The floral nectary of Hymenaea stigonocarpa (Fabaceae, Caesalpinioideae): structural aspects during floral development.
BACKGROUND AND AIMS: Considering that few studies on nectary anatomy and ultrastructure are available for chiropterophilous flowers and the importance of Hymenaea stigonocarpa in natural 'cerrado' communities, the present study sought to analyse the structure and cellular modifications that take place within its nectaries during the different stages of floral development, with special emphasis on plastid dynamics. METHODS: For the structural and ultrastructural studies the nectary was processed as per usual techniques and studied under light, scanning and transmission electron microscopy. Histochemical tests were employed to identify the main metabolites on nectary tissue and secretion samples. KEY RESULTS: The floral nectary consists of the inner epidermis of the hypanthium and vascularized parenchyma. Some evidence indicates that the nectar release occurs via the stomata. The high populations of mitochondria, and their juxtaposition with amyloplasts, seem to be related to energy needs for starch hydrolysis. Among the alterations observed during the secretory phase, the reduction in the plastid stromatic density and starch grain size are highlighted. When the secretory stage begins, the plastid envelope disappears and a new membrane is formed, enclosing this region and giving rise to new vacuoles. After the secretory stage, cellular structures named 'extrastomatic bodies' were observed and seem to be related to the nectar resorption. CONCLUSIONS: Starch hydrolysis contributes to nectar formation, in addition to the photosynthates derived directly from the phloem. In these nectaries, the secretion is an energy-requiring process. During the secretion stage, some plastids show starch grain hydrolysis and membrane rupture, and it was observed that the region previously occupied by this organelle continued to be reasonably well defined, and gave rise to new vacuoles. The extrastomatic bodies appear to be related to the resorption of uncollected nectar. (+info)
Phylogeographical structure of the neotropical forest tree Hymenaea courbaril (Leguminosae: Caesalpinioideae) and its relationship with the Vicariant Hymenaea stigonocarpa from Cerrado.
High-performance liquid chromatographic purification of oligomeric procyanidins, trimers up to nonamers, derived from the bark of Jatoba (Hymenaea courbaril).
Procyanidin oligomers with different degrees of polymerization (up to nonamers) were efficiently purified from the bark of Jatoba (Hymenaea courbaril) by using a recently developed chromatographic separation method. Purification relied on a hydrogen bonding interaction between phenolic hydroxyl groups of the procyanidins and polyethylene glycol (PEG)-coated resin in a packed column. The individual procyanidins were identified by using electrospray ionization mass spectrometry (ESI-MS) and verified by a thiolytic degradation analysis. Our results demonstrate that Jatoba bark contained a large amount of procyanidins from monomer to nonamers or higher polymers composed of only B-type linked units (flavan-3-ol units linked through C-4 to C-8 (or C-6)) of epicatechin (EC) without gallate esters. (+info)
Evidence of higher photosynthetic plasticity in the early successional Guazuma ulmifolia Lam. compared to the late successional Hymenaea courbaril L. grown in contrasting light environments.