Germinação, desenvolvimento e resposta ao alagamento de macrolobium acaciifolium (benth.) benth. (fabaceae) de populações de várzea e igapó da Amazônia central

Abstract

Amazon floodplains represent 16% of all the 5.000.000 km² of the Brazilian Amazon, where the major floodable areas are várzeas and flooded forests (igapós). These two ecosystems feature very different characteristics in terms of physical-chemical water and soil: the várzea is flooded by nutrient-rich white waters, while the igapó is flooded by black waters with fewer nutrients dissolved. This difference is reflected in the soil of these areas, and in order to tolerate the stress caused by the decrease of oxygen during flooding times, plant species in floodplains developed specific physiological mechanisms. However, there are also limitations imposed by the physical and chemical of these two ecosystems, so that few species can be found in várzea and flooded forests, such as Macrolobium acaciifolium (Benth.) Benth., the specie by which we investigated the influence of várzea soil and igapó germination, growth and development of seedlings in greenhouse. It was analyzed the biometric characteristics of the seeds, the evolution of germination over time, the specific leaf area, the amount of nutrients in leaves and the amount of biomass in seedlings and individuals of várzea and igapó populations on its soil of origin and on vermiculite. In what concerns the origin of the seed, there was a difference only in thickness since the igapó seeds presented higher averages, while lowland seeds presented higher averages in weight, but there was no significant difference in the percentage of germination. The average length and weight of the aerial part and in the length of the root were higher in seedlings in the igapó than in várzea. No significant difference in the averages of root weight, growth and biomass was registered, nor in external morphology and survival rate with respect to flooding. There was no significant difference regarding the length and weight of the aerial part. The lowest average diameter was observed in floodplain individuals developed in igapó soil, and the average of the specific leaf area was not statistically different from each other. The amount of macro and micro-nutrients in the leaves of M. acaciifolium in a floodplain or igapó varied in both soil types and with respect to the origin, since the igapó individuals in an igapó soil, in general, presented more nutrients in the leaves compared to floodplain individuals. The results suggest that M. acaciifolium of igapó individuals are more plastic-prone to adapt to environmental conditions than individuals of M. acaciifolium in várzea.