In vitro growth and organogenesis of Prosopis farcta plantlets (Fabaceae, Mimosoideae) in culture medium supplemented with various concentrations of Ca++ and Na+.

The objective of this study was to vary the mineral composition of the culture medium of Prosopis farcta seedlings per addition of Na+ and Ca++ ions with the aim to identify the culture media which support the growth and/or the expression of the in vitro plant organogenesis. The Na+ and Ca++ ions were added in the culture medium in various concentrations by taking the Gamborg medium, in which macroelements were diluted 10 times, as the basic one. After two months of culture, parameters relating to the vegetative development of plant seedlings and to the various expressions of organogenesis were measured. Weak concentrations in sodium and calcium ions as well as a weak concentration in Ca++ (0.1 mM) with 50 mM in Na+ support the best vegetative development of the plantlets. The most important percentage of plant seedlings presenting a bud initiation was obtained on a medium containing 0.1 mM of Na+ and 50 mM of Ca++. Our study defined several media likely to support in vitro development of Prosopis farcta plantlets allowing the selection of salt tolerant plants or cellular lines. Some other media were chosen for improving micropropagation of the species without adding growth substances.

[Polygamy in Atriplex halimus L. (Chenopodiaceae)]. / Polygamie chez Atriplex halimus L. (Chenopodiaceae).

It appears that up to now the inflorescence and flower morphologies of Atriplex halimus have been described incompletely. This species has been classified as monoecious or dioecious. Numerous observations and ontogenic studies have pointed to types of flowers morphologically and functionally hermaphroditic, never described until now. One specimen of this species presents both unisexual, male and female flowers and bisexual flowers, so Atriplex halimus is polygam and more precisely trimonoecious. Observation of inflorescences reveals a structure based on the spike and the dichasium. The sex distribution along the inflorescence axis was studied and the existence of a physiological gradient controlling its expression is discussed.