Recherches Cytotaxonomiques et Cytogéographiques surMinuartia sect.Sabulina en Turquie (Caryophyllaceae)

25 populations from Turkey and one of Syria belonging to theSabulina section of the genusMinuartia have been karyologically examined. New chromosome numbers have been recorded forM. mesogitana andM. hybrida subsp.turcica, and a new variety was found in theM. hybrida complex. The origin of the taxa with n = 23 and n = 35 is discussed.

     

Climatic and anthropogenic effects on the sedimentation and geochemistry of Lakes Bourget,Annecy and Léman

During the last glaciation, the Rhone glacier extended as far as the region of Lyon and covered Lakes Bourget, Annecy and Léman. Glacial retreat successively freed Lakes Bourget and Annecy, it reached Geneva around 14 000 B.P. and the head of Lake Léman at about 12 000 B.P. Deposits situated between Nyon and the foot of the Jura provide a complete palynological zonation and serve as a type section for the lake core studies. A palynological horizon (about 1 800 A.D.) has been found in Lake Bourget and wood has been dated at 3 230 ± 65 B.P. (¹⁴C) in a core from Lake Léman. Three 6 m cores from each lake were sampled together with many 0.5 m cores from Léman. The short Lake Léman cores have been dated by ¹³⁷Cs and provide a precise indication of changes in the basin during recent decades. Holocene climatic variations are evident in the Léman cores and are reflected by concentrations of carbonate and organic carbon which increase at the end of the Alleröd and reach a maximum in the Atlantic Period (climatic optimum). Human settlement on the shores of Lake Annecy is shown by increases in heavy metals; increased sedimentation rates suggest settlement at the beginning of the Christian era. All the cores show increases in the organic matter and nutrients; from the turn of the century in the Léman, and later for the other lakes where eutrophication started only a few decades ago. NAI-P shows a very recent increase, around 1965 in the Leman. Heavy metals (Hg, Cd and Pb) show increases at about 30 years ago in Annecy, at about the turn of the century in Lake Léman and in the mid-19th century in Lake Bourget.

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Résumé Lors de la dernière glaciation, le glacier du Rhône a atteint la région de Lyon et recouvert les lacs du Bourget, d'Annecy et le Léman. Son retrait a successivement libéré les lacs du Bourget, d'Annecy, puis le Léman de leur carapace de glace. Aux environs de 14 000 ans B.P. son front se trouvait au voisinage de Genéve, puis vers 12 000 B.P. à l'embouchure du Rhône en amont du Léman.La chronostratigraphie des grandes carottes (6 m) prélevées dans les trois lacs a été établie par la palynologie, sur la base des zonations obtenues dans un profil complet provenant d'un marais situé entre Nyon et le pied du Jura. Elles ont pu être contrôlées par un marqueur palynologique dans le lac du Bourget (150 B.P.) et la datation au ¹⁴C d'un fragment de bois dans le Léman (3 230 ± 65 B.P.). Une série de carottes de grand diamètre provenant de ce dernier lac, datés par le ¹³⁷Cs, ont donné une image très précise du l'évolution du milieu durant les dernières décades. D'une facon générale, toutes les carottes montrent une augmentation des teneurs en matière organique, puis en nutrients, vers le fin du 19ème siècle pour le Léman et quelques dizaines d'années plus tard pour les lacs du Bourget et d'Annecy. Le début du l'etrophisation se situe beaucoup plus tard dans le Lémen avec l'accroissement des teneurs en phosphore, principalement de ses formes NAI-P et O-P, soit aux environs de 1965.

     

Climatic and anthropogenic effects on the sedimentation and geochemistry of Lakes Bourget,Annecy and Léman

During the last glaciation, the Rhone glacier extended as far as the region of Lyon and covered Lakes Bourget, Annecy and Léman. Glacial retreat successively freed Lakes Bourget and Annecy, it reached Geneva around 14 000 B.P. and the head of Lake Léman at about 12 000 B.P. Deposits situated between Nyon and the foot of the Jura provide a complete palynological zonation and serve as a type section for the lake core studies. A palynological horizon (about 1 800 A.D.) has been found in Lake Bourget and wood has been dated at 3 230 ± 65 B.P. (¹⁴C) in a core from Lake Léman. Three 6 m cores from each lake were sampled together with many 0.5 m cores from Léman. The short Lake Léman cores have been dated by¹³⁷Cs and provide a precise indication of changes in the basin during recent decades. Holocene climatic variations are evident in the Léman cores and are reflected by concentrations of carbonate and organic carbon which increase at the end of the Alleröd and reach a maximum in the Atlantic Period (climatic optimum). Human settlement on the shores of Lake Annecy is shown by increases in heavy metals; increased sedimentation rates suggest settlement at the beginning of the Christian era. All the cores show increases in the organic matter and nutrients; from the turn of the century in the Léman, and later for the other lakes where eutrophication started only a few decades ago. NAI-P shows a very recent increase, around 1965 in the Leman. Heavy metals (Hg, Cd and Pb) show increases at about 30 years ago in Annecy, at about the turn of the century in Lake Léman and in the mid-19th century in Lake Bourget.

     

Production of CO2 in the living mouse immediately after injection of 1- or 2-14C acetate.

Three groups of mice, normally fed, fasted and fed after a fasting period are injected intravenously with either 1- or 2-14C acetate. The respiratory 14CO2 as well as that of the liver, the adipose tissue and the carcass are collected after 3 min and the radioactivity measured. A determination is also made of the radioactivity of the tissue fatty acids and, for two groups of mice, of the circulating glucose. A calculation is suggested by which the number of revolutions performed by the acetate C in the Krebs cycle before it is transformed into CO2 can be deduced. The results suggest that the Krebs cycle is very open, that the acetate C found in the glucose has already broken away from the cycle after one revolution and that the C which appears in the form of CO2 has performed an average of only 2.8 to 3.6 revolutions. The results are evaluated as a function of the experimental conditions chosen.     

Rapid production of a biotin deficiency in mice]

This work describes a rapid method for the production of a biotin-deficiency in mice. Besides classical morphological symptoms, a decrease of activities of some biotin-dependent enzymes was also observed. The biotin-enzymes are not inhibited at the same extent in a same organ and the metabolic changes do not always follow the enzymatic modifications.     

Croisements expérimentaux entre «Races Chromosomiques» dans le genreErysimum

Artificial hybrids between dysploid chromosome races or microspecies ofErysimum sylvestre group are produced. From the meiotic behaviour it is inferred thatE. montosicolum (n = 14) is an autopolyploid ofE. australe (n = 7) and that the Italian race with n = 11 is probably derived from an unknown tetraploid.