The chloroplastic atpB-rbcL spacer and the first 53 codons of the rbcL coding sequence was sequenced for 40 apple cultivars and 15 wild species. This chloroplast DNA region is 904 base pairs long, and only five mutations sites were found among the tested samples. Although the cpDNA variation was low, some parentages are proposed based on the maternal inheritance of plastid DNA: the male and female parents are specified, or else suggested, for Worcester, Discovery, Starking, Starkrimson, Kidd's Orange Red, Priscilla, and Gloster, as well as for the putative wild origin for Malus x domestica.

Summary — The type of carbohydrate used in the medium influenced the proliferation of Malus Jork 9. The microcuttings obtained showed marked differences in rooting ability. During proliferation, sorbitol (0.176 M)

Root formation in shoot cuttings of soybean (Glycine max L. `Williams'), mungbean (Phaseolus aureas Mdlbg.), English ivy (Hedera helix L.), and apple (Malus ×domestica Borkh. `Jork 9') was stimulated by dithiothreitol and reduced glutathione in the presence and absence of auxin (IAA) shock. In soybean, in the absence of auxin, root formation was stimulated to about the same extent by glutathione alone as with auxin alone. The roots induced by thiol compounds were longer than roots induced by auxin shock and were completely normal in appearance. Roots produced with auxin shock alone were short and exhibited characteristic auxin-induced deformations. With a combination treatment of auxin shock and thiol compounds, roots were more numerous than with either alone, somewhat longer than with auxin alone, and exhibited fewer of the usual deformations characteristic of roots grown in the presence of external auxins. The thiol compounds also were beneficial for rooting Malus shoots propagated from callus in vitro. The thiol compounds were most beneficial with older cuttings where auxin shock was often insufficient to obtain roots. In shoots where rooting was stimulated by thiol agents, shoots grew more rapidly than in those where rooting was induced by auxin shock alone. These findings suggest a use for thiol compounds alone or in combination with auxin shock to induce differentiation of root primordia as well as for stimulation of root growth. Chemical name used: indole-3-acetic acid (IAA).

Node cuttings of 'in vitro' cultured grapevine were rooted in absence of any growth regulator, before the onset of the axillary bud. There were two peaks of ethylene production at 2 and 10-12h, well marked in the top and bottom portions of the cuttings for the former. The level of IAA increased in the basal portions of the cuttings only, from the 4th hour, and culminated at the 24th hour. The wound ethylene of the first rise might be initiating the sequence of reactions leading to root formation. The second ethylene rise might result from the beginning of the increase of the IAA level.

Shoot microcuttings of Malus domestica cv. Jork 9, Malus domestica cv. Cepiland, Mandevilla (Dipladenia) sanderi, and Daphne odora cv. variegata were induced to root by the addition of 0.1-1 mM dithiothreitol following an auxin (indole-3-acetic acid) treatment to initiate root formation. The most difficult to root, Malus domestica cv. Cepiland, required higher dithiothreitol concentrations to achieve optimum rooting than did the less difficult to root, Malus domestica cv. Jork 9, Mandevilla sanderi, or Daphne odora variegata. The roots induced by the combination of dithiothreitol and auxin treatment were approximately twofold longer and more robust than those induced with auxin treatment alone. The combination treatment of auxin and dithiothreitol has the potential to be of practical importance in root initiation in difficult-to-root cuttings of both woody and herbaceous horticultural varieties.

L'analyse des aptitudes morphogénétiques de boutures-rosettes d'artichaut (Cynara scolymus L.) au fil de la multiplication végétative in vitro permet de montrer une réacquisition progressive de propriétés proches de celles de boutures-rosettcs obtenues sur des plantes issues de graines. Les réponses aux tests d'enracinement et de callogenèse montrent une sensibilisation progressive des fragments aux divers traitements rhizogènes. L'adjonction d'ergocalciférol (vitamine D 2) au meilleur traitement auxinique permet de stimuler les réponses rhizogènes tout en diminuant l'aptitude callogènc. L'utilisation de l'évolution de l'activité peroxydasique, comme marqueur, se révèle particulièrement adéquate pour apprécier les potentialités des boutures-rosettes soumises au traitement rhizogène optimal. Les réponses aux tests morphogénétiques et l'analyse de l'évolution de l'activité peroxydasique permettent de montrer, avec certitude, qu'il y a retour vers un fonctionnement du type de celui de la jeune plante issue de la graine au fil des cultures successives réalisées in vitro. Mots clés additionnels : Multiplication conforme, rajeunissement, peroxydases, ergocalciférol, acide naphtalène aeétique. SUMMARY Peroxidase activity and rhizogenesis in Cynara scolymus L. : changes during in vitro subculture and comparison with young plants from seed. Analysis of the morphogenetic aptitudes of rosette cuttings of artichoke (Cynara scolymus L.) during in vitro vegetative multiplication has shown progressive reacquisition of properties close to those of rosette cuttings obtained from plants arising from seeds. The responses to the rooting and callogenic tests showed progressive sensitization of the fragments to various rhizogenic treatments. The addition of ergocalciferol (Vitamin D 2) to the best auxin treatment led to stimulation of the rhizogenic responses while decreasing callogenesis. Peroxidase activity was particularly useful as a marker to assess the potentialities of rosette cuttings undergoing the optimal rhizogenic treatment. The morphogenetic tests and the peroxidase analyses showed, with a high degree of certainty, that there is a return, during successive cultures in vitro, to a mode of functioning similar to that of the young plant arising from seed.

No abstract