Fine roots of Carapa guianensis Aubl. and Swietenia macrophylla King: Cellstructure and adaptation to the dry season in Central Amazonia

In recent years Central Amazonia has experienced considerable effort to est ablish sustainably managed plantation systems. In the much favoured polycul ture systems trees producing high quality timber are also considered to som e extent. True mahogany (Swietenia macrophylla King) and the closely relate d Andiroba (Carapa guianenis Aubl.) are especially attractive in this respe ct. However, little is known about their ecological adaptation strategies, in particular with regard to the tine root system. In this study the anatom ical structure and chemical characteristics of the fine roots of these two species were investigated and special strategies to resist drought periods are demonstrated. Especially the exodermis develops cells well adapted to d rought. Carapa guianensis produces cells with a distinct suberin layer and thick "U-shaped" secondary walls as well as "pad" cells which seem to direc t the influx/efflux of water and nutrients. On the other hand, Swietenia ma crophylla produces only very moderate "U-shaped" exodermis cells with a del icate suberin layer and also thin-walled "passage" cells without suberin. A ll other tissues of the Fine roots do not differ significantly between the two species. Both store reserve protein bodies in the large central vacuole of the cortex cells to sustain prolonged drought. In general, the special fine root system of Carapa guianensis appears better adapted to drought tha n that of Swietenia macrophylla.