CHANGES IN THE RATES OF PHOTOCONVERSION OF PHYTOCHROME DURING ETIOLATION IN MUSTARD SEEDLINGS

Abstract— The relative phytochrome photoconversion rates in cotyledons and hypocotylar hook of etiolating mustard ( Sinapis alba L.) seedlings were measured between 16 and 96 h after sowing. It was found that at constant fluence rates photoconversion rate in red light increases in both organs with time whereas the photoconversion rate in far-red (756 nm) light decreases with time of development. Since the isosbestic point remains constant, it was concluded that the observed changes cannot be attributed to changes of extinction coefficients. It was not possible, however, to decide whether the observed changes are due to changes of light attenuation or quantum yields.     

LIGHT-INDUCED CHANGES IN THE VESICULAR APPARATUS OF Phycomyces SPORANGIOPHORES DURING THE PHOTOTROPIC RESPONSE

Abstract— We studied the ultrastructure of laterally illuminated stage I sporangiophores of Phycomyces blakesleeanus to determine whether the phototropic response had any structural correlate. Stimulated sporangiophores conserved the distinctive division into the four longitudinal zones described for state I, and showed no significant differences in the distribution of major organelles in the sides proximal and distal to the light source. On the other hand, apical vesicles were asymmetrically distributed, being present in lower numbers in the faster growing (distal) side of the sporangiophore. We suggest that this asymmetrical distribution reflects the differential utilization of vesicles necessary to sustain the corresponding growth rate of each side. Illumination therefore, must affect the rate of vesicle migration and utilization, more than their rate of synthesis.     

THE FUNCTION OF P700 AND CYTOCHROME f IN THE PHOTOSYNTHETIC REACTION CENTER OF SYSTEM 1 IN RED ALGAE

Abstract— Kinetics and quantum yields of light-induced oxidation of P700 and the f -type cytochrome were measured in marine red algae from absorbance changes in the region 420, 435 and 705 nm. The quantum yield for cytochrome oxidation in Iridaea splendens and Schizymenia pacifica was 0.5-0.65 in far-red light, at 20 and at 0C.
Oxidation rates of P700 measured when varying amounts of cytochrome were in the oxidized state indicated that a reaction center of system 1 in Iridaea contains 1 P700 and 4 cytochrome molecules. Oxidized P700 only accumulates when all 4 cytochromes are oxidized. The rate of photochemistry of system 1, measured as the sum of the rates of P700 and cytochrome oxidation, was independent of the oxidation level of cytochrome, but decreased with accumulation of oxidized P700. This decrease was less than proportional to the fraction of P700 that was in the oxidized state, which suggested transfer of excitation energy between reaction centers.
The quantum yield for cytochrome oxidation after dark periods of 1 min or more was only about 0.2. This effect was tentatively ascribed to a dark reduction of the cytochrome coupled to phosphorylation.     

LIGHT AND pH INDUCED CHANGES IN THE SURFACE PRESSURE-AREA ISOTHERMS OF BACTERIORHODOPSIN

Abstract— Pressure-area isotherms of monolayers of purple membrane fragments were measured at an air-water interface. The pH of the aqueous phase was varied from 2 to 10. Over the pH range 5 to 9 the area/molecule of bacteriorhodopsin was constant and illumination of the film had no effect on the isotherms.
At pH's more acid than 5 and more alkaline than 9, there were large decreases in area/molecule. Under these conditions of extreme pH the monolayer was very sensitive to light. Illumination resulted in irreversible increases in area/molecule.     

INDUCTION OF LEAF UNROLLING BY PHYTOCHROME and ACETYLCHOLINE IN ETIOLATED WHEAT SEEDLINGS

Abstract-Phytochrome regulates the unrolling of primary leaf sections from 8-day-old dark-grown wheat ( Triticum aeslivum L. cv. Arminda) seedlings. Red light (R)-stimulated unrolling of leaf sections pretreated in 1 m M ethylene-bis-(β-aminoethylether)- N,N,N',N' -tetraacetic acid (EGTA) if 1 m M CaCl₂ was added during a 30 min treatment period including and following irradiation. Nifedipine at 1 μ M (a Ca²+-channel antagonist) applied 10 min before R prevented the R stimulation of leaf unrolling. The Ca²+-channel agonist Bay K-8644 (1 μ M ) and acetylcholine (ACh, 1 mY M ) stimulated unrolling of leaf sections prewashed in EGTA in darkness, if 1 m M CaCl₂ was present in the medium during a 30 min treatment period. Acetylcholine also induced leaf unrolling in the absence of Ca²+ when 100 μ M NaCl was present in the medium. Apart from ACh, only carbamylcholine out of the choline derivatives tested was active in induction of leaf unrolling in the presence of 1 m M Ca²+. The ACh receptor antagonists, atropine (10 μ M ) AND D-tubocurarine (10 μ M ), nullified the ACh-induced Ca²+- and Na+-dependent leaf unrolling, respectively. Muscarine and nicotine, agonists of ACh, at 1 μ M stimulated leaf unrolling in the presence of Ca²+ and Na+, respectively. The ACh-induced Ca²+-dependent leaf unrolling was reduced by 1 μ M Nifedipine, 10 μ M Li+ and 10 μ M "calmodulin" inhibitor, trifluoperazine (TFP), whereas only TFP was active in the reduction of the Na+-dependent ACh-induced leaf unrolling response. It is proposed that leaf unrolling of dark-grown primary wheat leaves can be regulated by phytochrome and by activation of two different types of ACh receptors.     

STOICHIOMETRY OF THE REDOX CHANGES OF MANGANESE DURING THE PHOTOSYNTHETIC WATER OXIDATION CYCLE

Abstract— The UV absorbance change associated with the oxygen-evolution cycle is investigated as to its correlation with the successive redox (S-) states of the system. This change is probably due to a manganese oxidation within a multinuclear Mn-cluster. The stoichiometry of its formation and destruction during the S-cycle has been a matter of controversy: (0,1,0,-1) according to velthuys, B. R. (1981) in Photosynthesis II , (Edited by G. Akoyunoglou), pp. 75–85. Balaban International Science Services, Philadelphia, or (1, 1, 1, -3) according to Dekker, J. P., Van Gorkom, H. J., Wensink, J. and Ouwehand, L. (1984) Biochim. Biophys. Acta 767, 1–9. We show that the data obtained in flash-series experiments on dark-adapted material may be fitted as satisfactorily by both models. More discriminating tests were devised, varying parameters such as the double-hits probability or the initial distribution of the S-states. These experiments clearly indicate that no (or little) absorbance change occurs both upon S₀→S₁ and S₂→S₃ transitions. This suggests that the correct stoichiometry is (0,l,0,-1). The possibility of a non-integer stoichiometry may also be considered.     

NITROGEN FIXATION OF Azorhizobium IN ARTIFICIALLY INDUCED ROOT PARA-NODULES IN WHEAT

Nodule-like structures (para-nodules) can be induced in wheat roots by low concentrationsof 2,4-dichlorophenoxyacetic acid (2,4-D), a synthetic analogue of the plant growth hor-mone indole-acetic acid. Growth of nodulated wheat plants was not affected by 2,4-D treat-ment. Infection of these?para-nodules by adding oxygen-tolerant Azorhizobium caulinodans isolat-ed from stem nodules of the tropical legume Sesbania rostrata resulted in massive prolifera-tion of bacterial cells in the intercellular spaces as well as inside the para-nodular cells.Para-nodules colonized by Azorhizobium coulinodans not only reduced acetylene, but alsotransferred fixed nitrogen to the plant, contributing up to 16--23% of the nitrogen budgetof infected wheat.     

KINETICS OF PHOTOSYNTHETIC APPARATUS ADAPTATION IN Scenedesmus obliquus TO CHANGE IN IRRADIANCE AND LIGHT QUALITY

Abstract— Cells of the unicellular green alga Scenedesmus obliquus grown under high (20 W m^-2) or low (5 W m^-2) irradiancies of white light show all characteristics of sun or shade plants, respectively. When transferred to alternate light conditions, the cells adapt within 6 h. When cells grown under high irradiance of white light are transferred to red (683 nm) or blue (424 nm) light, they show characteristics similar to cells adapted to low or high irradiancies of white light, respectively. This adaptation to different wavelengths takes about 12 h. The underlying changes in the photosynthetic apparatus are discussed.     

THE FUNCTION OF PHYTOCHROME IN THE NATURAL ENVIRONMENT–V. SEASONAL CHANGES IN RADIANT ENERGY QUALITY IN WOODLANDS

Abstract. The spectral distribution of radiant energy on the floor of three typical English woodlands (birch, beech and oak) has been monitored throughout the whole growing season. The results are presented in terms of the changes in the ratio of the photon fluxes at 660 nm and 730 nm (τ) and in the photosynthetically active radiation (PAR). The results are discussed in relation to the hypothesis that the role of phytochrome is to detect changed light quality due to mutual shading and to direct development accordingly.     

含过渡金属离子的交联蒙托土交联柱中Keggin结构的作用

利用Keggin结构可以发生同晶取代的性质,合成了含过渡金属离子铬、镍的羟基铝交联蒙托土,并运用XRD、~(27)Al-NMR、UV-DRS、XPS、TPR等方法研究了Keggin结构的作用。结果表明,铬、镍都可以和铝生成具有Keggin骨架结构的羟基共聚体,并以此作柱子支撑着蒙托土的层间。铬的取代反应比镍容易发生。共聚法合成出的羟基镍铝交联蒙托土中镍存在两种状态;过量的金属离子对Keggin结构有较大地破坏;Keggin结构的存在增加了交联蒙托土的热稳定性。     

GENETIC VARIATIONS AND LINOLENIC ACID INDUCED CHANGES IN THE ORIENTATION PATTERN OF CHLOROPHYLL a IN THYLAKOID MEMBRANES

Abstract Orientation pattern of the Q_y absorption and emission dipoles of chlorophyll a were studied in wild type Scenedesmus obliquus and in mutants deficient in chlorophyll b and carotenoids. Fluorescence polarization ratio at –140°C and linear dichroism at 25°C were measured in whole cells and thylakoids aligned in polyacrylamide gel. Unlike normal thylakoids, mutants displayed fluorescence polarization ratios significantly lower than 1.0 and showed a negative LD signal around 672 nm, indicating the tendency of the Q_y dipoles to tilt out from the membrane plane. Such an orientation pattern can also be artificially induced by treating normal thylakoids with linolenic acid.     

ENERGY TRANSFER AND CYTOCHROME FUNCTION IN A NEW TYPE OF PHOTOSYNTHETIC BACTERIUM*

Abstract— The excitation spectrum for bacteriochlorophyll b fluorescence at 1027 mμ in Rhodopseudomonas sp. NHTC 133 indicates that the efficiency of energy transfer from caro-tenoid to bacteriochlorophyll b is between 27 and 28 %.
Light-induced absorbancy changes in anaerobic whole cells indicated the oxidation of three c -type cytochromes (C-550. 5, C-553, C-558) and one b -type cytochrome or cytochromoid C (C-560). At low light intensities C-553 is the main cytochrome oxidized, while at high light intensities mainly C-558 is oxidized in addition to C-553. The light responses of the heme proteins appear to be similar to those observed previously in purple and green photo-synthetic bacteria. No light-induced shifts in carotenoid absorption bands were detected.
In bacterial extracts C-553 and C-558 are bound to the chromatophores, while C-550. 5 is soluble.     

CHANGES IN FLUORESCENCE SPECTRA OF CHLOROPLASTS INDUCED BY A NATURALLY-OCCURRING FACTOR

Abstract— –Fluorescence emission changes (measured at – 196°C) of Ricinus chloroplasts incubated in isolation medium, and of chloroplasts from algae and higher plants incubated in Ricinus leaf extract, are described. Such incubation results in a transformation of the three-banded emission spectrum (F735, F698, F685) into a virtually one-banded spectrum, with maximum at 698 nm. That these changes are a consequence of the conversion (deaggregation) of the form of chlorophyll giving rise to F735 into a form contributing to fluorescence at 698 nm is suggested on the basis of room temperature absorption and low temperature fluorescence excitation studies, made concomitantly with the low temperature emission studies.     

THE APPLICATION OF ION EXCHANGERS IN THE PREPARTION OF WHEAT AGGLUTININ

In order to refine the products of wheat germ agglutinin (WGA) , several ion exchangers, such as D261,732, DEAE - cellulose -32 and CM - cellulose - 32, have been used to removed proteins and pigments with different colors, such as brown, red, yellow, green and black, in the extracts of wheat germ. The WGA obtained from this procedure has higher hemagglutination activity than that available from sigma Co. The minimum hemagglutination dose of the purified WGA for an equal volume of a 2% type A red blood cells is 4μg/ml. WGA is a mixture of isolectins with different isoelectric points, 5. 9, 6. 2 and 6. 8. Their molecular weight identified by SDS-polyacrylamide gel electrophoresis are 15 ,000 dalton , 18,000 dalton and 35,000 dalton, respectively.