C. Bulard

Bound and Free Abscisic Acid Levels in Dormant and After-ripened Embryos of Pyrus malus L. cv. Golden delicious

Summary The endogenous levels of both cis and trans isomers of free and bound ABA, were studied in dormant and after-ripened embryos of Pyrus malus L. cv. Golden delicious. Wheat cole-optile straight-growth test and gas-liquid chromatography (GLC) were used as quantitative methods. The level of free ABA was very high in dormant embryos, mainly in cotyledons, but turned very low after three months of stratification. Bound ABA increased considerably and became dominant in after-ripened embryos. Bound trans-ABA was found only in cotyledons of after-ripened embryos. The relation between free and bound ABA levels of apple embryos and their capacity to germinate is discussed.

Relative Levels of some Bound and Free Gibberellins in Dormant and After-ripened Embryos of Pyrus malus cv. Golden delicious

Summary Relative amounts of free and bound forms of several gibberellins (GA 3 GA 4 , GA 7 , GA 9 ) were determined in dormant and in after-ripened embryos of Pyrus malus L. cv. Golden delicious. We used a modified lettuce hypocotyl test applied after two thin-layer chromatographies. The latter allow a good separation of the different gibberellins studied from indol-acetic acid and abscisic acid. In order to avoid imbibition of the embryos before extraction, we submitted them to an after-ripening treatment inside the fruits. We showed that small quantities of free and bound gibberellins are present in the dormant embryos, mainly located in the cotyledons. In the embryonic axes of the after-ripened embryos, we found significant quantities of free GA 9 , and a very high level of bound GA 4 , whereas cotyledons contained small quantities only of the free and bound gibberellins tested. The significance of the large quantity of bound GA 4 , its possible origin and mobilization are discussed.

Changes in free and bound gibberellin levels in embryos of Pyrus malus cv. Golden delicious during a chilling treatment applied to the seeds

Summary The endogenous levels of free and bound forms of several gibberellins (GA 4 , GA 7 , GA 9 ) were studied in dormant as well as in partially or completely after-ripened embryos of Pyrus malus L. cv. Golden delicious, the seeds being submitted to a 4 °C chilling treatment for 1, 2 or 3 months. The GA s tested were isolated using thin-layer chromatographies which allowed the separation from ABA and IAA. Quantitative estimations were made using a lettuce hypocotyl test for GA 7 and GA 9 and an original amaranthin biossay for GA 4 . Very small quantities of GA S were found in dormant embryos under bound and free forms. Under the influence of chilling treatment, the content of GA 7 and GA 9 showed but slight modifications whereas free and bound forms of GA 4 underwent remarkable changes. In the cotyledons we found after 1 month after-npening treatment, a high GA 4 content essentially under the free form; after 2 or 3 months a similar level was detected under the bound form, the free form having disappeared. In the embryonic axes, free GA 4 was found in large amounts only after 2 months. Almost no bound form appeared whatever the length of the chilling treatment. The discussion is directed to the possible relation between the water content and GA 4 localization during the after-ripening treatment.

Metabolism of [2-14C]abscisic acid in dormant and Afterripened Apple Embryos

Summary Dormant and after-ripened embryos of Pyrus malus L. var. Golden delicious were incubated with (±) [2- 14 C]abscisic acid at 10 -5 M (947 MBq mmol -1 ) for various periods (2, 6, 9,12 days) at 24 °C in darkness. The embryos were extracted in 80 % ethanol. Two acidic diethyl-ether phases which contained the free acids and the acids released after mild alkaline hydrolysis, respectively, were analysed as well as the radioactivity which remained in the final aqueous phase. The results obtained indicated that ABA metabolism was very active in both cases since, despite continuing absorption, the percentage of the radioactivity represented by abscisic acid decrease as a function of time. Greater amounts of abscisic acid remained in after-ripened embryos than in dormant embryos. The surplus of abscisic acid metabolized was found almost exclusively in the form of a-D-glucopyranoside abscisate while distribution of the radioactivity corresponding to other metabolites was not modified. There is, therefore, a tendency in dormant embryos towards the formation of β-D-glucopyranoside abscisate, a substance the role of which as a potential source of ABA has already been demonstrated in this material.

Irradiations à faible énergie et biosynthèse d'amarantine chez des plantules d'Amarantus tricolor L. var. bicolor ruber Hort.

SummaryA grating monochromator has been used to study the effect of narrow wave-bands (5 nm) at a low energy level between 420 and 800 nm on the biosynthesis of amaranthin in Amarantus tricolor L. var. bicolor ruber Hort. seedlings. Besides a sharp peak in the red with a maximum at 660 nm, a narrow zone of activity in the blue has been detected (max. 440 nm).When seedlings cultivated on different substrates were sequentially exposed either to red (660 nm) and far red or to blue (440 nm) and far red, the second treatment, i.e. far red (730 or 735 nm), annihilated the effect of the first one, without having any influence on the chemical inductive treatments (kinetin or dihydroxy-3,4-phenylalanine).A grating monochromator has been used to study the effect of narrow wave-bands (5 nm) at a low energy level between 420 and 800 nm on the biosynthesis of amaranthin in Amarantus tricolor L. var. bicolor ruber Hort. seedlings. Besides a sharp peak in the red with a maximum at 660 nm, a narrow zone of activity in the blue has been detected (max. 440 nm).When seedlings cultivated on different substrates were sequentially exposed either to red (660 nm) and far red or to blue (440 nm) and far red, the second treatment, i.e. far red (730 or 735 nm), annihilated the effect of the first one, without having any influence on the chemical inductive treatments (kinetin or dihydroxy-3,4-phenylalanine).

Uptake of [2-14C]abscisic acid and distribution of 14C in apple embryos

Pyrus malus L. var. Golden delicious embryos were incubated with (±)-[2-14C]abscisic acid (ABA) (10-5 M, 355 kBq μmol-1). After incubations of various durations, the radioactivity was measured in whole embryos, cotyledons, and embryonic axes.With either 48-h or 16-d incubation periods, the uptake of [14C]ABA depended upon the mode of culture used. The lowest values corresponded to the absorption by the embryonic axis, the highest to the absorption by the distal parts of the two cotyledons. The cotyledons accumulated the main part of the radioactivity under all conditions. Dormant and almost completely after-ripened embryos cultivated for 4 d showed no significant differences in the radioactivity uptake for identical modes of culture. There was a linear relationship between exogenous ABA concentrations (0.5 to 3.10-5 M) and ABA uptake for embryos cultivated for 4 d with the distal parts of the cotyledons immersed in the medium.

Séparation et Identification des Bétalaines Synthétisées par les Tissus de Tige de Myrtillocactus geometrizans Cultivés «in vitro»

Summary Sephadex gel column chromatography enabled us to separate betalains present in stem tissue cultures as well as in fruits of Myrtillocactus geometrizans. The identification of the isolated fractions was attempted by means of paper chromatography, electrophoresis, spectrum analysis and Sephadex gel chromatography. Three pigments — one betaxanthin and two betacyanins -, have been identified in both materials. Indicaxanthin and betanin were characterized with relative certainty. Another betaxanhin was tentatively identified as phyllocactin.

Acide abscissique et germination des akènes de Lactuca sativa L.cv. Attraktion à l'obscurité à différentes températures

Resume Le comportement germinatif des akenes de Lactuca sativa L. cv. “Attraktion” sur eaudistillee et a lobscurite depend de la temperature. Pour des experiences dune duree de 64 heures le pourcentage de germination atteint son maximum a 23 ou 24 °C, tandis quil diminue progressivement aux plus hautes temperatures (26, 28 et 29 °C). Aux cinq temperatures experimentees, facide abscissique utilise de 0,1 a 16 μM inhibe lagermination. Pour une concentration donnee son action augmente avec lelevation de la temperature. Ceci traduit une synergie entre faction de la temperature et celle de lacide abscissique.

Comportement en culture in vitro des tissus de tige de Myrtillocactus geometrizans (Mart.) Cons. (T.) et biosynthèse de bétalaïnes

ResumeNous avons essaye dobtenir des cultures de tissus a partir de fragments de tiges de plantules de Myrtillocactus geometrizans (Cactacee). Selon la nature des regulateurs de croissance ajoutes au milieu de base (IAA et kinetine ou 2–4 D et lait de coco) les explantats primaires produisent des racines et des bourgeons ou evoluent en cals. La croissance de ces cals a pu etre maintenue au cou des quarante-cinq transferts sur le milieu de LINSMAIER et SKOOG enrichi en IAA et kinetine. Les betalaines apparaissent dans les cals apres quatre semaines de culture. La quantite de pigment augmente en fin de culture. La tyrosine et le glucose ne favorisent pas la synthese de ces pigments.

Irradiations faible nergie et biosynthse d'amarantine chez des plantules d'Amarantus tricolor L. var. bicolor ruber Hort.@@@Low energy photocontrol of amaranthin formation in seedlings of Amarantus tricolor L. var. bicolor ruber Hort.

SummaryA grating monochromator has been used to study the effect of narrow wave-bands (5 nm) at a low energy level between 420 and 800 nm on the biosynthesis of amaranthin in Amarantus tricolor L. var. bicolor ruber Hort. seedlings. Besides a sharp peak in the red with a maximum at 660 nm, a narrow zone of activity in the blue has been detected (max. 440 nm).When seedlings cultivated on different substrates were sequentially exposed either to red (660 nm) and far red or to blue (440 nm) and far red, the second treatment, i.e. far red (730 or 735 nm), annihilated the effect of the first one, without having any influence on the chemical inductive treatments (kinetin or dihydroxy-3,4-phenylalanine).A grating monochromator has been used to study the effect of narrow wave-bands (5 nm) at a low energy level between 420 and 800 nm on the biosynthesis of amaranthin in Amarantus tricolor L. var. bicolor ruber Hort. seedlings. Besides a sharp peak in the red with a maximum at 660 nm, a narrow zone of activity in the blue has been detected (max. 440 nm).When seedlings cultivated on different substrates were sequentially exposed either to red (660 nm) and far red or to blue (440 nm) and far red, the second treatment, i.e. far red (730 or 735 nm), annihilated the effect of the first one, without having any influence on the chemical inductive treatments (kinetin or dihydroxy-3,4-phenylalanine).