Morphology, Anatomy and Ontogeny of Female Cones in Acmopyle pancheri(Brongn. & Gris) Pilg. (Podocarpaceae)

Abstract

The developmental morphology and anatomy of the female cones of Acmopyle pancheri(Brongn. & Gris) Pilg. (Podocarpaceae) are described and illustrated, based on observations, histology, scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) imaging. Ovulate development is typically podocarpaceous. Ovules are unitegmic, and horizontal or inclined upwards throughout ontogeny; the pollination drop is inverted because of the declinate micropyle. Ontogeny of the epimatium-ovule complex is acropetal, the epimatium developing first. A terminal, distal sterile bract creates a pollen-scavenging area. During development, the whole cone re-orientates through some 270°, and the seed realigns approx. 60° with respect to the receptacle axis. The ‘receptacle’ or podocarpium supporting the seed is formed by gradual fusion of initially free bracts. The structures adnate to these bracts represent homologues of ovuliferous scales; they bear vestigial epimatia which may develop into supernumerary ovules or non-functional epimatia. Thus, female cones ofA. pancheri are vestigially multi-ovulate. NMR imaging effectively and non-invasively revealed the three-dimensional arrangement of vascular bundles and resin canals in the cones.