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 spectrum of negative phototropism in Boergesenia forbesii

The rhizoid of Boergesenia forbesii, a gigantic unicellulargreen alga, exhibited negative phototropism. The bending processat 32?C followed Weber-Fechner's law and Bunsen- Roscoe's law.The minimum light energy inducing the phototropic bending was30 J.m^–2 at 467 nm and 32?C. The action spectrum of thisnegative phototropism had two distinct peaks at 380 and 443nm, with shoulders at 430 and 470 nm and a trough around 410run. Light of wavelengths longer than 502 nm was ineffective.The structure of the spectrum agrees well with that reportedfor the positive phototropism of Avena coleoptiles and otherplant parts. (Received February 24, 1979; )     

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; )     

Negative Phototropism in Vaucheria terrestris Regulated by Calcium I. Dependence on Background Blue Light and External Calcium Concentration

In the presence of 1–8 mM Ca²⁺ unilateral 10–15min irradiation with blue light can elicit negative phototropicbending in the tip-growing coenocytic fresh water alga, Vaucheriaterrestris (Xanthophyceae), when it is simultaneously irradiatedwith strong blue or green background light. By changing wavelength,fluence rate, and duration of background light and holding thoseof unilateral light (456 nm, 1.7 Wm^–2) negative phototropicresponse was analyzed: the wavelength of the background lighthad to be shorter than 540 nm; red light (660 nm) was ineffectiveeven at very high fluence rates (100W.m^–2). The negativebending was strongly and specifically dependent on the externalCa²⁺ concentration. Other divalent cations, Mg²⁺ and Ba²⁺, wereeither toxic or quite ineffective; Sr²⁺ could partly supportthe growth, but mediated neither positive nor negative phototropicbending. The rate of tip-growth was not significantly alteredbetween 10⁶M and 10^-6 mM Ca²⁺. Pre-irrradiation with the backgroundlight slightly increased the negative curvature; whereas thatwithout subsequent simultaneous irradiation does not cause negativebending, but rather increases the positive curvature. Three-mindelayed start of background light did not cause negative bendingany more. The present results strongly suggest that blue light elicitsan influx of Ca²⁺ at the apex of Vaucheria and that the increasedcytoplasmic Ca²⁺ regulates the sensitivity and direction ofphototropic response. (Received June 23, 1988; Accepted September 7, 1988)     

Phototropism in Vaucheria geminata II. The mechanism of bending and branching

The mechanism of phototropic bending and branching in Vaucheriageminata was analyzed. Using the half-side-illumination methodit was shown that phototropic bending is initiated by the formationof a new growth center on the illuminated side of the apicaldome of the tube, not by the difference in growth rate betweenthe lighted and shaded sides of the tip. Branching was alsoinitiated when the part proximal to the apical dome was illuminated.Blue light was effective for branching as it was for phototropicbending. The refractive indices measured at the growing tipand an area other than the tip were 1.36 and 1.34 respectively.A hyaline patch resembling the hyaline cap, which appeared priorto the onset of tip-growth in the apical dome, was invariablyformed shortly before the initiation of a new branch at theilluminated locus. (Received December 20, 1974; )     

Phototropism of Thalli and Rhizoids Developed from the Thallus Segments of Bryopsis hypnoides Lamouroux

Newly regenerated thalli were used to study the phototropism of Bryopsis hypnoides Lamouroux under different qualities of light. Positive phototropism in the thalli and negative phototropiam In the rhizoida of B. hypnoides were investigated and analyzed in terms of bending. Both thaiii and rhlzoids developed from thallus segments exhibited typical tip growth, and their photoreceptive sites for phototroplam were also restricted to the apical hemisphere. The bending curvature of rhizoids and thalli were determined with unilateral lights at various wavelengths and different fluence rates after a fixed duration of Illumination. The trends of bending from the rhizoid and thallus were coincident, which showed that the action spectrum had a large range, from ultraviolet radiation （366.5 nm） to green light （524 nm）. Based on the bending curvatures, blue light had the highest efficiency, while the efficiency of longer wavelengths （〉500 nm） was significantly lower. External Ca^2＋ had no effect on the bending curvature of thalli and rhlzolda. Blue light （440 nm） induced thallus branching from rhizoids, while red light （650 nm） had no such effect. Fast-occurring chloroplast accumulation In the outermost cytoplasmic layer of the blue light （440 nm）-Irradiated region In the rhizoid was observed, from which protrusions （new thalli） arose after 4 h of the onset of illumination, and this action was thought to be driven by the dynamics of actin microfilamenta.     

Negative Phototropism in the Rhizoid of Bryopsis plumosa

Negative phototropism in the rhizoid of Bryopsis plumosa wasanalyzed. The growth zone of the rhizoid was confined to theapical hemisphere, as is typical of tip growth. Upon unilateralillumination, the rhizoid bent away from the light source witha "bulging" manner. The photoreceptive site for phototropismwas also restricted to the apical hemisphere. The action spectrumfor this negative phototropism was determined from fluence-responsecurves that were obtained after fixing the duration of illuminationat 60 min and varying the fluence rate between 0.1 and 3.0 Wm^-2. The action spectrum had a large peak at 467 nm and smallerpeaks at 378 and 414 nm, resembling the action spectra of certainother blue-light responses. (Received November 29, 1995; Accepted May 29, 1995)     

Rhizoid differentiation in Spirogyra I. Basic features of rhizoid formation

Several types of rhizoids occurring in the process of differentiationin Spirogyra sp. are described and their interrelation was elucidated.There are two differentiation sequences: P_pPRh_ros or PpPRh_rodRh_ros(for explanation of abbreviations see p. 533), although undersome conditions the sequences ceased halfway through. The initiationtime for rhizoid formation had no relation to the cell cyclestage. The difference in growth patterns between the rhizoidand ordinary filament cells was demonstrated with Calcofluor-stainingand centrifugation. The optimum temperature and pH of the culture medium for rhizoiddifferentiation were 20?C and pH 7, respectively. A contactstimulus was not necessary for induction. Of the several environmental factors examined, light was themost important, for rhizoid formation, since a rhizoid was inducedonly when light was given after cutting the filament. (Received December 14, 1972; )     

Effects of temperature and light on the population dynamics of the Asterionella-Rhizophydium association

Growth parameters of the diatom Astenonella formosa Hass, andits fungal parasite Rhizophydium planktoniacum Canter emend,were measured at five temperatures and six light intensitieswith a 15?9 h light:dark cycle, using laboratory cultures ofboth organisms. With the parameter values obtained, thresholdhost densities were calculated in order to estimate the effectsof light and temperature on survival and epidemic developmentof the parasite The uninfected host reached light-saturatedgrowth rates between 0.917 day^–1 at 21?C and 0 285 day¹at 2?C. Under light limitation the optimum growth temperaturefor Asterionella decreased because of a reduced growth efficiencyGrowth inhibition at high irradiances was only observed at 2?CThe parasite reached the highest zoospore production at 2?Cand saturating irradiances: 30 2 zoospores per sporangium. Thisvalue was consistently reduced by lower irradiances and highertemperatures to only 2.2 zoospores at the opposite light andtemperature extremes Low light conditions depressed also theinfectivity of the zoospores At very low irradiances, they becamecompletely uninfective The light dependence of zoospore productionand infectivity was restricted to light intensities that limitedthe growth rate of the host. The development time of the sporangiaand the mfecti ve lifetime of the zoospores were not affectedby light but only by temperature, and ranged from 19.0 and 121 days respectively at 2?C to 1.9 and 2 1 days at 21?C- Theseeffects result in optimal conditions for the development ofa Rhizophydium epidemic at 11?C and a moderate light limitationof Astenonella At temperature above 7?C, the possibilities forepidemic development are only slightly affected by light andtemperature, except for very low irradiance levels, when thezoospores of the parasite become uninfective. However, below5?C the development of an epidemic is only possible at limitinglight levels. Conditions for survival of the parasite at lowhost densities are optimal at low temperatures and high irradiancelevels     

Diurnal Modulation of Arginine Decarboxylase Activity of Chenopodium rubrum L. by Temperature and Light

Arginine decarboxylase (ADC), one of the key enzymes of polyaminemetabolism in plants, was investigated in Chenopodium rubrumL. seedlings under constant and alternating temperature andlighting conditions. With seedlings grown at constant temperature,ADC activity of the whole seedling increased rapidly betweenthe second and the third day after sowing. This effect was alwayshigher under continuous light than in continuous darkness. Fromthe third to the seventh day after sowing, there was a markeddecrease in ADC activity of the whole seedling almost down tothe level of the second day. Under "normal" lighting and temperatureconditions (32.5?C/10?C, light/dark) there was a marked increasein ADC activity when plants were transferred to 10?C and a rapiddecrease when they were transferred to 32.5?C. The same timecourse was observed when an "inverse" light-temperature program(32.5?C/10?C; dark/light) was applied. This means that the timecourse of ADC activity in the seedlings is slightly light-dependent,but strongly temperature-dependent. The data are discussed withrespect to the chronopathological effects of the "inverse" light-temperatureprogram. (Received March 5, 1985; Accepted October 2, 1985)     

Growth and Dormancy in Lunularia cruciata (L.) Dum.: IV. LIGHT AND TEMPERATURE CONTROL OF RHIZOID FORMATION IN GEMMAE

The first sign of initiation of growth in dormant gemmae ofL. cruciata is the formation of rhizoids. Gemmae in the cupcannot ‘germinate‘ until exposed to substrate conditionsallowing the outward diffusion of a growth inhibitor. Rhizoidproduction depends on temperature and light. With long lightperiods rhizoids are formed over a wide range of temperatures.Transference to darkness after 2 h white light causes about50 per cent of gemmae to produce rhizoids, and these are formedonly between 20 and 25 °C. Outside these temperature limitsthe percentage of gemmae with rhizoids soon drops to zero. Althoughrhizoid production is prevented in total darkness, gemmae remainalive for well over 6 months. Red light for as little as 5 spromoted, and far-red light inhibited, rhizoid formation inthe dark. Coumarin and indol-3yl-acetic acid can substitutefor light and partly reverse the effect of far-red irradiation.     

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)     

Culture of chlorophyllous tobacco-cells not requiring any organic additives except sucrose in the medium I. Effects of light and temperature on the growth of the cells

1. In the dark, HNG (habituated Nicotiana glutinosa) and NG cellsscarcely grew at 15?C, and the difference between the growthrates of HNG and NG was small at both 15?C and 25?C.
2. The stimulatoryeffect of light (4000 lux) on the cell growthrate was higherat 25?C than at 15?C for both HNG and NG.
3. Light exerted muchmore effect on the growth rate of HNG thanof NG.
4. The thermaleffect was higher in the light than in the darkfor both HNGand NG, and was somewhat greater on NG than onHNG.
5. The synergisticeffect of light and temperature on cell growthwas greater onHNG than on NG.
6. HNG contained more chlorophyll than NG.
7. Inaddition, there was little difference between the friabilitiesof cell groups of HNG and NG.

(Received December 3, 1976; )     

Effect of High-intensity Light Given Prior to Low-temperature Treatment on the Long-day Flowering of Pharbitis nil

Pharbitis nil, strain Violet which had been exposed to high-intensitylight (18,000 lux at 23?C) for 7 days followed by a low-temperaturetreatment (13–14?C) for 7 days initiated flower buds evenunder continuous light, but plants given these treatments inreverse order failed to bud. Three days of high-intensity lightat 23?C was most effective in promoting the flower-inducingeffect of the subsequent low-temperature period. Six days oflow temperature following the 3-day high-intensity light periodinduced near-maximum flowering response. DCMU (5?10^–6M) given during the high-intensity light period inhibited flowering,but when given during or after the low-temperature period itwas ineffective. DCMU at the same concentration given before,during or after an inductive 16-hr dark period at 26?C did notinhibit flowering. Sucrose, ATP, NADPH and some other reducingagents tested did not nullify the DCMU effect nor substitutefor the effect of high-intensity light. But, the high-intensitylight effect could be substituted, at least partly, by 5-chlorosalicylicacid, 3,4-dichlorobenzoic acid and some other benzoic acid derivatives,which are highly effective in inducing long-day flowering inthe short-day plant, Lemna paucicostata. (Received October 20, 1981; Accepted February 3, 1982)     

Response to Temperature in a Stand of Pearl Millet: VI. LIGHT INTERCEPTION AND DRY MATTER PRODUCTION

Stands of pearl millet were grown in glasshouses in which meanair temperature was controlled to 19, 22, 25, 28 and 31 ?C withan amplitude of ?5 ?C. During the main growth period, leaf areaindex increased at a constant rate which was proportional tomean temperature above a base of 10 ?C. The warmest stand, therefore,intercepted more radiation before anthesis but the transmissioncoefficient was independent of temperature (K 0.3). Based ondry weight at final harvest, the efficiency of conversion forintercepted radiation ranged from about 2.1–2.4 g MJ^–1consistent with field experience. Combining this informationwith figures for the duration of growth in relation to temperaturesuggests that growth rate should be maximal at 25–27 ?Cand total dry weight at 20–22 ?C. Key words: Temperature, Pearl millet, Growth rate, Light     

The Influence of Stress Conditions on Chlorophyll Content of Two Range Grasses with Contrasting Photosynthetic Pathways

The influence of various treatments and temperature regimeson total chlorophylls and on the chlorophyll a:b ratio of westernwheatgrass and blue grama plants was investigated at differenttime intervals during the 120-day growth period. Western wheatgrass,a C₃ species, accumulated greater amounts of chlorophyll thandid blue grama plants, a C₄ species. Maximum concentrations(mg gd wt^–1) of chlorophylls in western wheatgrass andin blue grama were recorded at the lower (13/7°C) and higher(30/18°C) temperature regimes. Nitrogen fertilizer alonedecreased the chlorophyll content in both species. The chlorophylla:b ratio in blue grama ranged from an average of 2·00under irrigated plus fertilized conditions to 3·00 undercontrol and fertilized conditions. On the other hand, the chlorophylla:b ratio in western wheatgrass remained constant at 3·00throughout the growing season under various treatments and temperatureregimes.     

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.     

Negative phototropic response of rhizoid cells in the fern Adiantum capillus-veneris

In general, phototropic responses in land plants are induced by blue light and mediated by blue light receptor phototropins. In many cryptogam plants including the fern Adiantum capillus-veneris, however, red as well as blue light effectively induces a positive phototropic response in protonemal cells. In A. capillus-veneris, the red light effect on the tropistic response is mediated by phytochrome 3 (phy3), a chimeric photoreceptor of phytochrome and full-length phototropin. Here, we report red and blue light-induced negative phototropism in A. capillus-veneris rhizoid cells. Mutants deficient for phy3 lacked red light-induced negative phototropism, indicating that under red light, phy3 mediates negative phototropism in rhizoid cells, contrasting with its role in regulating positive phototropism in protonemal cells. Mutants for phy3 were also partially deficient in rhizoid blue light-induced negative phototropism, suggesting that phy3, in conjunction with phototropins, redundantly mediates the blue light response.     

Initiation of Rapid Ethylene Synthesis by Apple and Pear Fruits in Relation to Storage Temperature

The influence of storage temperature on the onset of rapid ethyleneproduction was investigated for fruits of Conference pear (Pyruscommunis L.) and five cultivars of apple (Malus domestica Borkh.).The time taken from harvest to rapid ethylene production wasshorter and more uniform at 3 ?C than at 18–20 ?C forConference pears and Golden Delicious apples. Increases in internalethylene concentration, 1-amino cyclopropane-1-carboxylic acidconcentration and ethylene production were simultaneous in GoldenDelicious apples at 3 ?C. When Golden Delicious apples wereheld at 3 ?C for 48 h and then kept at 20 ?C the mean time ofonset of ethylene production was similar to that for applesheld continuously at 20 ?C. However, two periods of 48 h at3 ?C caused earlier ethylene production. Conversely, ethyleneproduction at 3 ?C was delayed by transfer to 20 ?C for twoperiods of 48 h. Cox's Orange Pippin and other apple cultivarstended to show more synchronous ethylene production at 3 ?Cthan at higher temperatures but the mean time of onset was eitherunaffected by temperature or slighdy delayed at lower temperature.Acceleration of the onset of ethylene production by low temperaturewas never observed in Cox's Orange Pippin apples harvested atweekly intervals from 10 August to 17 September. Key words: Ethylene, Storage temperature, Pyrus communis, Malus domestica     

Effects of temperature on the cytokinin requirement of tobacco calluses

A cytokinin-nonrequiring strain (T22) was isolated from a cytokinin-requiringcallus strain T2 of tobacco (Nicotiana tabacum var. Bright Yellow). Strain T22 grew rapidly on the medium without added kinetinat 26?C. But its growth was completely suppressed at 16?C. Thisgrowth suppression at 16?C was partially recoverable by supplyingkinetin. Benzyladenine, geranylaminopurine and 2-methyl-8-benzylamino-s-triazolo[l,5-a]pyrazinewere also effective in removing growth suppression at 16?C.Adenine, which was unable to remove growth suppression of T22at 16?C, promoted the growth of T2 at 26?C, but not at 16?C.Physiological differences between cytokinin-requiring and -nonrequiringcalluses are discussed. ¹Part II in the series "Studies, on Plant Tissue Cultures";for Part I, See Plant & Cell Physiol. 9: 103–114 (1968). (Received May 29, 1970; )