Anatomy and ontogeny of the pericarp of Pterodon emarginatus Vogel (Fabaceae, Faboideae), with emphasis on secretory ducts

Abstract

Discrepant and incomplete interpretations of fruits of Pterodon have been published, especially on the structural interpretation of the pericarp portion that remain attached to the seed upon dispersal. The present work clarified these doubts and analyzed ultrastructural aspects of the Pterodon emarginatus diaspores using light and transmission electron microscopes. Cell divisions are prevalent among the initial phases of development, and the subadaxial and adaxial meristems form the fibrous inner mesocarp and the endocarp composed of multi-seriate epidermis, respectively. At the median mesocarp, numerous secretory ducts differentiate between the lateral bundles, by lytic process. After lysis of the central cells and the formation of the lumen, the ducts show unistratified secretory epithelium with dense cells; oil droplets are observed on the secretory epithelium and the subadjacent tissues. At maturity, the uniseriate exocarp and the outer mesocarp slough off in an irregular fashion, leaving the diaspore composed of a papery and brittle wing linked to a seed chamber that includes the median mesocarp composed of lignified cells, bordering vascular bundles and many secretory ducts whose epithelial cells develop large vacuoles that accumulate oleoresins. The Pterodon emarginatus fruit is a cryptosamara.

Oil Glands in Pterodon pubescens Benth. (Leguminosae-Papilionoideae): Distribution, Structure, and Secretion Mechanisms

“…Secretory cavities are present in all aerial vegetative organs of adult individuals of Pterodon pubescens, as reported in other legume species (Turner 1986;Teixeira et al 2000;Teixeira and Gabrielli 2000;Marcati et al 2001;Paiva and Machado 2007;Paiva et al 2008). This study demonstrated that secretory cavities were absent in the mature embryo and were first observed in the eophylls of P. pubescens seedlings.…”

“…The ultrastructural features observed in the epithelial cells of P. pubescens, such as the proliferation of smooth endoplasmic reticulum and polymorphic plastids, are common characteristics described for oil cells in other species (Paiva and Machado 2007;Teixeira and Rocha 2009;Rodrigues et al 2011b). Proliferation of smooth endoplasmic reticulum and plastids without grana are associated with lipid synthesis (Fahn 1979;2000) and have been described for many glands secreting lipophilic substances, mainly monoterpenes (Cheniclet and Carde 1985;Monteiro et al 1999;Turner et al 1999;Machado et al 2006;Paiva et al 2008). Lipophilic droplets were observed in the cytoplasm of the epithelial cells and in the lumen of the secretory cavities in P. pubescens, by means of TEM.…”

“…As mentioned above, secretory cavities are lacking in the mature embryo. On the other hand, an abundance of oil ducts in the pericarp of the indehiscent fruit was described by Paiva et al (2008) in Pterodon emarginatus (syn. P. pubescens), and this is a protective factor that probably compensates for the absence of secretory cavities in the mature embryo.…”

“…Secretory cavities and canals are common in many members of Leguminosae and can occur in vegetative (Lersten and Curtis 1986;Turner 1986;Teixeira et al 2000;Teixeira and Gabrielli 2000;Marcati et al 2001;Paiva and Machado 2007;Rodrigues and Machado 2009;Teixeira and Rocha 2009;Rodrigues et al 2011aRodrigues et al , 2011bMilani et al 2012) or reproductive organs (Paiva et al 2008;Teixeira and Rocha 2009). These structures in legumes have taxonomic (Turner 1986;Lersten and Curtis 1996;Teixeira et al 2000;Gabrielli 2000, 2006), ecological (Langenheim et al 1982;Arrhenius and Langenheim 1983;Langenheim 2003), and economic (Coelho et al 2001;Langenheim 2003;Plowden 2003) aspects.…”

Oleoresin glands in copaíba (Copaifera trapezifolia Hayne: Leguminosae), a Brazilian rainforest tree

“…The occurrence of canals (elongated lumen) and cavities (isodiametric lumen) was recorded in species of Caesalpinia sensu Bentham (Lersten and Curtis 1994), Copaifera (Alencar 1982;Marcati et al 2001;Rodrigues and Machado 2009;Rodrigues et al 2011), Dahlstedtia (Teixeira and Gabrielli 2000), Hymenaea (Lee and Langenheim 1975;Paiva and Machado 2007), Lonchocarpus , Myrocarpus, Myrospermum, Myroxylon (Sartori and Tozzi 2002), and Pterodon (Paiva et al 2008). Such structures are reported for all plant organs, especially the aerial (Teixeira and Gabrielli 2000;Paiva and Oliveira 2004;Rodrigues and Machado 2009;Rodrigues et al 2011), and originate from protoderm cells (Turner 1986;Paiva and Machado 2007) or ground meristem (Teixeira and Gabrielli 2000;Teixeira and Rocha 2009).…”