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| Author(s): |
Stefany Cristina de Melo Silva
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Botucatu. 2019-04-04. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu |
| Defense date: | 2019-02-28 |
| Advisor: | Tatiane Maria Rodrigues |
| Abstract | |
Extrafloral nectaries (EFNs) are common and morphologically diverse in Cactaceae, and may be highly modified spines or not, scamiform leaves and specialized epidermal and cortical regions located at the base or around the areoles. However, little is known about the nature of EFNs in cacti, and even if the exudate can be qualified as nectar. We aimed to analyze the morphology, anatomy and ultrastructure of the secretory spines in Brasiliopuntia brasiliensis and Nopalea cochenillifera and the chemical composition of the secretion. Secretory spines were processed for light (bright field and confocal) and scanning and transmission (conventional and cytochemical) electron microscopy. The composition of sugars and amino acids was analyzed by high performance liquid chromatography (HPLC). Field observations have shown that the exudate accumulated at the apex of the spines is removed by ants. The ontogenetic, structural and functional aspects of the secretory spines were similar in both species. Secretory spines originate from the areolar meristem, beginning as small protuberances formed by protoderm and fundamental meristem. Spines in the secretory phase presented a) dilated base filled by small cells with thin pecto-cellulosic walls, dense cytoplasm and voluminous nucleus; b) elongated median region composed of fibriform cells with non-lignified walls; and c) apical portion tapered with fusiform cells with non-lignified walls. Vascular tissues are present in the basal region of the spines. Ultrastructurally, the cells of the basal region presented irregular shape and walls with wide plasmodesmata; the middle lamella is swollen at the angles between the cells; mitochondria, rough endoplasmic reticulum, polyribosomes, plastids and abundant dictyosomes occurred in the cytoplasm. The cytochemical analyzes allowed us to identify the dictiosomal origin of vesicles found in the cytoplasm of these cells and the mechanism of secretion release via exocytosis. Chemical analyzes indicated that the exudate released by the secretory spines is rich in sugars; in both species the exudate was sucrose-dominant and with a similar amino acid profile. Our results indicated the occurrence of intense synthesis of hydrophilic substances confirming that these spines are extrafloral nectaries. (AU) | |
| FAPESP's process: | 17/14891-5 - Anatomical, chemical and ultrastructural characterization of secretory spines in two Cactaceae species |
| Grantee: | Stefany Cristina de Melo Silva |
| Support Opportunities: | Scholarships in Brazil - Master |