Anatomy and fruit development in Schinopsis balansae (Anacardiaceae)

Gonzalez, A.M. & Vesprini, J.L. 2010. Anatomy and fruit development in Schinopsis balansae (Anacardiaceae). Anales Jard. Bot Madrid 67(2): 103-112. Schinopsis balansae Engl. is a dioecious tree; reproduction is by woody samaras containing a single seed. Fruit set is high, even in isolated trees, empty fruits are frequent and account for a high proportion of the total fruit production. To describe the anatomy and the ontogeny of-seeded and seedless fruits, flowers and fruits at different development stages from bagged and pollen exposed flowers were studied. The development and the anatomy of the pericarp in seeded and parthenocarpic fruits did not differ. It consisted in an exocarp formed sensu lato from the external epidermis of the ovary and some layers of the underlying parenchyma. The mature mesocarp was constituted by a sclerified tissue and lysigenous channels. The fruit is of Anacardium type: the endocarp presented three sclerenchymatic and a crystalliferous layer. The endocarp development was also sensu lato because it was formed from the epidermis and the hypodermis of the carpel. This organization agrees with the only species described in the genus: S. haenkeana Engl. Schinopsis balansae is able to produce parthenocarpic fruits in the absence of pollination. Empty fruits from free exposed flowers presented embryos arrested at different stages, although total absence of an embryo was the most common condition. Parthenocarpy seems to be a plesiomorphic trait within the Anacardiaceae, but regardless of its origin, the maintenance of empty fruit production in a wind-dispersed samara is difficult to explain. Whether parthenocarpy has an adaptive value, or is an evolutionary constraint remains unclear in Schinopsis.