Morphological and secretory characterization of extrafloral nectaries in plants of coastal Veracruz, Mexico.
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BACKGROUND AND AIMS: Morphological descriptions of the extrafloral nectaries (EFNs) of certain plant species are common in the literature, but they rarely relate morphology with histology, gland distribution and secretory attributes. In this study a morphological/secretory characterization of EFNs occurring on several plant species in a tropical coastal community is made and the implications of gland attributes discussed from a functional perspective. METHODS: The morphology and nectar secretion of the EFNs of 20 plant species are characterized through scanning electron microscopy, histochemical detection of reducing sugars (Fehling's reagent) and nectar volume/concentration estimates. KEY RESULTS: Sixty-five per cent of plant species in coastal communities had EFNs on vegetative structures and 35 % of species had glands on reproductive and vegetative organs. The Fabaceae is the plant family with the most species with EFNs and most diversity of gland morphologies. Four types of vascularized nectaries and four of glandular trichomes are described; sugar-secreting trichomes are characterized using Fehling's technique, and the first descriptions of unicellular and peltate trichomes functioning as EFNs are provided. Glands of ten plant species and six genera are described for the first time. Four plant species possess more than one morphological type of EFN. Eleven species have EFNs in more than one location or organ. More complex glands secrete more nectar, but are functionally homologous to the aggregations of numerous secretory trichomes on specific and valuable plant organs. CONCLUSION: Important diversity of EFN morphology was foundin the coastal plant community studied. Both vascularized and non-vascularized EFNs are observed in plants and, for the latter, previously non-existent morpho-secretory characterizations are provided with a methodological approach to study them. It is recommended that studies relating EFN attributes (i.e. morphology, distribution) with their differential visitation by insects (i.e. ants) and the cost of maintenance to the plants are carried out to understand the evolution of these glands. (+info)
Quantitative determination of incarvillateine in Incarvillea sinensis by solid phase extraction and high performance liquid chromatography.
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Method for rapid quantitative analysis of incarvillateine in Incarvillea sinensis by high-performance liquid chromatography (HPLC) has been developed. The sample preparation involves solid phase extraction (SPE) with a mixed-mode reversed-phase and cation-exchange cartridge. The linear calibration range for incarvillateine was 0.002-0.5 mg/ml. The limit of detection was 0.35 microg/ml (S/N=3). Intra- and interday precisions were less than 0.36% (n=6) and 1.61% (n=18), respectively. The recovery of incarvillateine was 97.61-102.44% with the relative standard deviation (RSD) ranging from 0.63 to 1.93% (n=3). This method was proposed as a simple, rapid and accurate method for quantitative determination of incarvillateine content in various samples of Incarvillea sinensis collected from different areas of China. (+info)
Ovary peltate trichomes of Zeyheria montana (Bignoniaceae): developmental ultrastructure and secretion in relation to function.
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BACKGROUND AND AIMS: Nectar production in the Bignoniaceae species lacking a nectariferous functional disc is ascribed to trichomatic glands around the ovary base and/or on the inner corolla wall. Nevertheless, knowledge about the secretion and function of these glands is very incomplete. The purpose of this paper is to study, from a developmental viewpoint, the ultrastructure, histochemistry and secretory process of the peltate trichomes on the ovary of Zeyheria montana, a species in the Bignoniaceae which has a rudimentary disc. METHODS: Samples of the gynoecium at various developmental stages were fixed and processed for light and electron microscopy. Histochemistry and cytochemistry tests were performed to examine the chemical composition of exudates. Thin layer chromatography was used to determine the presence of alkaloids and terpenes in gynoecium and fruit extracts, and in fresh nectar stored in the nectar chamber. KEY RESULTS: Peltate trichomes at different developmental stages appear side by side from floral budding up to pre-dispersal fruit. Large plastids with an extensive internal membrane system consisting of tubules filled with lipophilic material, abundant smooth endoplasmic reticulum, few Golgi bodies, lipophilic deposits in the smooth endoplasmic reticulum and mitochondria, and scattered cytoplasmic oil droplets are the main characteristics of mature head cells. The secretion which accumulates in the subcuticular space stains positively for hydrophilic and lipophilic substances, with lipids prevailing for fully peltate trichomes. Histochemistry and thin layer chromatography detected terpenes and alkaloids. Fehling's test to detect of sugars in the secretion was negative. CONCLUSIONS: The continuous presence and activity of peltate trichomes on the ovary of Z. montana from early budding through to flowering and fruiting set, and its main chemical components, alkaloids and terpenes, suggest that they serve a protective function and are not related to the floral nectar source or to improving nectar quality. (+info)
Constituents from the bark of Tabebuia impetiginosa.
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Thirteen new phenolic glycosides were obtained by further study of constituents from the bark of Tabebuia impetiginosa (MART. ex DC) Standley (Bignoniaceae). The structures of these compounds were determined based on NMR, mass spectral and chemical evidence. Most of them have a glycosyl unit esterified by a benzoic acid derivative. (+info)
Trypanocidal activity of triterpenes from Arrabidaea triplinervia and derivatives.
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Ethanol extract from Arrabidaea triplinervia leaves showed in vitro activity (ED100 5.0 mg/ml) against trypomastigotes of Trypanosoma cruzi, the etiologic agent of Chagas; disease. Bioactivity-directed fractionation of this extract led to the isolation of ursolic and oleanolic acids as trypanocidal compounds besides pomolic acid (not tested) and alpinetine (inactive). A series of natural and synthetic derivatives of ursolic and oleanolic acids was simultaneously assayed for structure activity relationships (SAR) studies. Ursolic acid (ED100 0.4 mg/ml) was four times more active than oleanolic acid (ED100 1.6 mg/ml). The presence of free hydroxy and/or carboxy groups is necessary for the trypanocidal activity as could be deduced from the effect of the acetates, methyl ester, and aldehyde derivatives. (+info)
Wind-dragged corolla enhances self-pollination: a new mechanism of delayed self-pollination.
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BACKGROUND AND AIMS: Delayed self-pollination is a mechanism that allows animal-pollinated plants to outcross while ensuring seed production in the absence of pollinators. This study aims to explore a new mechanism of delayed self-pollination facilitated by wind-driven corolla abscission in Incarvillea sinensis var. sinensis. METHODS: Floral morphology and development, and the process of delayed self-pollination were surveyed. Experiments dealing with pollinator and wind exclusion, pollination manipulations, and pollinator observations were conducted in the field. KEY RESULTS: Delayed self-pollination occurs when the abscising corolla driven by wind drags the adherent epipetalous stamens, thus leading to contact of anthers with stigma in late anthesis. There is no dichogamy and self-incompatibility in this species. The significantly higher proportion of abscised corolla under natural conditions as compared with that in wind-excluding tents indicates the importance of wind in corolla abscission. When pollinators were excluded, corolla abscission significantly increased the number of pollen grains deposited on the stigma and, as a result, the fruit and seed set. Only half of the flowers in plots were visited by pollinators, and the fruit set of emasculated flowers was significantly lower than that of untreated flowers in open pollination. This species has a sensitive stigma, and its two open stigmatic lobes closed soon after being touched by a pollinator, but always reopened if no or only little pollen was deposited. CONCLUSIONS: This delayed self-pollination, which involved the movement of floral parts, the active participation of the wind and sensitive stigma, is quite different from that reported previously. This mechanism provides reproductive assurance for this species. The sensitive stigma contributes to ensuring seed production and reducing the interference of selfing with outcrossing. The pollination pattern, which combines actions by bees with indirect participation by wind, is also a new addition to ambophily. (+info)
Anther appendages of Incarvillea trigger a pollen-dispensing mechanism.
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