Tonka Bean Research Articles

Concentration of photosynthetic pigments and chlorophyll fluorescence of mahogany and tonka bean under two light environments

This study was carried out in a plantation of a degraded area in Central Amazon, Brazil, in order to assess environmental light effects on leaf pigment concentrations and chlorophyll a fluorescence in mahogany (Swietenia macrophylla King) and tonka bean (Dipteryx odorata Aubl. Willd). Three-year old saplings were grown in an open site (sun) with maximum radiation of approximately 2000 mumol m-2 s-1 and under the shade of a Ochroma pyramidale (Cav. ex Lam. Urb) canopy. A leaf area index of 2.46 was optically determined for the Ochroma foliage with 13% of full sunlight (maximum radiation about 260 mumol m-2 s-1). Carotenoid and chlorophyll concentrations were spectrophotometrically determined. Initial (Fo), maximum (Fm) and variable fluorescence (Fv) were determined with a portable fluorometer. Chlorophyll concentrations (Chl a, Chl b and Chl tot) on a fresh mass basis were greater in shade leaves than in sun acclimated leaves in both species. On the other hand, when comparisons were made on a per area basis, Chl a concentrations were greater in the sun than in shade leaves of tonka bean. In contrast, Chl b concentrations were higher in the shade environment for this species. No differences were observed in Chl concentrations per unit area in mahogany leaves. Carotenoid concentrations were higher for sun-acclimated leaves of mahogany, both on a per unit area and on a fresh mass basis. In tonka bean, higher carotenoid concentrations in shade leaves were only observed on a fresh weight basis. No differences were found between environments when carotenoid concentrations were expressed as a function of leaf area. Fluorescence variables (Fo, Fm, and Fv) were greater in sun leaves than in shade leaves of mahogany. In contrast, Fv and Fm, but not Fo, values were higher in shade acclimated leaves than in full sunlight-adapted leaves of tonka bean. However, there was a higher Fv/Fm ratio value for tonka bean in sunlight environments. We conclude that these species, classified as mid and late successional species, differ markedly regarding the utilization of photosynthetic pigments, increasing either light harvesting efficiency at low irradiance or protection against photosynthetic machinery damage in higher solar radiation environments.

HPLC analysis of tonka bean extracts.

Based on the results of GC-MS analysis, an HPLC procedure was developed for the determination of coumarin, dihydrocoumarin, melilotic acid (o-dihydrocoumaric acid), methyl melilotate, ethyl melilotate, 5-hydroxymethylfurfural and o-coumaric acid which are characteristic compounds of tonka beans. The presence of melilotic acid and ethyl melilotate in tonka beans has not been reported previously. Following HPLC analysis of tonka bean extracts produced in the laboratory and one sample of commercially available tonka bean absolute, evidence was provided that solvents used for production are decisive for the kind and amount of the compounds detected.

Distribution and Behavioral Ecology of an Arboreal `Tarantula' Spider in Trinidad

The Theraphosid spider Avicularia avicularia is reported to be widely distributed in Trinidad. A population in 2.2 ha of an abandoned tonka bean plantation was studied for 18 months. Juvenile spiders lived between the leaves of low growing plants. Most older immatures and adult females constructed camouflaged silk retreats at a height of between 1.5 and 3 m on tree trunks. Most inhabited trees accommodated single individuals. Dispersion was aggregated with a bias towards larger trees. The population density of long-term residents and vagrants was estimated to be between 13 and 30 ha-'. Diel activity was closely correlated with changes in light intensity at dusk and dawn. Ecdysis, reproduction, and associated weight changes were strongly seasonal, adult males appearing in the latter part of the dry season and young being born in June and July.

Glucosides of coumarinic and o-coumaric acids in the tonka bean.

The beta-glucosides of coumarinic and o-coumaric acids were detected in extracts of cotyledons, exocarps, and seedling leaves of the tonka bean. The existence of these compounds and the presence of a beta-glucosidase having specificity for coumarinyl glucoside suggest that the tonka bean synthesizes coumarin by a pathway similar to the one found in sweetclover.