Ontogeny and the concept of anoxia-tolerance: the case of the Amazonian leguminous treeParkia pendula

Abstract

WVith the advent of snow melt in the Andes and the commencement of the rainy season in the Amazon, the water level of the rivers rises 10 m or more (Furch & Otto 1987) flooding extensive areas of tropical rain forest for up to 8-9 months per year (Worbes & Junk 1989). The variations in predictability and regularity, as well as the differences in nutrient concentration of the waters of the distinct rivers involved, led Prance (1979) to name seven different types of Amazon forests subject to inundation. These distinct types of flooding resulted in the present existence of a mosaic of habitats in the Amazon flood plains, determining plant distribution and species diversity (Junk 1989). In this region, some species have developed different ecotypes and a number of genera have evolved different species to colonise distinct habitats. A typical example is the pan-tropical genus Parkia: out of 17 species described for the Neotropics (mostly tall trees), six are widespread (although three of these are infrequent) and, according to Hopkins (1986) the remaining II have a restricted or very restricted distribution. The specific habitat occupied by each of these species, ranges from coastal vegetation between beach and rain forest ('restingas') to savanna-like vegetation ('caatinga' and/or 'cerrado') and from periodically flooded areas ('igapos' and/or 'varzeas') to unflooded areas ('terra-firme' forests). This diversity of species inhabiting such a wide range of sites makes Pa-kia a genus of great interest for its ecophysiology and evolutionary history. In this context, the present work studies seed germination after long-ternm submersion and seedling growth under root flooding (up to soil level) and total submersion (whole plant) of the typically terra-firme species Par-kia pendula (Willd.) Benith. ex Walp., as was previously done by Coutinho & Struffaldi