Fruit anatomy and seedlings of the mistletoe Psittacanthus schiedeanus (Loranthaceae)

Abstract

Fruits of Psittacanthus (Loranthaceae) mistletoes depend on frugivorous birds for seed dispersal; however, despite the importance of birds in their dispersal and distribution, the external fruit morphology and anatomy and seedling remain poorly studied. Here, we describe the fruit anatomy and seedling of host generalist Psittacanthus schiedeanus (Cham. & Schltdl.) G. Don (Loranthaceae), a mistletoe species occurring from Mexico to Panama. Fully developed unripe fruits and ripe fruits were collected, processed for microphotography, and examined to describe fruit external morphology and anatomy. The following parts were observed in fruits: exocarp, viscin layer, seed coat, and the polycotylous embryo. Longitudinal sections also show the inverted position of the embryo. The fruits of Psittacanthus schiedeanus contain a polycotylous embryo and no endosperm. The absence of endosperm in the mature seed and the massive cotyledons having the storage function for the germinating seedling await further Psittacanthus species comparisons to end the pretending controversy of the polycotylous embryo and between having or not having endosperm in Psittacanthus.