Variation du taux d'acide abscissique chez deux variétés de poiriers, la Passe-Crassane et la Doyenne du Comice, en fonction de l'induction de la parthénocarpie par l'acide gibbérellique

The content of abscisic acid in the developing fruits of two cultivars of pear (Pyrus communis L.) was determined by UV spectrophotometry and by a colorimetric method based on the possibility of the lactone corresponding to abscisic acid to give a purple colour when sodium hydroxide is added. The young fruits were harvested either from trees treated with gibberellic acid (GA₃), for the purpose of inducing parthenocarpy, or from untreated trees. High levels of abscisic acid were associated with abortion and abscission of young fruits (June drop). There was little difference between fruits of GA₃-treated and untreated trees of the cultivar Passe-Crassane. In the other cultivar, ‘Doyenne du Comice’, the level of abscisic acid in the fruits of GA₃-treated trees was about twice as high as in control fruits and seemed to be directly related to the number of fruits per tree.     

Exemples de tératologie chez les Chitinozoaires du Pridoli de Libye et implications sur la signification biologique du groupe

Jaglin, J.-C. & Paris, F. 1992 04 IS: Exemples de tératologie chez les Chitinozoaires du Pridoli de Libye et implications sur la signification biologique du groupe. [Teratologic cases among Pridolian chitinozoans from Libya and implications on the biological interpretation of the group.] Lethaia , Vol. 25, pp. 151–164. Oslo. ISSN 0024–1164.
Fairly numerous chitinozoans displaying morphological anomalies are recorded in Late Silurian subsurface material from Western Libya. The individuals described and illustrated in our paper range exclusively in a short interval at the top of the investigated sequence. These abnormal vesicles are interpreted as teratologic cases related lo an event of unknown origin. From our conclusions, the hypothesis of vegetative reproduction stages stated by previous authors seems unlikely. Therefore we still interpret the chitinozoan vesicles as eggs (or to a lesser extent as spores) of marine organisms. * Libya, Chitinozoans, Silurian, teratology, chitinozoan affinities .     

La glutamine synthètase du Suaeda maritima. Action in vivo et in vitro du NaCl

The glutamine synthetase of Suaeda maritima. In vivo and in vitro action of NaCl Glutamine synthetase (GS; EC 6.3.1.2) was isolated and characterized from roots and aerial parts of the halophyte Suaeda maritima (L.) Dum. var. macrocarpa Moq. Km values of GS were identical in both types of organ and unchanged by the salinity in the medium. Addition of NaCl in the culturing solution increased the specific activity of the enzyme especially in the aerial parts, where GS is more abundant. This increase was all the more pronounced if the plant-salt contact period was extended (between 21 and 45 days). In vitro the addition of 0 to 500 m M of salt did not affect the activity of GS at satured substrate concentrations. At low glutamate concentrations in combination with 300 m M NaCl or more, a slight competitive inhibition was observed, never over 18%. – The remarkable insensibility of GS to salinity in vitro and the stimulating effect of NaCl in vivo on the synthesis of the leaf enzyme indicates that GS plays a fundamental part in the assimilation of NH4⁺ in the halophyte Suaeda maritima var. macrocarpa.     

Caractérisation de la glutamate déshydrogénase chez un halophyte obligatoire: le Suaeda maritima var. macrocarpa

Characterization of the glutamate dehydrogenase from an obligate halophyte: Suaeda maritima var. macrocarpa The glutamate dehydrogenase (GDH), E.C. 1.4.1.3, of the obligate halophyte Suaeda maritima (L.) Dum. var. macrocarpa Moq. has been studied. NaCl increase in the culturing solution (0 to 23 g NaCl/litre) lowers the specific activity but does not affect the kinetic characteristics of the enzyme collected after purification on G-25 Sephadex gel. In optimal conditions, GDH is activated by the addition of 25 mM NaCl in the incubation medium and inhibited with concentrations over 100 mM. The inhibitory activity of the salt induces both a modification of the affinity of the enzyme for substrate (competitive inhibition for ketoglutarate) and a modification of the catalytic potency (non-competitive inhibition with NADH and ammonium ion). It is suggested that NaCl has a depressing influence on GDH synthesis. There is a fundamental difference between its short time action (in vitro) versus its continuous effect in the culturing solution.     

Action de quelques phytohormones sur la respiration et ľabsorption du phosphate par des disques de tubercules de pomme de terre en survie

Action of some phytohormones on the respiration and on the absorption of phosphate by aging potato tuber discs. Discs of potato tuber incubated in aerated medium show an increase of the rates of respiration and phosphate absorption with aging time; the rates increase by two and nine respectively during the time period between 5 and 24 h of aging. Adenine or some N-6 substituted adenines [benzylaminopurine (BAP), furfurylaminopurine (FAP), methylaminopurine (MAP)], which present variable degrees of cytokinin activity, partially inhibit the increase of the rate of phosphate absorption and, to a lesser extent, the increase of the rate of respiration. Also abscisic acid (ABA), indole 3-acetic acid (IAA), and gibberellic acid (GA₃) produce inhibition of the increase of the rate of phosphate absorption with varied effects on the respiration. With regard to phosphate uptake, the effects of ABA, 1AA and GA₃ were additive to those of BAP. The effects on respiration were different from the effects on phosphate uptake, so that there is no direct relationship between inhibition of respiration and inhibition of phosphate uptake.     

La structure et I'innervation du diaphragme de la gaine tentaculaire chez deux Bryozoaires Malacostéges

Morphological and ultrastructural observations in Electra pilosu (L.) and Membranipora membranacea (L.) show that the diaphragm which closes the tentacular atrium is formed by the juxtaposition of folds of the tentacle sheath around its apical sphincter and another row of folds of the vestibulum. Double desmosomes bind the epithelium and cuticle at the base of vestibular folds to the collagen layer of the sheath. The continuity of parietal and polypidian cellular layers during the morphogenesis of the aperture is discussed. Several cellular types are differentiated in the microvillous epithelium of the sheath at the edge of the atrial orifice. The sphincter is innervated by twin motor branches of the mixed peripheral nerves. An efferent cluster of axonal fibres arises from bipolar neurons which are vitally stained by methylene blue within every vestibular lobe, with a slender dendrite reaching to the cuticle. The ramified dendritic ending encloses the kinetosomes and aborted root of a vestigial cilium. Interdigitation of the dendritic ramifications and marginal vesicles of adjacent epithelial cells which also contain a single reduced cilium is observed, although no particular junction implying a functional couple was found. Vestibular folds around the atrial orifice are interpreted as sensory papillae with either a mechano- or chemoreceptive function.     

Effets du GA3 et de la BAP sur la respiration,l’absorption et le métabolisme du phosphate chez des disques foliaires dePelargonium zonale après survie

Respiration rate of foliarPelargonium discs was insensitive to ageing. The addition of BAP or GA₃ to the ageing medium did not produce any effect. The presence of GA₃ or BAP in the ageing medium induced an increase (27 %) or a decrease (45 %) of the phosphate uptake. The analysis of phosphorylated compound labelling showed that these two hormones decreased³²P incorporation in the non-acid soluble fraction and increased³²P incorporation in the acid soluble organic fraction. GA₃ and BAP had little effect on the distribution of radioactivity between the different acid soluble compounds, but they increased the ATP level. These results suggest that both GA₃ and BAP increase the basal metabolism, but they seem to act differently on the development of the uptake mechanism during ageing.     

Figurations de l’amas stellaire des Pléiades sur deux roches gravées de la région du Mont Bego Z IX. GII. R 4 et Z IX. GIII. R 6

Two engraved rocks are situated 140 m from each other at an altitude of about 2250 m. One of them is called “female dancer”, and the other, “the Pleiads”, and both show a group of seven small pitted areas, of which one is smaller than the others and ‘ identified as the “Pleiads stellar cluster”, often depicted or mentioned during Antiquity and also throughout various historical periods.On each of these rocks, a large halberd, whose handle is oriented east-west, was traced along a natural fissure in the rock and engraved in the center of the composition. The “Pleiads stellar cluster” is represented on each of the two rocks beside the halberd : although situated to the west above the halberd blade on the “female dancer” rock, it is placed to the south and to the left of the halberd handle on “the Pleiads” rock. This difference may mark two distinct calendar data.The position of the different figures in the compositions illustrated on these two rocks, in particular inversions in the representation of some of them may indicate two distinct periods of the agricultural yearly cycle: on the rock called “female dancer”, the “heliacal raise” at summer's end, marking the beginning of the harvest and, on the rock called “the Pleiads”, the “heliacal setting”, just before winter, after the end of the harvest, when the rains soaks the ground and it is time to plow.     

Action de la proline exogène sur l'activité de la voie du glycolate chez Nicotiana tabacum cv. Xanthi n.c.

The effect of exogenous proline on the activity of the glycolate pathway in Nicotiana tabacum cv. Xanthi n.c. An exogenous proline supply in the light provokes an increase in free glycine concentration in apical tissues or in leaf disks of vegetative Nicotiana tabacum L. cv. Xanthi n.c. This does not occur in the equivalent tissues of tobacco plants after floral induction, these being naturally rich in proline. In vegetative tobacco, we have tried to determine this specific action of exogenous proline. With ¹⁴C glycine, ¹⁴CO₂ experiments (Pulse-chase) and glycine decarboxylase activity determinations, we observed that glycine-serine transformation was inhibited by proline supply. Presently it is important to determine if endogenous proline acts on the same reaction.     

Effet de l'osmolarité et de la composition du milieu sur la callogénèse,la caulogénèse et la rhizogénèse de fragments d'hypocotyles deBrassica oleracea L. var.botrytis

Callus formation by fragments of cauliflower hypocotyls was favoured by raising culture medium osmolarity above ?0.38 MPa. Increase in sucrose concentration while diminishing macronutrients inhibited callus initiation and growth. Root formation by the same material required a low medium osmolarity (?0.19 MPa). Reducing sucrose concentration in the classical Murashige and Skoog rooting culture medium favoured root formation. Adventitious bud formation was also depending upon medium osmolarity besides the need for a cytokinin. Reducing too much the osmotic potential of the medium had an unfavourable effect on bud neoformation. The importance of sucrose in all these processes is pointed out.