APPEARANCE AND DEVELOPMENT OF PHOTOSYNTHETIC ACTIVITIES IN WHEAT ETIOPLASTS GREENED UNDER CONTINUOUS OR INTERMITTENT LIGHT—EVIDENCE FOR WATER-SIDE PHOTOSYSTEM II DEFICIENCY AFTER GREENING UNDER INTERMITTENT LIGHT*

Abstract— Etiolated wheat seedlings are greened under continuous or intermittent light. Under continuous light the onset of photosystem II (PS II) activity appears after 4 h of illumination. Under intermittent light (1 ms flashes alternating with 15 min dark periods), PS II activity cannot be detected after 300–400 flashes, although the pigment composition and structural development of these plastids are similar to those observed after 4 h of continuous light. However, the appearance of PS II activity in isolated plastids can be observed in two different ways: (1) in vivo by exposing the seedlings to a short period of continuous light after the intermittent light; or (2) in vitro by addition to the isolated plastids of an electron donor for PS II, such as diphenylcarbazide. It is concluded that the intermittent light induces development of the electron transport chain from PS II to PS I, but that a deficiency occurs on the water-side of PS II.     

ON THE POLARITY OF GREENING IN PRIMARY LEAVES OF DARK AND LIGHT-GROWN SEEDLINGS OF Triticum aestivum*

Abstract— In primary leaves of four-day-old dark-grown wheat seedlings the capability to accumulate chlorophyll under white light is highest in the tissues of the apical region. It declines though, as the dark-grown seedling ages and the primary leaf grows longer. This decrease is lower in the basal than in the apical regions of a leaf, which results in an inverted polarity of the capability to accumulate chlorophyll If the seedlings are grown under continuous white light applied from four different directions, the high capability of greening observed in the apical tissues of young leaves stays at that level even in old seedlings: the polarity does not change during culturing. The saturation-level of greening is much higher in the tissues taken from the apical region of a primary leaf than in those from the basal region.     

THE EFFECT OF MONOCHROMATIC LIGHT ON TRANS-HEXADECENOIC ACID and CHLOROPHYLL ACCUMULATION IN ETIOLATED LEAVES OF VIGNA SINENSIS L.*

Abstract— Spectral sensitivities for C16 rranshexadecenoic acid accumulation in etiolated leaves of Vigna sinensis L. show two maxima, one in the blue and one in the far red, indicating a control by the high irradiance reaction. Spectral sensitivities are different for rranshexadecenoic acid and chlorophyll accumulation indicating that the biosynthesis of these compounds must not be obligatory linked.     

PROTEIN COMPOSITION OF SPINACH CHLOROPLASTS AND THEIR PHOTOSYSTEM I AND PHOTOSYSTEM II SUBFRAGMENTS*

Abstract— The proteins of spinach chloroplasts and their subfragments containing photosystem I and photosystem II, obtained by Triton X-100 treatment or French-pressure rupture, were separated by sodium dodecyl sulfate (SDS)-acrylamide electrophoresis at pH 7·0 in phosphate buffer. The individual protein bands were identified where possible by comparing them with known, isolated and characterized proteins from chloroplasts, and their molecular weights were determined. The protein composition of the chloroplast fragments were correlated to the functional properties of these fragments. Distinct patterns were obtained for photosystem I and photosystem II particles. The major protein of photosystem II is expressed in the 23 kilodalton range and photosystem I proteins seem to be clustered mainly in the 50–70 kilodalton range.     

ANTAGONISTIC EFFECTS OF RED AND FAR-RED LIGHTS ON THE STABILITY OF PHOTOSYSTEM II IN PEA LEAVES EXPOSED TO HEAT

Abstract— The presence of light during exposure of intact pea leaves to high temperature (40°C) protects Photosystem II (PSII) against inactivation, as indicated by the preservation of the maximal variable 685 nm chlorophyll fluorescence and the photosynthetic oxygen evolution. This photoprotection was observed (i) to be saturated at low fluence rates ( ca 10 W m^-2) and (ii) to be strongly dependent on the spectral characteristics of the light. It was specifically induced by red light (630–670 nm) whereas other wavelengths were much less protective. A strong antagonism between red and far-red lights was also observed, with PSII stabilization by red light being partially cancelled by additional far-red light.     

THE EFFECT OF RED AND FAR-RED LIGHT ON NUCLEIC ACID METABOLISM IN RYE SEEDLING SHOOTS

Abstract— The quantitative changes in the levels of RNA and DNA in shoots treated with red and/or far-red light are presented.
The results indicate that red light, but not far-red light, stimulated cell division. The changes in RNA are discussed in relation to the nature of the light treatment.     

EFFECT OF UVA AND BLUE LIGHT ON PORPHYRIN BIOSYNTHESIS IN EPIDERMAL CELLS*

Abstract— To study porphyrin biosynthesis in normal human keratinocytes and A431 cells derived from human epidermoid carcinoma, cultured cells were incubated with delta-aminolevulinic acid (ALA), the precursor of porphyrin synthesis, and accumulation of porphyrins was measured spectrofluorometrically. Both human keratinocytes and A431 cells accumulated porphyrins in a time-dependent and a dose-dependent fashion. Protoporphyrin was the predominant porphyrin accumulated by both cell types. Porphyrin accumulation was enhanced by Ca Mg ethylene-diaminetetraacetic acid, a ferrochelatase inhibitor, and the enhancement was reversed by the addition of iron, suggesting the utilization of iron by ferrochelatase. The effect of light on porphyrin accumulation was evaluated by exposing the ALA-loaded A431 cells to ultraviolet-A (UVA) and blue light radiation, followed by continued incubation with ALA for 2–48 h. There was an enhancement of porphyrin accumulation 2–48 h after the radiation as compared with nonirradiated controls. Consistent with this finding, ferrochelatase activity decreased in these cells at 24 h and 48 h. These data demonstrate that human keratinocytes and A431 cells are capable of porphyrin biosynthesis, and that exposure of porphyrin-containing A431 cells to light, which includes the Soret band spectrum, decreases the ferrochelatase activity, which is responsible, at least in part, for the further increase in porphyrin level.     

BLUE LIGHT INDUCED PHOTOTRANSFORMATION OF PHYTOCHROME IN THE PRESENCE OF FLAVIN*

Abstract— Irradiation of the P_r form of phytochrome in the presence of flavin mononucleotide (FMN) which absorbs the actinic blue light yields P_fr at a rate greater than that in the absence of FMN. The actinic blue light absorbed by FMN enhances the phototransformation of P_r via the energy transfer from the former to the latter. On the other hand, the photoreversion of P_fr was inhibited by the presence of FMN when illuminated with blue light. The lack of photo-enhancement of the reversion of P_r, by blue light suggests that the P_fr chromophore (acceptor) transition dipole is virtually perpendicular to the FMN transition dipole, as the result of a chromophore reorientation in the P_r→P_fr phototransformation. The fact that blue light absorbed by flavin preferentially enhances the forward phototransformation of phytochrome while inhibiting the reversion may have an important implication in the high irradiance responses in plants in terms of a preferential accumulation of P_fr by blue light excitation.     

GENETIC AND PHYSIOLOGICAL STUDIES OF THE EFFECT OF LIGHT ON THE DEVELOPMENT OF THE MOSS, PHYSCOMITRELLA PATENS

The germination of Physcomitrella patens spores only occurs when wet spores are exposed to light. Depending on their ripeness, spores require from 44 to 64 h illumination to bring about maximum germination. There is a lag period of about 15 h between the reception of sufficient light to elicit germination before germination can be observed. Wavelengths in the range 640–64080 nm are much more effective in inducing germination than longer or shorter wavelengths, but far-red reversal of red light induction of germination has not been demonstrated. Light also has very marked effects on protonemal and gametophore development. In darkness, only caulonemata are produced, and these grow negatively geotropically. No new gametophores develop but existing gametophores grow negatively geotropically, etiolate and bear only scale leaves. In light, chloronemata, as well as caulonemata are produced, the former grow positively phototropically, while the latter grow at right angles to the direction of light, and neither cell type is sensitive to gravity. In the light, gametophores grow positively phototropically, are indifferent to gravity, produce large leaves and do not etiolate. All these responses to light by protonemata and gametophores are shown by cultures growing in a 23 h dark/l h red light cycle, but if this red light treatment is followed by 15min far-red light, the effect of the red light is reversed, indicating an involvement of phytochrome in the mediation of these responses. Mutants showing abnormal growth in the dark have been isolated, as well as mutants having abnormal phototropic responses. The latter type has lost the phototropic response of both the protonemal cell types, as well as of gametophores, indicating that these different responses may share a common component.     

LIGHT-ABSORPTION AND ELECTRON-TRANSPORT BALANCE BETWEEN PHOTOSYSTEM II AND PHOTOSYSTEM I IN SPINACH CHLOROPLASTS

Abstract— The distribution of absorbed light and the turnover of electrons by the two photosystems in spinach chloroplasts was investigated. This was implemented upon quantitation of photochemical reaction centers, chlorophyll antenna size and composition of each photosystem (PS), and rate of light absorption in situ. In spinach chloroplasts, the photosystem stoichiometry was PSIIJPSII_α/PSII_β/PSI= 1.3/0.4/1.0. The number (N) of chlorophyll (a+b) molecules associated with each PS was N(PSII_α)/N(PSII_β)/N(PSI)=230/100/200, i.e. about 65% of all Chl is associated with PSII and about 35% with PSI. Light absorption by PSII in vivo is selectively attenuated at the molecular, membrane and leaf levels, (a) The rate of light absorption by PSII was only 0.85 that of PSI because of the lower rate of light absorption by Chl b as compared to Chl a (approximately 80% of all Chl b in the chloroplast is associated with PSII). (b) The exclusive localization of PSII_α in the membrane of the grana partition regions and of PSI in intergrana lamellae resulted in a differential “sieve effect” or “flattening of absorbance” by the photosystems in the two membrane regions. Due to this phenomenon, the rate of light absorption by PSII was lower than that of PSI by 15-20%. (c) Selective filtering of sunlight through the spinach leaf results in a substantial distortion of the effective absorbance spectra and concomitant attenuation of light absorption by the two photosystems. Such attenuation was greater for PSII than for PSI because the latter benefits from light absorption in the 700-730 nm region. It is concluded that, in spite of its stoichiometric excess in spinach chloroplasts, light absorption by PSII is not greater than that by PSI due to the different molecular composition of the two light-harvesting antenna systems, due to the localization of PSII in the grana, and also because of the light transmission properties through the leaf. The elevated PSII/PSI reaction center ratio of 1.7 and the association of 65% of all Chl with PSII help to counter the multilevel attenuation of light absorption by PSII and ensure a balanced PSII/PSI electron turnover ratio of about 1:1.     

THE MULTIPLE PIGMENT-PROTEINS OF THE PHOTOSYSTEM I ANTENNA*

A photosystem I (PS I) holocomplex was obtained from barley by ultracentrifugation of PS I-enriched stroma lamellae on sucrose gradients. Further solubilization with glycosidic surfactants followed by Deriphat-poly-acrylamide gel electrophoresis (PAGE) fractionated the holocomplex into its core complex (CC I) and individual light-harvesting I (LHC I) pigment-protein subcomplexes. The LHC I contains chlorophyll a, all of the chlorophyll A of PS I and xanthophylls but no carotenes. Sodium dodecylsulfate PAGE analysis of the subcomplexes shows that barley LHC I is composed of at least five apoproteins having sizes between 11 and 24 kDa. Isolation of a 17 kDa LHC Ic component by Deriphat-PAGE shows it to be a photosynthetic pigment-protein. Room-temperature absorption spectra indicate that LHC Ic is enriched in chlorophyll a in comparison to the LHC Ia and Ib components. The LHC Ic apoprotein is shown to be distinct from the subunit III and IV polypeptides of CC I. Analysis of PS I fractions obtained from sucrose gradients as well as from Deriphat-PAGE indicates that in higher plants an oligomeric structure of the PS I entity exists in vitro.     

THE EFFECT OF PROLONGED LIGHT EXPOSURE ON THE EFFECTIVENESS OF PHYTOCHROME IN ANTHOCYANIN SYNTHESIS IN TOMATO SEEDLINGS*

Abstract— The hypocotyl of the tomato ( Lycopersicon esculentum ) seedling synthesizes large amounts of anthocyanin if exposed to prolonged light. Single light pulses are totally ineffective. The involvement of phytochrome can be shown by light pulse treatments following a prolonged light exposure. It is predominantly the action of blue/UV light which leads to a high responsiveness of anthocyanin synthesis towards phytochrome. Moreover, the data suggest a phytochrome-independent action of blue/UV light, in particular of UV-B, on anthocyanin synthesis.     

THE EFFECT OF INHIBITORS AND UNCOUPLERS OF PHOTOSYNTHETIC PHOSPHORYLATION ON THE DELAYED LIGHT EMISSION OF CHLOROPLASTS*

Abstract— Measurements were made of the 3.7 msec delayed light emission of chloroplasts treated with a variety of agents which affect the rate of electron transport (Hill reaction) or photosynthetic phosphorylation. The presence of the electron acceptors ferricyanide or pyocyanine increased delayed light emission. Inhibitors of electron transport (3-(3,4-dichlorophenyl)-1, -1-dimethylurea or 1,10(ortho)-penanthroline) inhibited delayed light emission. The addition of a phosphate acceptor system inhibited delayed light emission. This inhibition was reversed by inhibitors of the phosphorylation reaction, e.g. Dio-9 or phlorizin. From these results it was concluded that the 3.7 msec delayed light emission probably occurs as a result of back reactions of intermediates in the coupled electron transport and photosynthetic phosphorylation systems.     

EFFECT OF BLUE LIGHT AND RED LIGHT ON THE CONTROL PEA LEAVES TO INCREASED FLUENCE RATES OF CHLOROPLAST ACCLIMATION OF LIGHT-GROWN PEA LEAVES TO INCREASED FLUENCE RATES

Abstract— We have investigated the possibility of the involvement of a blue light fluence-rate sensing photoreceptor in the light acclimation of chloroplast components in light-grown pea seedlings. Low lightgrown seedlings were acclimated for 2 days to either 20 or 200 μmol^m-2s-2 of white, blue-enriched, or broad-band red light. An increase in blue-enriched light fluence rate was more effective than that of red light in bringing about both inhibition of internode growth and the enhancement of the chlorophyll a/b ratio. Ribulose 1,5-bisphosphate carboxylase/oxygenase and cytochrome f protein levels, per unit cell, also increased more markedly (around two-fold) in response to an increase in blue light. The 23 kDa polypeptide of the oxygen-evolving complex and the light-harvesting chlorophyll d b protein of photosystem II apoprotein levels vaned under all wavelengths to a lesser extent, correlating with total protein levels or greening. These data are consistent with the hypothesis of a role for a blue photoreceptor in detecting low versus high fluence rate of light, and subsequently controlling the light acclimation responses. Nevertheless photosynthesis or other mechanisms of fluence-rate photoperception must also be involved.     

离子交换树脂吸附乙酰丙酸的动力学研究

研究了大孔弱碱性树脂D310对乙酰丙酸的静态吸附动力学特征.采用批式离子交换法,考察了树脂粒径、溶液浓度、搅拌速率、温度对交换过程的影响,并用动边界模型对乙酰丙酸的离子交换过程进行了描述..结果表明,离子交换过程的控制步骤为颗粒扩散控制,搅拌速率和反应温度对交换速率无显著影响,吸附速率随乙酰丙酸初始浓度的增加而升高.交换过程的反应速率常数k0为0.8315,反应级数n为0.5313,表观活化能Ea为9.504kJ/mol,并得到了动力学总方程式.     

THE INFLUENCE OF LIGHT ON THE NON-DIAPAUSE RELATED ASPECTS OF DEVELOPMENT AND REPRODUCTION IN INSECTS

A literature review was undertaken to evaluate the effects of light on larval development and adult reproduction excluding diapause. Shortening or lengthening of larval developmental time, adult emergence, gametogenesis, fecundity and oviposition are all affected by both photoperiod and light quality.     

DEVELOPMENT OF THERMOLUMINESCENCE BANDS DURING GREENING OF WHEAT LEAVES UNDER CONTINUOUS AND INTERMITTENT ILLUMINATION

Abstract— Mature wheat leaves excited by 1-min illumination at a low temperature of -60° C showed five thermoluminescence bands at -45, -10, +25, +40 and +55° C (denoted as Z_u, A, B₁ B₂ and C bands, respectively). The development of these bands during greening of etiolated wheat leaves under continuous and intermittent illumination was investigated, and the following results were obtained. (1) Etiolated leaves showed only the C band. When these leaves were greened under continuous light, the B₁ and B₂ bands appeared at 3 h and the Z_u band appeared at 10 h. The B₁ and B₂ bands were intensified during prolonged greening under continuous illumination to be the strong bands observed for mature leaves. The A band and the group of B₁ and B₂ bands were alternative: Similar experiments by excitation of thermoluminescence at -20° C showed the development of the A band instead of these B₁ and B₁ bands. (2) When the etiolated leaves were greened under intermittent illumination (1-ms light + 5-min dark), the Z_u band first appeared after 5 h of illumination (60 flashes) and was gradually intensified during further illumination with 340 flashes but, interestingly, neither the B₁ nor the B₂ band appeared even after 24–28 h of illumination with 280–340 flashes. (3) On exposure of such leaves greened under intermittent illumination to continuous light, the B₁ and B₂ bands were rapidly developed. The appearance of these bands was accompanied by the generation of the Hill activity (DCIP photoreduction with water as electron donor). (4) These results were discussed in relation to the previous study on photoactivation of the latent water-splitting system accumulated in the leaves greened under intermittent illumination. It was deduced that the structure responsible for the A band or the group of B₁ and B₂ bands is involved in the evolution of oxygen in chloroplasts, and probably involves cations of the Mn²⁺ catalyst generated by the action of light.