Polyamine metabolism and in vitro cell multiplication and differentiation in leaf explants of Chrysanthemum morifolium Ramat

Organogenesis fromSolanum melongena L. (eggplant) cotyledon expiants is associated with hormone-modulated enhancement of polyamine biosynthesis and conjugation

“…In our experience, treatment with this inhibitor was highly deleterious towards rhizogenesis and explant growth; effects were only slightly reverted by addition of 1 mM Put (data not shown), and thus difficult to interpret as a specific response to altered Put metabolism. Some authors have provided correlative evidence for the positive involvement of Spd in the initiation of adventitious buds (Bagni et al 1993, Tanimoto et al 1994, Aribaud et al 1994. Also in the present work, free-Spd levels in caulogenic explants were always higher than in rhizogenic ones.…”

“…As previously reported for some in vitro cultured plant tissues (Aribaud et al 1994, Altabella et al 1995 but not others (Tiburcio et al 1988, Feirer et al 1984, ODC markedly prevailed over ADC activity, the former considered the enzyme associated with cell division (Cohen etal. 1982).…”

“…Similar results were obtained by us even though the auxin and cytokinin used were different. In leaf explants of Crysanthernurn rnorifolium, conjugates also appeared on all hormone-supplemented media after 2 days in culture and levels were strongly influenced by the hormonal treatment (Aribaud et al 1994). In particular, both Put and Spd conjugates accumulated to much higher levels in the presence of indoleacetic acid (rootforming medium) compared with BA (shoot-forming medium).…”

“…With the aim of maintaining high levels of Put, eggplant explants grown on rooting medium were also treated with [3-OH-ethylhydrazine, an inhibitor of DAO activity. In Crysanthemum leaf discs induced to form buds (Aribaud et al 1994) or roots (Martin-Tanguy et al 1997), addition of 2 mM [3-OH-ethylhydrazine markedly enhanced Put content and blocked organogenesis totally. The latter authors suggested that DAO-mediated Put catabolism is involved in root induction in this material.…”

“…Other approaches essentially rely on the use of PA biosynthesis inhibitors, application of exogenous PAs, and correlative data on temporal and spatial changes in PA levels associated with the different phases of morphogenesis. In a few cases, regenerating and nonregenerating explants of the same species (Aribaud et al 1994, Martin-Tanguy et al 1988, or even tissues of the same explant (Leshem et al 1991, Pedroso etal. 1997, have been comparatively analysed.…”