Jean-Claude Audran

Characteristics of the Photosynthetic Apparatus and CO2-Fixation in the Flower Bud of Lilium. I. Corolla

In order to test the positive net CO2-fixation ability of tepals in the flower bud of Lilium hyb. enchantment, photoautotrophic characters were studied during pollen development in tepals and then compared with those in the leaf. Although mesophyll structure, plastid ultrastructure, stomata density, and chlorophyll content were significantly different in both organs, tepals performed positive net CO2-fixation from the microspore mother cell stage up to pollen mitosis but not during pollen maturation. The measurements of CO2-fixation were performed in the linear part of the saturation curve of the L5 leaf at 100 μmol photon m-2 s-1. In the tepals, CO2-fixation} reached its maximal intensity at the tetrad stage with 1.83 ± 0.12 μmol CO2 m-2 s-1, against 3.17 ± 0.27 μmol CO2 m-2 s-1 in the L5 leaf. Under these conditions, tepal CO2-fixation corresponded to 57.7% of the leaf assimilation, whereas the maximum chlorophyll concentration in the tepal represented 21.9% of the chlorophyll concentration in the leaf. The flower bud of Lilium may be considered not solely as a sink structure for the whole plant but also as a partly autonomous organ in terms of photosynthates.

Orbicule wall surface characteristics in Lilium (Liliaceae)

Abstract In Lilium cv. enchantment, an orbicule peripheral sheet is characterized. It is 10 nm thick and surrounds the whole Ubisch body. Ultrastructural and cytochemical observations allow us to propose that the orbicule peripheral sheet represents remnants of a glycocalyx supported by the membrane limiting orbicule core on which sporopollenin is synthesized. A model of orbicule sporopollenin architecture and biosynthesis is discussed.

Electron microscope evidence for a membrane around the core of the Ubisch body in Lilium (Liliaceae)

Abstract Ultrastructural and cytochemical studies have shown that the orbicule core is surrounded by a sheet about 90 A in thickness. It is stained by KMnO4 and composed of proteins, unsaturated lipids and esterified pectins. These data indicate that there is a biological membrane between the orbicule core and the wall. It is thought that this membrane is coated by a glycocalyx and supports the orbicule sporopollenic wall biosynthesis.

Cytochemical and infrastructural aspects of pollen and tapetum ontogeny in silene dioica (caryophyllaceae)

Abstract Cytochemical modifications and ultrastructural transformations of pollen and tapetum were studied in Silene dioica (L.) Clairv. Meiosis leads to the formation of simultaneously septated tetrads. Ectexine is elaborated under the callose wall within a polysaccharic, fibrillar primexine. Endexine is formed after dissolution of the callose wall. During the vacuolization and enlargement of the microspores the structure and the chemical composition of the exine are modified. The tapetum is of the secretory type. Its cell walls are destroyed as soon as the tetrad stage is completed. Orbicules of large size and irregular shape are formed in the periplasmic spaces. Tapetal cells are modified, liberating a quantity of tryphine in the anther loculus.

La stérilité mâle nucléo-cytoplasmique chez la féverole (vicia faba l). ix

Abstract The main stages of sporoderm ontogenesis in fertile Faba bean are at once shown like reference. In these plants, five running periods are recognized in the tapetum activity: 1) after the break-up of tetrads and the release of microspores in the anther cavity, the Vicia faba tapetum presents an important secretory activity and its inner plasmalemma gets wavy. In the crypts thus formed and along the plasmalemma inner face a fibrillar network is developing, limited from the loculus by a thin pellicle with which it is in continuity. This whole structure constitutes the tapetum glycocalyx and reacts positively with ferric hydroxylammonium, PTA at low pH, PTA-acetone and PATAg; 2) at unpolarized microspore stage, many lipid droplets are accumulated in glycocalyx; 3) at polarized microspore stage, numerous membranous formations (F.M.), sometimes in continuity with the plasmalemma, are formed in the tapetum glycocalyx. In sixteen stamens on thirty, orbicules are not formed but the F.M. move in the anther...