Changes in Abscisic Acid Content in Axis and Cotyledons of Developing Phaseolus vulgaris Embryos and their Physiological Consequences

Prevost, I. and Le Page–Degivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.—J.exp. Bot. 36: 1900–1905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radio–immunoassay.During embryogenesis, a similar pattern was observed in bothtissues: ABA increased to a maximum 29 d after an thesis, followedby a decrease as the seed matured. The level of ABA in the cotyledonswas always much higher than that in the axes. In in vitro cultures,the duration of the lag phase before germination of isolatedembryonic axes increased with ABA content. The presence of cotyledonsalways lengthened the lag phase; longer lag phases were associatedwith greater concentrations of ABA in the cotyledons. Moreoverthe presence of cotyledons stimulated the growth of seedlings. Key words: ABA distribution, embryo maturation, axis and embryo germinability     

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.     

Acides aminés libres et protéiques des divers types de rameaux du Periploca graeca: Rôle dans la circumnutation des tiges volubiles et compartimentation intracellulaire

Free and Bound Amino Acids in the Different Shoot Types of Periploca graeca: Role in the Circumnutation of Twining Shoots, and Cellular Compartmentation. A study has been made of amino acids of wall proteins, cytoplasmic TCA insoluble proteins and proteins of organelles in growing tissues from three types of shoots: short upright, twining, and creeping, all carried by the same specimen of Periploca graeca L. Each shoot type presents a specific pattern. The twining shoots are very rich in cytoplasmic TCA-insoluble proteins. The upright shoots distinguish themselves by a high level of proteins in the organelles and in the cell-wall. However, the composition of wallproteins is almost the same in the three types of shoots. This result excludes the existence of particular wall proteins (extensin, for example) in the twining and rapidly growing shoots. In these shoots the high level of free prolin is not a consequence of low incorporation in the proteins. Distribution of prolin, aspartic acid and glutamic acid between the cellular compartments (wall, hyaloplasm and organelles) has a specific pattern in each shoot type.     

Resistance of Drosophila suzukii to the larval parasitoids Leptopilina heterotoma and Asobara japonica is related to haemocyte load

Unlike other Drosophila species, the invasive Drosophila suzukii Matsumura (Diptera: Drosophilidae) shows a remarkable pest status. Among the physiological traits that may explain the high level of resistance to parasitoids of Drosophila larvae, the haemocyte load is shown repeatedly to play an important role. To determine whether haemocyte load can explain immunity resistance of D. suzukii to parasitoids, the haemocytes of parasitized and healthy larvae are quantified in two Japanese and three French populations of D. suzukii. Parasitization tests are conducted with two larval parasitoids: the paleartic Leptopilina heterotoma Thomson (Hymenoptera: Figitidae) and the Asian Asobara japonica Belokobylskij (Hymenoptera: Braconidae). Based on morphological and functional criteria, D. suzukii has classes of haemocytes similar to those described in Drosophila melanogaster. However, healthy larvae of the five populations tested possess particularly large numbers of haemocytes compared with D. melanogaster. Haemocyte load is also higher in larvae from the French populations than in the Japanese strains. The ability of D. suzukii larvae to encapsulate eggs of L. heterotoma is associated with a particularly high load of circulating haemocytes. However, it is notable that A. japonica induces a strong depression of the haemocyte population in this resistant host associated with an inability to encapsulate parasitoid eggs. The results show that the cellular immune system plays a major role in the failure of larval parasitoids to develop in most instances in larvae of D. suzukii, possibly contributing to the success of this species as an invader.     

Inverse Correlation between ABA Content and Germinability throughout the Maturation and the In Vitro Culture of the Embryo of Phaseolus vulgaris

Prevost, I. and Le Page-Degivry, M. Th. 1985. Inverse correlationbetween ABA content and germinability throughout the maturationand the in vitro culture of the embryo of Phaseolus vulgaris.—J.exp. Bot. 36: 1457–1464. Changes in embryo abscisic acid (ABA) content during the maturationof the seed of Phaseolus vulgaris cv. Contender were followed,using a radio-immunoassay. The pattern of change is similarto that already described in several species: a rapid increase(from the 18th to 29th day after anthesis), was followed bya decrease, the ABA level being ten times lower on the 48thday than on the 29th. Embryos isolated from the 18th to the48th day after anthesis were able to ‘germinate’when cultivated on a mineral medium supplemented with sucroseand agar. The development pattern varied throughout the embryogenesisand could be correlated with the differentiation of the embryoat the time of isolation. Before germination could take place,we observed a lag phase, the duration of which could be correlatedwith embryo ABA content. As ABA content increased in the youngestembryos the duration of the lag phase increased. In the sameway, the number of days to germination was shown to diminishas ABA content decreased. Inverse correlation between ABA contentand germinability was thus demonstrated throughout the developmentof the embryo. During in vitro culture, free ABA content decreased in the embryoand reached low values a few days before germination occurred.So the beginning of root elongation in culture was again wellcorrelated with the disappearance of free endogenous ABA. Atransfer experiment inducing an earlier germination associatedwith a more limited development suggests that the lag phaseis associated with an active continuation of embryonic development Key words: Embryo maturation, abscisic acid, germinability     

Mise en Évidence d'un Effet Régulateur de la Proline Exogène sur le Cycle du Glycolate Chez Nicotiana tabacum cv. Xanthi

Demonstration of a regulatory effect of exogenous proline on the glycolate cycle 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 leaf disks of vegetative Nicotiana tabacum cv. Xanthi n.c. The same phenomenon does not occur in the equivalent tissues of tobacco plants after floral induction, these being naturally rich in proline. Under different environmental conditions (light, dark, varying concentrations of CO₂ and O₂), the exogenous proline appears to modify one or more reactions of the glycolate pathway.