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sur le développement des zones arides et semi-arides

Titre : Some reproductive aspects of three Chihuahuan Desert Nyctaginaceae

Auteur : Delson RK.

Université de soutenance : New Mexico State University

Grade : Master of Science (MS) 1975

Résumé
The distribution of all three of the Nyctagineaceae species studied, Ammocodon chenopodiodes, Selinocarpus lanceolatus and Acleisanthes longiflora, is centered in the Chihuahuan Desert. All three genera regularly produce cleistogamous flowers, flowers in which the corolla does not open, but which, nevertheless, produce fruit and seeds as a result of self-fertilization. The relative frequency of cleistogamous and chasmogamous flowers (open flowers capable of outcrossing) is examined. Acleisanthes and Selinocarpus shift from a high percentage of cleistogamous flowers in late spring to a high percentage of chasmogamous flowers in summer. This shift appears to be co-ordinated with the onset of the summer rains and possibly with the presence of their pollinator, the hawk moth. The proportion of chasmogamous flowers on Ammocodon plants changes throughout a growing season, although the change is not neccessarily the same in all populations. The absence of a distinct shift in the proportion of chasmogamy in Ammocodon may be due to the fact that, in comparison with the other two species, Ammocodon is pollinated by a general array of insects and therefore not dependent on a specific pollinator. Cleistogamy in all three species appears to insure seed-set, with a relatively small expenditure of energy to the plant, under conditions unsuitable for cross-pollination

Mots Clés : Nyctaginaceae, reproduction, plant, Ammocodon, plant ,Acleisanthes, Selinocarpus,

Jornada NMSU

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