Explaining Ovule Sterility in Rauvolfia L. (Apocynaceae)

Autor(es)

Souto, Letcia S. ^[1] ; Koch, Ingrid ^[2]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Carlos, Ctr Ciencias Humanas & Biol, Dept Biol, Lab Diversidade Vegetal, Campus Sorocaba, Sorocaba, SP - Brazil

^[2] Univ Estadual Campinas, Inst Biol, Dept Biol Vegetal, Lab Taxon, CP 6109, BR-13083970 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: INTERNATIONAL JOURNAL OF PLANT SCIENCES; v. 179, n. 5, p. 368-376, JUN 2018.
• Citações Web of Science: 0

Resumo

Premise of research.Approximately 5% of Gentianales are estimated to be dioeciousmainly the members of Rubiaceae, Gentianaceae, and Loganiaceae. In Apocynaceae, there exists a report of cryptic dioecy for Rauvolfia sellowii Mull. Arg. Some individuals have flowers with empty anthers (pistillate), and some have flowers with ovules that do not develop into seeds (staminate). As the staminate flowers in this species appear to be hermaphrodite, embryology could help explain how ovule sterility occurs. We aim to identify how the development of ovules, megasporogenesis, and megagametogenesis occur in Rauvolfia species with different reproductive strategies and thus to determine the process that leads to ovule sterility in the staminate flowers of R. sellowii.Methodology.Floral buds and flowers were collected, fixed in Karnovsky solution for 48 h, dehydrated, embedded, sectioned, and stained with a 0.05% toluidine blue aqueous solution.Pivotal results.The species studied have two ovules per locule, except for R. sellowii, whose carpels each have up to four ovules. The ovules are anatropous, unitegmic, and tenuinucellate. The single archesporial cell differentiates directly into the megaspore mother cell, which then gives rise to a linear or T-shaped tetrad. The chalazal megaspore is functional and develops into a Polygonum type of megagametophyte. In the staminate flowers of R. sellowii, megasporogenesis is similar, but most megaspores may degenerate. When the megaspores develop, the megagametophyte can degenerate. If the megagametophyte is formed at maturity, it is narrower than those observed in the hermaphrodite flowers of the other species and shows evidence of cell death.Conclusions.Sterility of ovules in the staminate flowers of R. sellowii is due to the nonformation of functional megagametophytes but does not affect ovule formation, per se. This phenomenon can lead to a misinterpretation of the staminate flowers as being hermaphrodite. We also discuss a possible lability in the sexual expression of R. sellowii. (AU)

• Processo FAPESP: 15/01424-4 - Esporogênese e gametogênese em espécies de Rauvolfia l. (Apocynaceae) monóicas, dióicas e ginodióicas
• Beneficiário: Letícia Silva Souto
• Modalidade de apoio: Auxílio à Pesquisa - Regular