An effective pistachio (Pistacia vera L.) micropropagation system was developed involving rapid axillary bud proliferation and ex vitro rooting. The highest shoot proliferation frequency was obtained from nodal explants cultured on Murashige and Skoog (MS) basal salts containing Gamborg (B 5 ) vitamins and supplemented with 4 mg l -1 6-benzyladenine (BA). The addition of 2 mg l -1 meta-topolin (mT) generated an optimal number of shoots with suitable morphological features, while kinetin (KIN) was found to be unsuitable for pistachio shoot proliferation. Microcuttings were rooted ex vitro after being dipped in rooting powder. The peak ex vitro rooting response was achieved after shoot explants were treated with Rhizopon Ò 2% indole-3-butyric acid (IBA). Rooted plantlets were transplanted in plastic pots containing a peat-perlite-vermiculite (1:1:1) mixture and then transferred to the greenhouse. After 2 months, 81.5% survival of rooted microshoots was achieved.

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Glassiness of willow (Salix babylonica L.) can be controlled by the amount of ammoniacal nitrogen in the culture medium. In this study, glutamate dehydrogenase (EC 1.4.1.3) activity was observed in the different parts of the plant during induction of the vitrification process. The apparent affinity constants of the enzyme for ammonium were determined. The root enzyme displayed the highest affinity for ammonium (Km 0.70 – 2.25 mM), and correlatively, its activity was linked to the amount of ammonium applied and to the development of the vitreous state. Although it has been shown that ethylene, matric potential and high cytokinin content are implicated in vitrification, the present study shows that a knowledge of the affinity constants for ammonium, when the ammoniacal nitrogen content of the culture medium is taken into account, can predict the risk of the plant material becoming vitreous.

Présenté par Philippe Morat RésuméAfin d'étudier la tolérance à la salinité chez le pistachier fruitier (Pistacia vera L.), des embryons isolés issues de graines matures ont été cultivés in vitro et soumis durant 30 jours à différentes concentrations salines : 0 ; 42,8 ; 85,5 ; 171,1 et 256,6 mM de NaCl. Les résultats acquis montrent que la germination in vitro des axes embryonnaires n'a pas été affectée par la concentration du sel. Cependant, le taux de survie des embryons germés passe de 100% pour le témoin à 62,9% pour la plus forte concentration saline (256,6 mM). D'autre part, l'estimation de la croissance des vitrosemis (longueur de la partie aérienne et racinaire, nombre de feuilles produites par embryon développé ainsi que la production des biomasses totales des matières fraîches et sèches de la partie aérienne et racinaire) a décelé des différences significatives pour les différentes concentrations du sel.

To enhance the induction of shoots, the excised nodes were cultured on Murashige and Skoog medium containing different cytokinins and various concentrations. The best conditions for shoot induction and growth were with 6-benzyladenine at 1.0 mg•l -1 . For axillary shoot proliferation, the excellent result was obtained using 2.0 mg•l -1 meta-topoline. Well-developed shoots (more than 2 cm in length) were successfully rooted ex vitro at 82% by treatment with commercial rooting powder (2% indole-3-butyric acid; Rhizopon ® ). Rooted plantlets were acclimatized in the greenhouse and the survival rate of transplantation reached 80%.