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

摘要

In recent years Central Amazonia has experienced considerable effort to establish sustainably managed plantation systems. In the much favoured polyculture systems trees producing high quality timber are also considered to some extent. True mahogany (Swietenia macrophylla King) and the closely related Andiroba (Carapa guianenis Aubl.) are especially attractive in this respect. However, little is known about their ecological adaptation strategies, in particular with regard to the tine root system. In this study the anatomical 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 drought. Carapa guianensis produces cells with a distinct suberin layer and thick "U-shaped" secondary walls as well as "pad" cells which seem to direct the influx/efflux of water and nutrients. On the other hand, Swietenia macrophylla produces only very moderate "U-shaped" exodermis cells with a delicate suberin layer and also thin-walled "passage" cells without suberin. All 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 than that of Swietenia macrophylla.