Beginning Of Illumination Research Articles

Fast induction of translatable mRNA by blue light in neurospora crassa wt: The wc-1 and wc-2 mutants are blind

After blue-light irradiation of Neurospora crassa ( wt) mycelia we observed an increase of about 13 translatable mRNA species within a period of 30 min. The induction of translatable mRNA species followed a specific temporal pattern which permitted the identification of four distinct classes. One of the translatable mRNAs was induced in less than 2 min, while the others showed lag periods of 5, 10 or 20 min from the beginning of illumination. The white collar mutants, wc-1 and wc-2, which do not display any of the blue-light-induced physiological effects tested until now were found to be defective for the photoinduction of translatable mRNAs.

Photomorphogenesis in Physarum polycephalum

Photo-induced fruiting-body formation of the slime mold Physarum polycephalum can be divided into two stages. The first stage (I) starts with the beginning of illumination (0 h) and ends with the formation of nodules (12 h). The second stage (II) is characterized by culmination, sporangiophore formation and melanization of sporangiophore heads (13-17 h). We investigated the expression of actin, alpha- and beta-tubulin during this differentiation process using Northern blot analysis and run-off transcription in isolated nuclei. Whereas actin mRNA is irreversibly lost during stage I, we observed two peaks in mRNA concentration for alpha-tubulin and one peak for that of beta-tubulin during stage I and a coordinated alpha/beta-tubulin mRNA induction during stage II. Stage II induction appears to be related to a presporangial mitosis. Transcriptional activity of the three genes studied shows two maxima, namely one in the middle of stage I and the other at the end of stage II. Our data suggest that the expression of the three cytoskeletal proteins investigated follows a distinct temporal pattern comprising changes in both mRNA synthesis and decay. We also propose a novel function of tubulin in Physarum which is not related to mitosis.

Two Components of Light-Induced Photoconductivity Decays in a-Si:H

This paper reports the sample dependence of light-induced photoconductivity σph decays in glow-discharge a-Si:H films. “Device-grade” and lightly-P-doped samples both displayed a fast σph decay component at the beginning of illumination, and a subsequent slow one. “Defective” samples, on the other hand, only showed a slow component. A combined measurement of the σph light intensity dependence γ revealed that the fast component is accompanied by a rapid change in γ. These results are discussed on the basis of a simplified model which assumes two distinct recombination processes, i.e., the process from band to tail and the process through dangling bonds.

Induction of size reduction in Escherichia coli by near-ultraviolet light.

Escherichia coli AB1157 cells, growing exponentially at 37 degrees C in 63B1 medium (supplemented with glucose and casamino acids) with a doubling time of 50 min, were subjected to continuous illumination with 366-nm light at a fluence of 1.5 kJ . m-2 X min-1. Under these conditions, the growth rate decreased and after 1 h of illumination, a new stable exponential mode was reached with a doubling-time of 73 min. This reduction in growth rate occurred without any change in the rate of cell division for two generations after the beginning of illumination. Survival was unaffected, implying that cell size must have decreased. This was confirmed with size distribution curves of control and illuminated cells obtained with a Coulter counter. Furthermore electron micrographs of negatively stained cells indicated that illumination results in a 30-40% decrease in cell length, the diameter increasing by 8%. Hence 366-nm light uncouples growth and division rates. Illumination under the above conditions triggered the accumulation in vivo of 8-13-linked tRNA. The stationary level of the 8-13 link, 80% of the maximal level, was reached precisely when the growth rate reached its new stable value. Furthermore, no reduction in growth rate occurred in a nuv- cell lacking 4-thiouridine in its tRNAs. Hence we conclude that the 366-nm photons trigger partial tRNA inactivation with consequent slowing down of protein synthesis and accordingly of the cell growth rate. In addition, the stringent response has at most a minor effect. In conclusion, near-ultraviolet light is able to decrease the rate of cell growth by restricting the availability of charged tRNAs, and this occurs without affecting the cell division rate.

Diurnal and circadian rhythmicity in the expression of light-induced plant nuclear messenger RNAs

The levels of nuclear mRNAs for three light-inducible proteins (light-harvesting chlorophyll a/b protein, small subunit of ribulose-1,5-bisphosphate carboxylase and early light-induced protein) have been analyzed under light-dark and constant light conditions. The levels of all three mRNAs have been found to vary considerably during the day, both under ligh-dark and under constant light conditions, demonstrating the existence of diurnal and circadian rhythmicity in the expressionoof these nuclear-coded plant proteins. The levels of two of these mRNAs have been found to be enhanced 2 h before the beginning of illumination when active phytochrome levels are still low.

Factors affecting the development of the capacity for ATP formation in isolated chloroplasts

Full development of the capacity for ATP formation in isolated thylakoid membranes coincides with the beginning of illumination. Indeed, the yield of ATP per ms of illumination is about twice as great during the first 15 ms of high-intensity illumination as it is thereafter. The presence of valinomycin and K + prevents the formation of a membrane potential (as indicated by the obliteration of most of the change in absorbance at 518 nm) and at the same time delays the formation of the capacity for ATP synthesis for many milliseconds. Presumably, phosphorylation is initially dependent on a rapidly formed membrane potential, whereas after a delay a ΔpH sufficient to drive ATP formation forms. The actual duration of this delay depends on the phosphoryl group transfer potential (i.e., ΔG ATP) of the ATP-synthesizing reaction. If the delay in the presence of valinomycin and K + represents the time required to develop a ΔpH capable of driving phosphorylation by itself, then the effect of ΔG ATP on the duration of the delay suggests that the onset of phosphorylation is determined by the magnitude of the electrochemical potential of protons and not by factors affecting the activation of the coupling factor enzyme. The initial ATP formation, which is almost entirely dependent on the electrical potential, should not be affected by the electrically neutral exchange of cations catalyzed by nigericin. When the external pH is 7.0 this seems to be true, since the ATP synthesis which is initially sensitive to valinomycin and K + is largely insensitive to nigericin and K +. However, when the external pH is 8.0 the response to nigericin is exactly the opposite and the ATP formation which is sensitive to valinomycin is also abolished by nigericin. These data suggest that there may be either an energetic requirement for both a ΔpH and membrane potential at alkaline pH or a non-energetic requirement for a minimum proton activity in the initiation of phosphorylation.

CO2-Fixierung während cler Photosynthese-Induktion von Synechococcus.

Kinetics of CO 2 exchange and 14 C-incorporation into water soluble products were studied during photosynthetic induction period of Synechococuss ( Anacytis nidulans , strain L 1402-1). In 0.03 and 3 vol.-% CO 2 at + 35°C under low light grown cyanobacteria were harvested mainly during the exponential growth phase. Experiments were carried out in low CO 2 concentration (0.03vol.-%). Aged cultures showed after maximum in photosynthetic CO 2 uptake a very low rate after 8 min. Under these conditions radioactivity was found mainly in glutamate, aspartate and glycine/serine. Under the influence of iodacetamide (0.001 and 0.01 M) only a maximum of CO 2 uptake at the beginning of illumination and a CO 2 outburst after preillumination, measured with an infrared gas analyzer, could be observed. In Synechococcus cells treated with 0.01)[iodoacctamide (3/4 h) 14 CO 2 , was incorporated into aspartate only. 0.001 M iodacetamide reduced 90 % of the activity of ribulose- 1,5-bisphosphate carboxylase and ribulose-5-phosphate kinase. The inhibitory effect on fructose-l,6- bisphosphate (8%), phosphoenolpyruvate carboxylase (18%) and glyceric aldehydephosphate dehydrogenase (36%) was relatively low. CO 2 concentration (0.03 or 3 vol.-%) during growth had no effect on activity of fructose-l,6-bisphosphate, ribulose-5-phosphate kinase and ribulose-l ,5-bisphosphate carboxylase. Increasing temperatures during growth ( + 15, + 25 and +35°C) caused an increase in activity of phosphoenolpyruvate carboxylase and a decrease of ribulose-l,5-bisphosphate carboxylase. lnvestigating other enzymes we found a high phosphoenolpyruvate carboxykinase activity, a low level of NAD+ specific malic enzymes and of NADPH malate dehydrogenase. Our data are very similar to the phosphoenolpyruvate earboxykinase type of C 4 plants. In short term kinetics experiments (2 rhythm) aspartate was the first labelled product. Our findings point at the important role of phosphoenolpyruvate carboxylation during photosynthetic induction period. In other series of experiments feeding ferredoxin an increased photosynthetic CO 2 uptake during dark/ light transients was detected.

Photosynthetic apparatus in chilling-sensitive plants

Changes in the levels of both ATP and protein in relation to Hill reaction activity following cold and dark storage and illumination of leaves of Lycopersicon esculentum Mill. were studied. Loss of Hill reaction activity observed during cold and dark storage of leaves for 3-4 days was accompanied by about 50% decrease of both ATP and protein levels while the content of chlorophyll was not affected Illumination of cold and dark stored leaves (8000 lx for 2 h) resulted in almost a complete restoration of both ATP and protein levels as well as Hill reaction activity. The latter process proceeded, however with different kinetics than the former ones. The rate of Hill reaction activity increase very rapidly from the beginning of illumination while the ATP level diminished during the first hour of illumination. In addition there was a lag in the increases in protein content. By about two hours of illumination all these processes reached the maximum values. Following illumination of leaf dises stored in the cold and dark in the presence of either cycloheximide or DCMU, both ATP and proteins levels as well as Hill reaction activity were greatly diminished. These data seem to suggest that the lack of reactivation of Hill reaction activity in the presence of these two inhibitors is due to inhibition of ATP synthesis required primarily for manganese reincorporation into the thylakoid membrane and theraby restoration of Hill reaction activity (Kaniuga, Zabek and Sochanowicz, Planta 1978b). Contribution of cytoplasmic protein synthesis in this process appears to be of secondary importance, although the inactivation and reactivation of electron transport are accompanied by a large loss (as high as 50%) and the restoration of the initial protein content in leaves following illumination.

Numerical analysis of pulsating evaporation of condensed matter under the action of laser radiation

A simple model is used in analysis of pulsating evaporation observed during interaction of laser radiation with the surface of an absorbing substance. The pulsations are due to the instability of the metastable state of an overheated liquid phase. Explosive breakup of the metastable phase is described as the appearance of a new evaporation front at the moment when the temperature reaches the overheating limit. A numerical solution of the boundary-value problem of heat conduction in the region of the moving front shows that, according to this model, the process of establishment of the pulsation period is nonmonotonic: the shortest interval is between the first and second explosions after the beginning of illumination.

Ultrastructural Effects of Water Stress on Chloroplast Development in Jack Bean (Canavalia ensiformis [L.] DC)

An ultrastructural study has been made to determine to what degree chloroplast differentiation is retarded in leaves of young jack bean (Canavalia ensiformis [L.] DC.) seedlings when they are subjected to mild water stress. Rapid chloroplast differentiation occurred when etiolated seedlings were allowed to green at relative humidities above 85% but not at a relative humidity of 25%. Response to a drop in humidity was rapid. Germination and early development in the dark occurred at 100% relative humidity. At the time of exposure to light, the etioplasts contained well formed prolamellar bodies. Under high relative humidity conditions, transformation of the prolamellar body was well advanced within 2 hours. Under low relative humidity conditions, however, prolamellar body differentiation was extremely retarded for more than 24 hours following the beginning of illumination.

PLASTID DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS

SummaryFor 14‐day‐old dark‐grown beans a quantitative study of plastid membrane formation has been made for light‐induced chloroplast development in the primary leaves. During the first 10 h of illumination, thylakoid formation resulted from the rearrangement of the membranes of the prolamellar body. De novo thylakoid formation commenced between 10 and 15 h after the beginning of illumination and resulted, in the course of 160 h of illumination, in a ten‐fold increase in thylakoid membrane. During the course of greening no cell division occurred in the mesophyll cells, plastid expansion took place in all of the mesophyll cells but plastid division only occurred in the spongy mesophyll cells to result in an 11 % increase in the plastid number of the whole leaf during the first 18 h of illumination.When leaves were supplied with d‐threo‐chloramphenicol during greening there was a severe inhibition of thylakoid formation, vesicles were formed in the plastid stroma and rather fewer and larger grana than normal were produced. However, the proportion of thylakoid material in grana was normal. As l‐threo‐chloramphenicol yielded exactly normal chloroplasts it is concluded that thylakoid synthesis was inhibited by d‐threo‐chloramphenicol by the inhibition of the synthesis of one or more thylakoid proteins on the 708 ribosomes of the plastids.

Der Einfluß von Licht auf Wachstum und Abscisinsäuregehalt der Erbsenwurzel

Roots of pea seedlings, growing in a water culture, were illuminated by white fluorescent lamps. One or two weeks after the beginning of illumination, the roots were analysed morphologically, the content of endogenous abscisic acid (ABA) was determined by means of gas liquid chromatography, and the results were compared with those of control roots growing in the dark. It could be demonstrated that in most cases light causes an inhibition of longitudinal growth of the roots. The absolute number of lateral roots decreased, however, in relation to the length of the main root, the number of laterals was increased one week after illumination. The diameter of roots growing in the light was greater than the diameter of the controls (dark-grown roots). The quantitative determination of the abscisic acid content showed that light causes a marked increase of the ABA-concentration in roots: Since application of synthetic ABA (Tietz 1973) causes similar effects as the illumination of roots, it is concluded that ABA is at least partly involved in the light-dependent morphological changes of root growth.

Effect of thyroxine on nervous system in controlling chicken heart rate

Diurnal heart rate rhythm was determined continuously by radiotelemetry in the chicken and the rabbit under unrestrained conditions. Clear diurnal heart rate rhythm synchronized with illumination was observed in the chicken, but not in the rabbit. The birds were given single subcutaneous injections of 50 μg of l-thyroxine (T 4)/100 g body weight at 1700 (2 hr before darkness); an increase in heart rate occurred about 2 hr after injection and the effect lasted for 21 hr. Bovine thyrotropin (TSH) at the same dose as T 4 was also injected subcutaneously at 1700. The TSH effect on heart rate started about 3 hr after injection and lasted for 9 hr. The T 4 effect on the rabbit heart rate was compared with that of the chicken. It was first observable at 24 hr after injection and lasted for 19 hr. When T 4 was administered at 0500 (beginning of illumination) in the chicken, the effect appeared 14 hr after injection and lasted for 10 hr (at night). Bilateral vagotomies destroyed the diurnal heart rate rhythm in the chicken. These results indicate that T 4 may modify function of the autonomic nervous system by decreasing vagal tone to the heart in the chicken.

SENSITIZED PHOTOOXYGENATION ACCORDING TO TYPE I MECHANISM (RADICAL MECHANISM) — PART III. EXPERIMENTS WITH CONTINUOUS ILLUMINATION

Abstract— The photochemical reaction in the system thionine (sensitizer), allylthiourea (ATU, acceptor), and oxygen was studied with continuous illumination. In oxygen‐free aqueous solution thionine is photoreduced to leucothionine. With oxygen, however, a photooxygenation of the acceptor takes place. At the same time the quantum yield of the bleaching reaction of thionine decreases markedly in comparison with that of the oxygen‐free solution. At about 100 sec after the beginning of illumination, the overall quantum yield of the bleaching reaction diminishes further because the leucothionine formed during the reaction now becomes transformed into thionine. The quantum yields do not change significantly over the range of oxygen concentrations studied (initial concentration 1 × 10‐5 to 5 × 10‐5M). In addition they are independent of the light intensity. The influence of the pH and the acceptor concentration were also investigated.The sensitizer is not only bleached reductively, but is also partly destroyed by oxidation. The results are in agreement with the reaction scheme elucidated by flash photolysis measurements.In accordance with this reaction scheme, the primary reaction (a) of the reductive bleaching of the sensitizer, (b) of the photooxygenation of the acceptor and (c) of the oxidative destruction of the sensitizer, is identical in all cases. This process is the redox reaction between the sensitizer triplet and the acceptor, where a semithionine and an ATU‐radical are formed. The reaction represents an example of a Type I photooxygenation according to the notation of Gollnick.

Photosynthesis, photooxidation of chlorophyll and fluorescence of normal and manganese-deficient Chlorella with and without hydrogenase

Growth, chlorophyll content, chloroplast structure, photosynthesis, photooxidation of chlorophyll and fluorescence were studied in normal and manganese-deficient, closely related Chlorella strains with hydrogenase (Chlorella vulgaris f. tertia 211-8k) and without hydrogenase (Chlorella vulgaris 211-8m).Under Mn-deficient conditions, algae with hydrogenase grow slowly for several weeks without becoming chlorotic and without any major change in thylakoid structure, whereas those without hydrogenase show a rapid loss of most of their chlorophyll, followed by a breakdown of thylakoid structure. In algae without hydrogenase, the inhibition of photosynthesis by Mn deficiency is much less pronounced when photosynthesis is determined on a chlorophyll rather than on a cell-volume or dry-weight basis. Thus the little remaining chlorophyll of these algae is photosynthetically much more active than the chlorophyll of the Mn-deficient, non-chlorotic algae with hydrogenase.Photooxidation of chlorophyll under pure O2 in very strong light is always accelerated by Mn deficiency.Only in algae containing hydrogenase is there under aerobic conditions a pronounced peak of fluorescence at the beginning of illumination. This is indicative of a high degree of reduction of Q, the primary electron acceptor of System II of photosynthesis. The fluorescence peak can be eliminated by either 1 min preillumination with far red (λ=717 nm) or by treatment in the dark for 1 hr with pure O2. In algae without hydrogenase, in contrast, fluorescence intensity at the onset of illumination is lower than the steady-state level, indicating an oxidized state of Q. In these algae a high start of fluorescence can only be produced by prolonged anaerobic incubation. These results indicate that even under aerobic conditions algal hydrogenase, or a biochemical system very closely associated with it, has some residual activity which enables it to feed electrons into System II of photosynthesis, thereby keeping Q in a reduced state with correspondingly high fluorescence at the beginning of illumination. In organisms without hydrogenase, in contrast, this can only be achieved by prolonged anaerobiosis. In addition, the presence of hydrogenase seems to protect the chlorophyll against photooxidative destruction when the cells are under Mn deficiency.

Études simultanées des cinétiques de fluorescence et d'émission d'oxygène photosynthétique

The kinetics of fluorescence induction in relation to O2 emission by Chlorella pyrenoidosa have been studied. At the beginning of illumination, one observes a short activation period during which the fluorescence intensity and O2 emission velocity increase simultaneously; this is followed by a longer phase when the fluorescence intensity continues to increase, whereas the velocity of O2 emission decreases. The variation of fluorescence intensity and the velocity of O2 emission are respectively parallel and complementary during the successive two phases. These relations, which are linear, can be explained only if the fluorescence is emitted essentially by the chlorophyll associated to the photochemical system evolving O2 (System II). Fluorescence kinetics measurements at the beginning of illumination have been carried out in the presence of inhibitors specific to O2 emission. The changes of fluorescence intensity observed during the initial (parallel) phase show an increase in the presence of inhibitors, whereas the complementary relation during the second phase is maintained. Kinetics comparable to those observed in the presence of inhibitors have been obtained at high light intensities and at low temperature (− 70°). The different factors disjoint the photochemical reaction from the thermal ones, thus preventing the regeneration of the photochemical complex. It is shown that all these results are coherent with the scheme proposed in the preceding paper for the interpretation of transient kinetics of O2 emission. Les cinétiques d'induction de fluorescence ont étéétudiées en relation avec l'émission d'O2 chez Chlorella pyrenoidosa. Au début de l'illumination, on observe une courte période d'activation pendant laquelle l'intensité de fluorescence et la vitesse d'émission d'O2 augmentent simultanément; cette période d'activation est suivie d'une phase plus longue pendant laquelle l'intensité de fluorescence continue à augmenter alors que la vitesse d'émission d'O2 décroit. Les variations de l'intensité de fluorescence et de la vitesse d'émission d'O2 sont respectivement parallèles et complémentaires pendant ces deux phases successives. Ces relations sont linéaires et peuvent s'expliquer seulement si la fluorescence est émise par la chlorophylle associée au système photochimique libérant l'O2 (Système II). On a étudié les cinétiques de fluorescence au début l'illumination en présence d'inhibiteurs spécifiques de l'émission d'O2. Les variations de l'intensité de fluorescence observées pendant la phase d'activation sont alors augmentées, tandis que la relation de complémentarité, valable pendant la seconde phase, est conservée. Des cinétiques de fluorescence comparables ont été obtenues aux fortes intensités lumineuses ou à basse température (− 70°). Ces différents facteurs découplent la réaction photochimique des réactions thermiques, empêchant ainsi la régénération du complexe photochimique. Ces résultats sont cohérents avec le schéma proposé dans l'article précédent pour l'interprétation des cinétiques transitoires d'émission de l'O2.

THE EFFECT OF GROWTH CONDITIONS AND THE STAGE OF LEAF DEVELOPMENT ON THE HILL REACTION IN HOMOGENATES OF PISUM SATIVUM LEAVES

Miller, John H. (Yale U., New Haven, Conn.) The effect of growth conditions and the stage of leaf development on the Hill reaction in homogenates of Pisum sativum leaves. Amer. Jour. Bot. 47(7): 532–540. Illus. 1960.—With plants grown under short‐day conditions (8 hr. light and 16 hr. dark), crude chloroplast suspensions from young leaves have a higher Hill‐reaction activity between 1 and 3 hr. after the beginning of illumination than suspensions from older leaves, while after 5–7 hr. of illumination, this activity difference is not found. These differences result from a marked diurnal rise and fall in the Hill reaction. The magnitude of the rise depends on the age of the leaf from which the chloroplast suspension is prepared. Peak activity occurs after the plants have received between 3 and 4 hr. of light and is highest in suspensions prepared from young leaves. Suspensions from the oldest leaves show no diurnal change in activity. No diurnal changes in activity are found in chloroplast suspensions from plants which are grown under continuous light, and the diurnal rise and fall is dependent on the plant receiving an alternation of light‐dark‐light.

Induction Phenomena of Photosynthetic Algae at Low Partial Pressures of Oxygen

The effect of a dark period at very low partial pressures of oxygen (10 −4 –10 −1 mm. Hg) upon the subsequent photosynthetic production of oxygen by Chlorella pyrenoidota with saturating intensities of illumination has been investigated. With the lowest partial pressures of oxygen used the time course of oxygen production separates into two phases; an initial burst followed by a subsequent rise to the final steady state. The separation of the two phases in time is greater the lower the concentration of carbon dioxide and the longer the preceding dark period. The initial burst of oxygen as distinct from the steady state production is not inhibited by 10 −3 M. iodoacetamide. In contrast with the ‘Hill’ reaction, as measured after addition of quinone, the initial burst of oxygen was inhibited by p -chloromercuribenzoate 10 −4 M.). Concentrations of sodium fluoride and of 2:4-DNP which had no effect on the steady state of photosynthesis shortened the half-time for attainment of the steady state so removing or obscuring the initial burst. The effect with fluoride was observed only if added at the beginning of the preceding dark period. It is suggested that the initial oxygen burst results from reductive amination and carboxylation of keto acids present at the beginning of illumination. Iodoacetamide is assumed to inhibit steady state photosynthesis by preventing reduction of phosphoglyceric acid (PGA) to triose and hence its regeneration. It is assumed not to inhibit reductive amination or carboxylation. With long dark periods the initial burst is separated in time from the final acceleration to a steady state; this phase appearing as a decreased rate of production of oxygen may be also due to inhibition by fermentation products or to their conversion to amino acid without change in oxidation-reduction. The separation in time is minimized if fluoride or 2:4-dinitro-phenol is added at the beginning of the dark period; both probably prevent accumulation of pyruvic acid during fermentation limiting the initial reactions to the reduction of PGA.