PHOTOBIOLOGIE DU MESOCOTYLE D'AVOINE I- ACTION DES RADIATIONS ROUGE CLAIR ET ROUGE SOMBRE

Abstract— Red light (around 6,550 Å.) and far-red light (around 7,300 Å) have been administered to excised first internodes of etiolated oat seedlings, and their effects upon growth by elongation have been studied. It has been found that red light inhibits much more the elongation produced bv gibberellic acid (GA) than that produced by 3-indolylacetic acid (IAA). Far-red light acts synergistically with GA in promoting elongation, but not with IAA. The effect of far-red is localized in the node and in the first 4 mm below the node, at least when the seedlings are 63 hr old. The stimulatory effect of the far-red radiation is observed when seedlings are younger than 65 hr or older than 69 hr after sowing. Except for a gradual decrease with age, there is no such two-peaked pattern for the sensitivity to red light. Red light promotes the elongation of the node and of the 2 mm-zone of the first internodes immediately below it. It inhibits the elongation of the zone comprised between 2 and 10 mm below the node. Various types of experiments could not demonstrate a true reversal of the red effect by far-red light and vice-versa . They indicated rather an additive effect of the inhibitory and stimulatory properties characteristic of each type of radiation.     

PHOTOBIOLOGIE DU MÉSOCOTYLE D''AVOINE-III. DOUBLE EFFET DE LA LUMIÈRE BLEUE

Abstract— Using excise sections of oat first-internodes, a dual effect of blue light can be demonstrated on elongation when the sections are first irradiated in distilled H₂O, then incubated with gibberellic acid (GA). At low light energies (230 ergs/cm² per sec, for 2 min), a pretreatment with blue light enhances the GA effect above the elongation it can produce in the dark. At high energies (650 ergs/cm²/sec for 45 min), the same wavelengths cause an inhibition of the GA-induced elongation. An action spectrum for the two effects show a maximum near 435 mμ in both cases. Neither light effect is visible when indoyl-3-acetic acid is used instead of GA. Several physiological effects distinguish the two blue effects. The promotive effect is most marked in the young regions of the mesocotyl, whereas the maximum inhibitive effect is located in slightly older tissues. Time-course experiments showed that the promotive effect is partly due to an extension of the duration of elongation. The inhibitory effect is only temporary and vanishes about 30 hr after the beginning of the experiment. The promotive effect of blue light resembles the effect of far-red light, but the former can be observed with gibberellins A₂, A₄, A₅, A₆ and A₇ which are practically inactive after an irradiation with far-red light. The inhibitory effect of blue light is different from the red-light effect as shown by the time-course experiments.     

SEPARATION ET CARACTERISATION SPECTROSCOPIQUE DU MONOMERE ET DES POLYMERES DE LA C. PHYCOCYANINE.*

Abstract— Monomer, trimer and hexamer states of C. Phycocyanin chromophore protein have been isolated. Owing to a very slow approach to equilibrium mixing, it has been possible to estimate the number of each type of the two chromophores ‘s’; and ‘f’ present, using a fluoros-cence polorization method. It is found that there is one s chromophore and one f chromophore per protein monomer of molecular weight 30,000, a value in agreement with the monomer mol. wt. determined by Berns et al and by thermodynamic measurements in this laboratory. Absorption and fluorescence spectra of hexamer and monomer solutions have been compared. The hexamer solution shows greater fluorescence than the monomer solution, a phenomenon that may be attributable to a change in environment of chromophore following polymerization, with consequent change of fluorescence yield of each chromophore type and/or variation in energy transfer between them.     

PHOTOBIOLOGIE DU MÉSOCOTYLE D'AVOINE—II. STIMULATION DE L'ÉLONGATION PAR LA LUMIÈRE ROUGE-SOMBRE EN PRÉSENCE DE DIVERSES GIBBÉRELLINES

Abstract— Far-red light has the property of promoting the elongation of Avena mesocotyl sections in the presence of a gibberellin. Part of this effect is not reversible by red light (around 655 mμ ). The wavelengths which are most effective are those in the neignbourhood of 720 mμ , as revealed by the action spectrum. Amongst the 8 gibberellins tested, only A₁, A₃, and A₉, are capable of producing, after far-red irradiation, a greater elongation than the one they cause in the dark.     

CONTRIBUTION A L'ÉTUDE DU RÔLE DE LA LUMIÈRE DANS LA SEXUALISATION DU GAMÉTOPHYTE DE MARCHANTIA POLYMORPHA L.

Abstract— Gemmae of Marchantia polymorpha L. were grown in artificial light (16 hr, 4000 lx), aseptic conditions, at the Phytotron of Liège. It was shown that:
(1) Two distinct phases are obvious in growth and development of the gemmae:
(a) A juvenile phase with a minimum length of 15 days in any kind of light quality, on a mineral nutrient medium.
(b) An inductive phase , during which the inception of primordia occurs in incandescent light.
(2) When 1% sucrose is added to the mineral nutrient medium, the length of the juvenile phase is reduced to 5 days; however, sucrose has no action when it is provided in the dark.
It is assumed that the inductive incandescent light may promote a high energy reaction which is required for sexual induction.     

ACTION DE LA QUANTITÉ JOURNALIÈRE DE LUMIÈRE SUR LA FLORAISON, LE POIDS SEC ET LA TENEUR EN EAU DE QUELQUES PLANTES DE JOURS COURTS ET DE JOURS LONGS

Abstract— Experiments were carried on in the Liège Phytotron for two years to discover what reactions could be obtained when both short-day and long-day plants were placed in the same light energy per day (light intensity × daily light duration in various combinations) and receiving respectively 8 or 16 hr light per day. It was observed that both types of plants give parallel dry weight curves in both long-day and short-day, but this happens only during the vegetative state following germination.
Differences occur in those dry weight curves in short-day plants and also in long-day plants when cultivated under inductive photoperiodic light and induced to flower.
In these suitable light conditions, their dry weight increased compared with that of plants left in a non-inductive photoperiodic fight.
The evolution of tissue water content (stems, leaves, flowers), expressed as water % of the dry weight, is also interesting to observe in the same experimental environments. This evolution plays an important physiological part in flower formation, as has been shown before by R. Bouillenne.
Both types of plants cultivated in their respective non-inductive light point out a very simple curve of water content. First a rapid increase of water into the tissues during the first 10 days after germination; then from this maximum, the curve goes down regularly and slowly till a constant low level.
However, in inductive light exposure, water content percentage curves are really different for both types of species. Considering the same daily value of light energy given in each case, it is possible to conclude that the induction of flower does not depend on the daily light quantity but on something else which is connected with the photoperiodism.
These fluctuations of the water content will be investigated.     

OXAZOLIDONES ET DIOXOLONNES DU GERMANIUM (IV) ET (II) DU PHOSPHORE (III), DE L'ARSENIC (III) ET DU SOUFRE

Abstract

Diffèrents modes de synthèse d'oxazolidones 1.2.4-7 et de dioxolonnes 8-11 germaniées sont décrites.

La stabilité thermique de germadioxolonnes a été étudiée. La décomposition procède d'un méchanisme du type (2 + 2 + 1), avec ouverture du cycle et formation de germylène.

La réactivité chimique des oxazolidones et dioxolonnes germaniées a été étudité. Des réactions d'échange avec des dérives organominéraux dichlorés conduit facilement et avec de bons rendements aux derives isologues, phosphorés(III). arseniés(III), soufrés. ou germaniés(IV). La réaction d'échange entre une dioxolonne germaniée et le dichlorogermylène nous a permis d'obtenir un nouveau germylène fonctionnel cyclique stable 20 qui a été caractérisé par spectrographie (RMN ¹H. masse).

Different synthetic ways for germaoxazolidones 1.2.4-7 or dioxolonnes 8-11 have been described.

The thermal stability of germadioxolonnes has been studied. Decomposition occurs by a [2 + 2 + 1] ring opening with formation of germylene.

The chemical reactivity of germaoxazolidones or dioxolonnes has been studied. Exchange reactions with dihalogenated covalent compounds occur readily lcading to phosphorus(III). arsenic(III). sulphur or germanium(IV) analogs.

From dichlorogermylene, new stable fonctionnal cyclic germylene 20 is obtained and characterized.     

ACTION DE LA TEMPERATURE SUR LA DUREE DE VIE DE FLUORESCENCE ET LE RENDEMENT DE FLUORESCENCE DE LA C-PHYCOCYANINE EN SOLUTION

Abstract— The influence of temperature on the fluorescence yield and lifetime (measured by a phase fluorimeter) of C-hycocyanin in various forms of polymerization in solution, was studied over the temperature range 0–75°C. The temperature dependence of φ and φ below 50°C may be ascribed to an effect on internal conversion, with activation energy of 0.45. eV. Above 50°C, a large enhancement of is observed which may be due to the appearance of direct fluorescence from the sensitizer chromophores, the transfer efficiency between the two different chromo-phores present in each monomer being decreased by protein denaturation. At room temperature, there is almost no difference between the lifetimes of the different polymers, whereas large differences between their fluorescence yields are observed. Therefore, a static quenching of the fluorescence of the chromophores by the solvent molecules may occur.     

ETUDE DE LA FRAGMENTATION DE N-ARYL ET DE N-ALKYL AMINOCETONES EN SPECTROMETRIE DE MASSE

A Comparison of the chemical ionisation and elctron-impact mass spectra of alkyl and aryl aminoketones has bee carried out. This has revealed the particular stabilization of the N-aryl grops in all cases.     

SYNTHESE DE L'HYDROXYAPATITE PURE A PARTIR DE L'ACIDE PHOSPHORIQUE ET DU CARBONATE DE CALCIUM

L'hydroxyapatite de formule Ca₁₀(PO₄)₆(OH)₂ a été élaborée à 100°C et à pH 8 par précipitation à partir d'une solution de calcium, obtenue à partir du carbonate de calcium, et d'une solution de phosphate obtenue à partir d'acide phosphorique. Le procédé consiste à additionner les réactifs avec un rapport atomique Ca/P égal à 1,667. La caractérisation et l'analyse chimique de la poudre synthétisée ont été effectuées par diffraction des rayons X (XRD) des poudres, spectroscopie infrarouge à transformée de Fourier (FTIR), BET, MEB, colorimétrie et par absorption atomique.

The hydroxyapatite of formula Ca₁₀(PO₄)₆(OH) ₂ was formed at 100°C and pH 8 by precipitation from a calcium solution obtained from calcium carbonate and a phosphate solution obtained from phosphoric acid. The process consists of adding reagents with an atomic ratio Ca/P equal to 1,667. The characterization and the chemical analysis of the synthetic powder were made by X-ray diffraction (XRD) of powders, Fourier Transform Infrared Spectroscopy (FTIR), BET, MEB, colorimetry, and atomic absorption. Mots clés: Hydroxyapatite; IR; précipitation; procédé; RX; synthèse     

COMPORTEMENT COMPARE DE L'EPICHLORHYDRINE,DE L'EPIBROMHYDRINE ET DE LEURS HOMOLOGUES VIS A VIS DU METHYLENETRIPHENYLPHOSPHORANE

Abstract

Condensation of methylenetriphenylphosphorane with epihalohydrines (X = Cl or Br) leads to 2,2-dihydro-2,2,2,-triphenyl-3,4-methano-1,2-oxaphospholane. The first step of this reaction depends on the nature of the halogene: a) attack on the epoxide group with X = Cl; b) attack on the halogenated function when X = Br. With 1-halogeno 2,3-epoxy butanes the reaction occurs according to b) and gives 2,2-dihydro-2,2,2-triphenyl-3,4-methano-5-methyl-1,2-oxaphospholane.     

ETUDE PAR FLUORESCENCE DE BASES DE SCHIFF DU PYRIDOXAL, COMPARAISON AVEC LA L ASPARTATE-AMINOTRANSFERASE

Abstract— –Absorption and emission spectra of Schiff bases of pyridoxal-HCI or pyridoxal-5-phosphate with L-valine, n -butylamine or N-α-acetyl-L-lysine-N-methylamide have been studied as a function of pH. We can write the complete ionization diagram and equilibria. The results of Martell[6] are confirmed: the forms analogous to the coenzyme in aspartate aminotransferase, which absorb at 410 nm and 360 nm (or 340 nm for the Schiff base with n-butyl-amine) have the phenol OH ionized; the imine nitrogen is protonated for species absorbing at 410nm (in the enzyme: inactive form and complex with aminoacid) and unprotonated for species absorbing at 360 nm (in the enzyme, active form). Their fluorescence wavelengths are respectively 500 nm and 430 nm. Protonation of the pyridine nitrogen of these forms does not shift the absorption band; the fluorescence intensity is 20-fold greater for the N-protonated forms.
The real pK of the imine nitrogen is 8.5 ±0.8 for species with pyridine N-protonated or 10.4 for the non-protonated forms. The observed pK 6.3 in the enzyme can be explained if the imine nitrogen is hydrogen bonded to an amino-acid side chain of the protein: lysine, tyrosine, serine, sulfhydryl.
The quantum yield of the coenzyme fluorescence in the enzyme has been compared to that of the analogous Schiff base (absorbing at the same wavelength). According to the results, we cannot deduce whether the pyridine nitrogen is protonated in pyridoxal form of the enzyme.
If it is protonated, as in the pyridoxamine form, the coenzyme environment is not the same in the two forms. If the pyridine nitrogen is unprotonated in the pyridoxal form and protonated in the pyridoxamine form, the environment of the coenzyme is the same in these two forms of the enzyme.     

CINETIQUE DES ECHANGES D'OXYGENE ET DE LA FLUORESCENCE DES CHLOROPLASTES ISOLES

Abstract Oxygen evolution and fluorescence have been studied with isolated chloroplasts illuminated, in the absence of Hill reagents, by flashes or continuous light. As in whole cells, at least two substances are involved in the primary process leading to the oxygen evolution. The first, called E, probably is the photochemical “complex” of System II. After a long period of darkness, E is not active. It is activated in two steps. Step one is a photochemical reaction, induced by a quantum of light absorbed by pigment-system II, which results in the production of E in a reduced state. Step two is a dark oxidation of the reduced E by the second substance, A. The oxidized E can then enter the normal photochemical cycle of system II. Reduced E might alternatively be oxidized by oxygen, this reaction being responsible for a very rapid and brief light-induced oxygen uptake. Substance A is measured by the oxygen burst and is present in the chloroplasts at the approximate ratio of 1 molecule for 70 molecules of total chlorophyll while E is at the ratio of about 1/2800. This gives a E over A value of 1/35 which is much smaller than the one found in whoe cells (ca. 1/10). This independent behavior of E and A suggests that chloroplast extraction destroys some photochemical centers without having a direct impact on A, which might diffuse from one center to another. Besides the brief light-induced oxygen uptake above mentioned, there is another one which is related to System I functioning. The kinetics of the oxygen evolution and of the fluorescence have been compared. During the activation process of the oxygen evolving ability, rate of oxygen evolution and fluorescence yield increase in a parallel way. After the maximum velocity of the oxygen burst is reached (i.e. after activation), the fluorescence yield keeps growing up until the steady-state is attained (with an intermediary plateau), whereas the rate of oxygen emission slows down. The time-course curves of fluorescence obtained with inactivated or activated chloroplasts are essentially different in that the initial yield is higher in the latter case.     

LA PHOTOOXYDATION DU GROUPE PEPTIDE—II. PEPTIDES ET POLYAMINOACIDES A L‘ÉTAT SOLIDE*

Abstract— The determination of glyoxylic and pyruvic acids in oligo-and poly-, glycine and alanine shows that the peptide group is photooxydized, probably with the radical -NH-CR-CO- as an intermediate. The characterisation of pyruvic acid in glutathione and oxydized glutathione confirms the photolysis of the C-S bond in combined cysteine and cystine. Finally, a comparison of the photoreactivity of peptides of the types aliphatic amino acid-aromatic amino acid and aromatic amino acid-aliphatic amino acid allows us to propose a selective mechanism for the transfer of excitation energy from the phenyl group to the preceding amino acid residue in the polypeptide chain.     

AGREGATION DES CHLOROPHYLLES IN VITRO-II. PHOTODECOLORATION DE LA CHLOROPHYLLE a ADSORBEE SUR DES PARTICULES DE LIPOPROTEINES EXTRAITES DU LAIT

Abstract— Chlorophyll a (chl a ) adsorbed on milk proteins or lipoproteins has absorption maxima at 437 ± 1 nm and 671 ± 1 nm, whatever its concentration. A 750-nm-absorbing form appears when (chl/proteins) > 2 × 10^-2 mg chl/mg proteins, in the case of lipoproteins; or 4.5 × 10^-3 mg chl/mg proteins, in the case of proteins. In both cases, the apparent molar extinction coefficient at 671 nm is the same (3 × 10⁴ liter mole^-1 cm^-1) at the highest (chl/proteins) ratio for which no 750 nm absorbancy appears. It is shown that adsorbed chl a undergoes irreversible (in the present conditions) photo-oxidation by light in the presence of oxygen. The reaction is second order, with similar rate constants for chl a adsorbed to proteins or to lipoproteins.     

ACTION DE LA LUMIÈRE SUR LA CROISSANCE DES TIGES PRINCIPALES DE L'ASPARAGUS MEDEOLOIDES

Abstract— Studies of the influence of light upon the growth of Asparagus medeoloides main stems show that the stem-length and the time-growth increase when the intensity of illumination decreases. There is no direct proportionality between growth and illumination intensity; a maximum is found at 660 lx.