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Pericarp and seed coat structure in Tapirira guianensis (Spondiadeae: Anacardiaceae)

1990; Elsevier BV; Volume: 56; Issue: 4 Linguagem: Romeno

10.1016/s0254-6299(16)31038-9

1727-9321

Irmgard von Teichman,

Botanical Research and Applications

Tapirira guianensis Aubl., a member of the Anacardiaceae from tropical South America, is characterized by a fleshy drupe with a relatively large, partially pachychalazal, exalbuminous seed. A distinctive feature of the exocarp sensu lato is the hypodermis with thickened secondary cell walls, whereas the mesocarp is a typical sarcocarp. The relatively weakly developed endocarp sensu lato, which does not differentiate any opercula, differs significantly from the massive, operculate endocarp reported for other members of the Spondiadeae. Structurally the seed coat of T. guianensis resembles that of related genera. The seed coat is of dual origin as it develops from the integument and the chalaza. It is undifferentiated in the sense that it lacks a definite mechanical layer. Species-specific differences in the Spondiadeae include the cell wall components of the hypostase, namely specific polysaccharides, phenolic compounds and callose. These unique features of the exocarp and seed coat of T. guianensis may possibly constitute an alternative evolutionary strategy within the Spondiadeae towards the protection of the embryo. Tapirira guianensis Aubl., 'n lid van die Anacardiaceae van tropiese Suid-Amerika, word gekenmerk deur 'n vlesige steenvrug met 'n relatief groot, gedeeltelik pagichalasale endospermlose saad. 'n Onderskeidende kenmerk van die eksokarp sensu lato is die hipodermis met verdikte sekondêre selwande, terwyl die mesokarp 'n tipiese sarkokarp is. Die relatief swak-ontwikkelde endokarp sensu lato, wat geen operkulums differensieer nie, verskil betekenisvol van die omvangryke endokarp met operkulums wat by ander lede van die Spondiadeae aangeteken is. Struktureel stem die saadhuid van T. guianensis grootliks ooreen met dié van verwante genusse. Die saadhuid is van tweeledige oorsprong aangesien dit vanuit die integument en chalasa ontwikkel. Dit is ongedifferensieerd in die sin dat 'n definitiewe meganiese laag ontbreek. Die spesiespesifieke verskille in die Spondiadeae behels hoofsaaklik die selwandbestanddele van die hipostase, naamlik spesifieke polisakkariede, fenoliese verbindings en kallose. By die Spondiadeae mag dié unieke kenmerke van die eksokarp en saadhuid van T. guianensis moontlik 'n alternatiewe evolusionêre strategie verteenwoordig wat die beskerming van die embrio verseker.