Structure and functioning of oil cavities in the shoot apex of Metrodorea nigra A. St.-Hil. (Rutaceae).

This study investigates the histology and subcellular features of secretory cavities during the development of the shoot apex of Metrodorea nigra A. St.-Hil. in order to better understand the functioning of these glands. This Rutaceae species is a very suitable model for studying secretory cavity life span, since the shoot apex exhibits both dormant and growth stages during its annual cycle. Shoot apices were collected during the dormant and growth stages from populations of M. nigra growing under natural conditions. Materials were processed using standard techniques for light and electron microscopy. The secretory cavities originate under the protodermis, and their initiation is restricted to the early developmental stage of shoot organs, which are protected by a hood-shaped structure. Secretory cavities have a multi-seriate epithelium surrounding a lumen that expands schizolysigenously. Oil production begins before lumen formation. When the shoot apex resumes development after the dormant stage, the glands remain active in oil secretion in the developing shoot apex and fully expanded leaves. The mature epithelial cells are flattened and exhibit very thin walls, large oil bodies, leucoplasts surrounded by endoplasmic reticulum, and mitochondria with unusual morphology. The tangential walls of the epithelial cells facing the lumen undergo continuous peeling. The vacuole extrusion appears to be the primary mode of release oil into the lumen, in an exocytotic way. The continuity of oil secretion is ensured by the replacement of the damaged inner epithelial cells by divisions in the parenchyma layer that surround the oil gland, likely a meristematic sheath.

Anatomy of the developing fruit of Metrodorea nigra A. St.-Hil. (Rutaceae)

The pericarp and seed in development of Metrodorea nigra were investigated structurally.The flowers and fruits in different stages of maturation were fixed in FAA 50 and cross-and longitudinally sectioned, according to usual techniques. The differentiated epicarp was represented by the periderm of subepidermal origin. The mesocarp was parenchymatous. The endocarp was sclerenchymatous and originated from the meristematic action of the inner epidermis of the ovary. The seed was endotestal and originated from an anatropous, bitegmic and crassinucellate ovule. The nucellus and the endosperm occurred in small quantity in the mature seed. The embryo was straight with thick cotyledons. The seed and the endocarp were ejected in the autochory process. The fruit was capsular and coccarium.

O pericarpo e a semente em desenvolvimento de Metrodorea nigra foram investigados estruturalmente. Flores e frutos em diferentes estágios de maturação foram fixados em FAA 50 e secionados transversal e longitudinalmente, conforme técnicas usuais. O epicarpo diferenciado é representado pela periderme de origem subepidérmica. O mesocarpo é parenquimático. O endocarpo é esclerenquimático e se origina da ação meristemática da epiderme interna do ovário. A semente endostestal provém de óvulo anátropo, bitegumentado e crassinucelado. O nucelo e o endosperma ocorrem em pequena quantidade na semente madura. O embrião é reto com espessos cotilédones. A semente e o endocarpo são dispersos por processo autocórico. O fruto é capsular e coccarium.

Anatomy of the developing fruit of Metrodorea nigra a. st.-hil. (rutaceae)

El pericarpio y la semilla en desarrollo de Metrodorea nigra fueron examinados estructuralmente. Flores y frutos enetapas diferentes de maduración se fijaron en FAA 50 y se seccionaron transversal y longitudinalmente, según técnicas usuales en estudios anatómicos. El epicarpio diferenciado está representado por la peridermis de origen subepidérmico. El mesocarpio es parenquimatoso. El endocarpio es esclerenquimatoso y se origina de la acción meristemática de la epidermis del ovario. La semilla es endotestal y se origina del óvulo anátropo, crasinucelado y con dos tegumentos. La nucela y endospermo aparecen en pequeña cantidad en la semilla madura. El embrión es recto y posee cotiledones de reserva. La semilla y el endocarpio son eyectados en el proceso autócoro que ocurre en la especie. El fruto es capsular, tipo coccarium.

Pericarp and seed in development of Metrodorea nigra are investigated structurally. Flowers and fruits in different stages of maturation were fixed in FAA 50 and cross- and longitudinally sectioned, according to usual techniques. The differentiated epicarp is represented by the periderm of subepidermal origin. The mesocarp is parenchymatous. The endocarp is sclerenchymatous and originates from the meristematic action of the inner epidermis of the ovary. The seed is endotestal and originates from an anatropous, bitegmic and crassinucellate ovule. The nucellus and the endosperm occur in small quantity in the mature seed. The embryo is straight with thick cotyledons. The seed and the endocarp are ejected in the autochory process. The fruit is capsular and coccarium(.