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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Explaining Ovule Sterility in Rauvolfia L. (Apocynaceae)

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Souto, Letcia S. [1] ; Koch, Ingrid [2]
Total Authors: 2
[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
Total Affiliations: 2
Document type: Journal article
Source: INTERNATIONAL JOURNAL OF PLANT SCIENCES; v. 179, n. 5, p. 368-376, JUN 2018.
Web of Science Citations: 0

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)

FAPESP's process: 15/01424-4 - Sporogenesis and gametogenesis of Rauvolfia l. species (Apocynaceae) with report of monoecy, dioecy and ginodioecy
Grantee:Letícia Silva Souto
Support type: Regular Research Grants