energy photoreceptor(s).The use of high-intensity, incandescent illumination for experimentalprocedures approximating natural conditions of irradiation wasindicated as desirable for pith callus tissues of Pelargoniumzonale var. Enchantress Fiat.     

The Occurrence of Endogenous Rhythms in the Coleoptiles in Various Cereal Genera

The rate of growth of the coleoptiles was determined from photographstaken by infra-red radiation. CO₂ output was measured by meansof an infra-red gas analyser. The rhythm of CO₂ output from the coleoptile of Avena was inducedby a change from red light to darkness. It has a period of about24 hours and agrees in timing with the growth-rate rhythm previouslyrecorded. Some degree of rhythmicity in the growth-rate was found in Triticumvulgare (var. ‘Eclipse’) and in Secale cereale (var.Petkus). Very slight indications of rhythmicity were found inTriticum spelta and in Hordeum vulgare. Negative results wereobtained with Oryza sativa and with Zea mays. Where rhythmicityin the coleoptile is less strongly developed, the peaks comecloser together, the interval being about 18–20 hours.Cereals cannot be sharply separated into two groups accordingto the presence or absence of rhythmicity in the coleoptile.Of the genera examined, the most marked endogenous rhythms occurin Avena. It is doubtful if the ability of the coleoptile toexhibit an endogenous rhythm has any beneficial effect on thedevelopment of the seedling. Under normal conditions of germinationinduction of the rhythm would not occur.     

The involvement of photosynthesis in inducing bud formation on excised leaf segments of Heloniopsis orientalis (Liliaceae)

The role of photosynthesis in inducing adventitious bud formationon leaf segments of Heloniopsis orientalis was investigated.The effect of white light reached a maximum at about l25 J?m^–2?sec^–1.White, red, blue and far-red light were effective in inducingbud formation, but green light was not. In darkness, bud formationwas induced if sugar was added to the nutrient medium. The photosyntheticinhibitors DCMU and AT blocked the effect of light. Bud formationwas inhibited in CO₂-free air. The requirement of sucrose forbud formation in darkness could be replaced by citrate. It wasconcluded from these results that light appears to induce budson leaf segments through some processes dependent upon photosynthesis. (Received January 11, 1978; )     

Rhizoid differentiation in Spirogyra II. Photoreversibility of rhizoid induction by red and far-red light

The optimum light conditions for rhizoid formation in Spirogyrawere determined. Red light was significantly effective on rhizoidformation while green, blue and violet lights had less effect.The dose-effect curve of red light was investigated and theminimum energy needed to saturate the effect was 8.1 Kergs.cm_–2.The effect of red light was completely reversed by subsequentirradiation with far-red light. The doseeffect curve of far-redlight was also obtained. The repeatedly reversible photoresponseswith red and far-red light strongly suggest that the photoreceptorof the rhizoid formation system is phytochrome. The existenceof phytochrome in the Spirogyra cell was also demonstrated spectrophotometrically.The half time for the escape reaction from the reversal effectof far-red light was 2hr. There may be no pigment other thanphytochrome mediating the photoreaction. (Received December 14, 1972; )     

Low Temperature Spectrophotometry on Phototransformation of PR in Pelletable Phytochrome of Pea

Phototransformation of P_R to P_FR in a 1,000–7,000 x gpelletable fraction (1–7 KP), which was extracted fromdark-grown pea shoots that had been irradiated by red then far-redlight, was studied by low temperature spectrophotometry. Redlight irradiation of P_R in 1–7 KP at –160°Cinduced an absorption increase at 695–696 nm with a concomitant,small decrease of P_R absorption at 670 nm. These changes werepartially photoreversed when the sample was irradiated subsequentlywith 700-nm light. At –55°C, red light irradiationof P_R resulted mainly in bleaching and consequently in a reductionof the P_R peak, accompanied by minor absorbance increases around695 nm. The intermediates formed at –165°C by 660-nmlight irradiation partly reverted back to P_R or formed a bleachedintermediate (probably the same bleached intermediate describedabove) in the dark, when the pellets were warmed to –60°C.The bleached intermediate was transformed to P_FR in the darkat –10°C or above. These characteristics of P_R transformation observed in the pelletablephytochrome were essentially the same as those observed in invivo or soluble phytochrome. (Received December 24, 1982; Accepted July 28, 1983)     

Photoinduction of Spore Germination in a Fern, Mohria caffrorum

Irradiation of spores of the fern Mohria caffrorum Sw. witheither red light (67.4 µW cm^–2) or far-red light(63.2 µW cm^–2) for a period of 24 h induced maximumlevels of germination. Brief irradiations with blue light (127.6µW cm^–2) administered before or after photoinductioncompletely nullified the effects of red or far-red light; however,with prolonged exposure to blue light, germination levels roseto near maximum. The similar effects of red and far-red lightin promoting spore germination makes the involvement of phytochromein this process questionable. Based on energy requirements,the promotive and inhibitory phases of blue light appear toinvolve independent modes of action. Mohria caffrorum, ferns, spore germination, photoinduction, phytochrome     

Effects of light quality on the circadian rhythm of leaf movement of a short-day-plant

Studies were made of the effects of blue, green, red and far-red (FR) light on the circadian rhythm of leaf movement of Coleus blumei × C. frederici, a short day plant. Under continuous illumination with blue light, there was a significant lengthening of the period of the rhythm to about 24.0 hr, as compared to 22.5 hr in continuous darkness. Under continuous red light, the period length was significantly shortened to 20.5 hr. Under continuous green or FR, the period length was not significantly different from the dark control. It was observed that under continuous FR illumination, the leaves tended to oscillate in a more downward position. Eight-hr red light signals were effective in advancing the phase of the rhythm as compared to a control under continuous green light. Blue light signals were effective in delaying the phase of the rhythm. FR light signals were ineffective in producing either delay or advance phase shifts. Far-red light did not reverse the effects of either red or blue light signals. On the basis of these results it is suggested, that pigments which absorb blue or red light, rather than phytochrome, mediate the effect of light on the circadian rhythm of leaf movement.