M. Coumans

Organogenesis in habituated sugarbeet callus: auxin content and protectors, peroxidase pattern and inhibitors

Summary A comparison of the soluble, membrane- and cell wall-bound peroxidases of an organogenetic and a nonorganogenetic habituated sugarbeet callus showed that organogenetic tissues contained a higher level of peroxidase activity and a larger number of peroxidase isoenzymes. Partially (through G-100 Sephadex) purified peroxidases of organogenetic callus likewise exhibited higher auxin-oxidase activities. Organogenetic tissues also were found to contain higher levels of peroxidase inhibitors and auxin protectors (auxin-oxidase inhibitors). A GC-MS analysis of IAA indicated a lower level of the hormone in the organogenetic callus. This presumably leads to an auxin-cytokinin ratio compatible with the induction of shoot formation.

Stabilized Dormancy in Sugarbeet Fruits. I. Seed Coats as a Physicochemical Barrier to Oxygen

Naked seeds removed from dormant sugarbeet fruits gave 93% germination on moistened filter paper in petri dishes while entire fruits gave only 25% germination at any period of the year. Water retention by cotton wool underneath the filter paper diminished the film of water covering the fruits, resulting in better germination. Removing the operculum and placing the fruits with the basal pore downward also yielded better germination. During imbibition gas adsorbed by the fruit wall was rapidly released, after which gas reabsorption occurred. The operculum accounted for 62% of the gas absorption. The sugarbeet fruit wall was compared with a solution of phenolics which, by absorbing oxygen, acted as a physicochemical oxygen barrier for the embryo.

Vegetative multiplication of sugarbeet through in vitro culture of inflorescence pieces

In vitro vegetative multiplication of sugarbeet was obtained by culturing of inflorescence explants. Subapical segments or 5-mm-long tips from nine varieties developed axillary shoots (up to 50 per tip) on a medium containing indolebutyric acid (IBA) and benzylaminopurine (BAP). Zeatin was ineffective as cytokinin. Gibberellic acid (GA3) enhanced the process. Such vegetative shoots were subsequently isolated and were each allowed to develop up to 20 supplementary axillary shoots on a multiplication medium containing IBA, BAP, and naphthaleneacetic acid (NAA). Rooting of shoots was obtained in the absence of growth regulators and plants were established.

High-performance gas chromatography of 1,4-naphthoquinones fromDroseraceae

SummaryThe analysis of natural 1,4-naphthoquinones from different species ofDroseraceae was performed by means of a direct GC method without derivatization. A simple and rapid extraction by toluene was used which did not need further purification. The sensitivity of the method allowed naphthoquinone estimation in one organ (leaf or root) only.The identity of plumbagin and 7-methyljuglone was confirmed by mass spectrometry.

Induction de bourgeons adventifs sur bourgeons de Picea pungens en culture in vitro

Summary Resting vegetative buds of 20-year-old Picea pungens «kosteriana glauca» were induced to form adventitious bud primordia in vitro when cultured on medium containing cytokinin. After swelling of the needle primordia and transfer of the induced buds to medium containing charcoal but lacking cytokinin, with an obligatory passage in the dark (8 days), adventitious buds developed. The adventitious buds arose from meristems formed de novo in the needle primordia as shown by anatomical data. The role of charcoal is discussed.

Interaction of polyamines or their precursors with the calcium-controlled secretion of peroxidase by sugarbeet cells

Three polyamines tested (cadaverine, spermidine and spermine) and their 2 precursors (the amino acids arginine and ornithine) inhibit the Ca2+-mediated secretion of peroxidases by sugarbeet cells in suspension culture at concentrations ranging from 10−15 to 10−5M. In the absence of exogenous Ca2+, spermine added at higher concentrations mimics the activatory effect of Ca2+, the other polyamines being without effect.

Stabilized Dormancy in Sugarbeet Fruits. III. Water Sensitivity

Removing the operculum or placing dormant sugarbeet fruits with the operculum downward on watered filter paper resulted in an increase in germination. The importance of the operculum position was reduced under optimal watering conditions for germination. The amount of imbibed water and the water layer surrounding the fruits increased with increasing amounts of bedding water. An inverse relationship between fruit germination percentage and imbibition was established. This was improved by taking into account the adhering water film.

In vitro vegetative multiplication of Fuchsia hybrida

Abstract Rapid development of axillary buds from shoot-tips and nodes of 18 cultivars of Fuchsia hybrida was obtained on solid Murashige and Skoog medium with BAP (1 mg l−1 and an auxin (0.1 mg l−1). NAA as the auxin appeared to be more active than IAA or IBA. Vegetative shoots were subsequently isolated and developed up to 15 supplementary axillary shoots on the same solid medium. Agitated and non-agitated liquid media of the same composition were less effective. One-cm long shoots could be rooted in 20 days in the presence of IBA before being transferred to soil.

Dormance stabilisée de semences de betterave sucrière: Désoperculation mécanique des fruits

Among different populations of monogerm sugarbeet fruits, those characterized by the lowest percentages of germination exhibited the lowest percentages of mechanical deoperculation (removal of the fruit cap under the sole imbitition pressure). X-ray radiography of dry fruits allowed a classification based on the space occupied by seeds inside the fruit cavity and further established a correlation between the fruit type (filled, semi-filled, empty), passive deoperculation and germination. The degree of correlation depended on the amount of bedding water which further conditioned the fruit surrounding water film.

Stabilized dormancy of sugar beet seed: mechanical decapping of the fruits.

Among different populations of monogerm sugarbeet fruits, those characterized by the lowest percentages of germination exhibited the lowest percentages of mechanical deoperculation (removal of the fruit cap under the sole imbitition pressure). X-ray radiography of dry fruits allowed a classification based on the space occupied by seeds inside the fruit cavity and further established a correlation between the fruit type (filled, semi-filled, empty), passive deoperculation and germination. The degree of correlation depended on the amount of bedding water which further conditioned the fruit surrounding water film.